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4Crawler Offroad Products

Custom Leaf Spring Shims, Blocks and Spacers


NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

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Contents:

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Introduction

On leaf-sprung vehicles, shims (or wedges) are often used to modify the angle between the spring perch on the axle and the leaf spring itself. The correction may be needed because of longer spring shackles tilting the pinion out of alignment, or to change from a single-cardan to a double-cardan drive shaft (for increased drive line angle capability), or to correct steering geometry (so your trucks handles better). An alternative to shims is to cut off the spring perches and re-weld new ones on at the corrected angle, but this is a lot of work and requires careful measurement to get things lined up properly.

Anyway, for whatever reason you need a shim, you do need one. And if you need one you probably need an exact angled one, not just the angle or two the shop has. When I needed shims, I found one shop that had 3° and 6°, and another that had 4° and 8°. All of these shims were aluminum, and not the nice strong billet aluminum, no they were cheap cast aluminum. Cast aluminum can be brittle, and it tends to fatigue or deform over time, and ultimately break. On the rear axle, this can be a pain if it happens on the trail, if it happens on the front axle, this can be downright dangerous.

Since I had only been able to find low quality cast alloy shims available and only in limited angles, I decided to make my own shims from a solid piece of mild steel, cut to the desired angle. Then a flat seat for the center bolt head is cut into the base to eliminate stress at that critical point. These shims are much more resistant to breakage than cast alloy shims. After locating a material source, developing the mfg. process, and forming a company to produce them, 4Crawler Offroad can now make these made-to-order shims available to others. If you want to "roll your own", click here for a VRML model of my shim design (5°). These shims are used to correct drive line and steering angles on leaf-sprung vehicles. Feel free to read my article on measuring drive line angles here before ordering. Finally, for permanent mounting, steel shims can easily be welded to the spring perch. No worries about shims breaking, twisting or falling out on the trail.

Lift blocks are similar to shims, except they are designed to add lift (to a spring over axle) or drop (to a spring under axle) and optionally may have a bevel cut in the top for pinion angle correction. Common aftermarket blocks use extruded aluminum sections. The thin wall material is prone to fatigue and cracking. 4Crawler Offroad can also make solid billet aluminum lift blocks with built-in angles. With the solid material, the blocks will hold up to the heaviest vehicles and loads.

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Custom Shims:

Below, you can see a few versions that 4Crawler Offroad has produced over the years:

Below are some examples of various shim styles, tapered blocks, relocation plates:

3 degree bolt-on steel shim 8 degree weld-on steel shim 2 degree shim, 3" wide Billet aluminum spacer/shim
A: 3° Bolt-On Shim
High accuracy shim pictured
B: 8° Weld-On Shim C: 2° Bolt On 3" (76 mm)
Wide
D: 10° tapered AL block
Shims w/ offset center bolt holes Spring Relocation Plates, 3/4", 1" Offsets 2.5" x 8" long shim Twin center pin Ford Shim
E: Offset Center Holes F: Spring Relocation Plates G: Extra long (2.5" x 8") shims H: Twin hole shim for
- Ford F150/Raptor model

Below is a closeup of some of the design details 4Crawler Offroad incorporates in the shims. First is the above mentioned center bolt head relief pocket. By creating a flat pocket for the head of the center bolt (on bolt-on shims) you prevent stress on the center bolt which could otherwise cause the head of the bolt to bend, as pictured in this photo. Also, each shim is stamped in 1 or 2 places with the angle it was cut to. This will come in handy down the road when you need to change angles for whatever reason. On several occasions, customers have run into trucks with existing shims (of unknown angle) where it is needed to add or subtract a few degrees. Without pulling the shim out, its very difficult to get an accurate angle off it. With the angle stamped into the end and the face, it should be visible in most situations.

Closeup of shim details Weld-on vs. Bolt-on shim
Closeup of shim details Weld-on vs. Bolt-on shim

In the image above-right, is pictured a weld-on and bolt-on shim with a spring center bolt in the middle. The weld-on shim has a center bolt hole large enough for the head of the center bolt to fit. The shim itself is designed to be welded to the spring perch, in effect becoming a permanent part of the perch. The bolt-on shim has a center bolt hole only large enough for the shaft of the center bolt to fix. The head of the center bolt then fits into the machined pocket in the shim and then engages the hole in the spring perch as normal. In this case, the shim becomes part of the spring pack.

Note the difference between the thin shims and the thick tapered blocks. In the shims, there is only a hole in the middle. In the blocks, there is a hole on one side and a pin on the other side. So, can shims be made with a hole/pin combination? Unless the center of the shim is thicker than 3/4" (19 mm) - 1" (25 mm), there is simply not enough room for a hole deep enough for the head of the center bolt (they can be up to 1/2" (12,5 mm) tall) and the pressed in pin, which needs to be 3/8" (10 mm) or so deep. Since all the "shims" are made under 1/2" (12.5 mm) thick, they can only be had in the thru-hole design. If the hole/pin design is desired, then a tapered block will be required.

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NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

Ordering:

4Crawler Offroad can machine solid steel axle shims, custom angles, 1°-12°, made to your specifications:

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NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

Standard 2" (50 mm) wide steel shims:

Style :

Hole :

Hole Size:

Angle:

Length:

CLICK HERE TO SPECIFY SHIM OPTIONS...">

Style :

Hole Size:

Hole :

Angle:

Length:

Order for US delivery Order for International delivery


Style:

Hole Size:

Style:

Order for US delivery Order for International delivery


Style:

Style:

Order for US delivery Order for International delivery


NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

Custom width steel shims:

CLICK HERE TO SPECIFY SHIM OPTIONS...">

Style :

Hole :

Hole Size:

Angle:

Length:

Width:

Style:

Order for US delivery Order for International delivery


Style:

Style:

Order for US delivery Order for International delivery


Style:

Style:

Order for US delivery Order for International delivery


NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

Steel lift blocks (1/2", 3/4" and 1" tall, standard 2" width) in bolt-on or weld-on lift blocks.

  • Cost: $25.00/pr. plus shipping and applicable sales tax.
  • Specify bolt-on or weld-on, length and height:
  • Style:

    Style:

    Order for US delivery Order for International delivery


    Order for US delivery Order for International delivery


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    Steel lift blocks (1/2" and 1" tall, custom width) in bolt-on or weld-on lift blocks.

  • Cost: $35/pr. plus shipping and applicable sales tax.
  • Some international shipments may cost more due to weight.
  • Specify bolt-on or weld-on, length and width:
  • Style:

    Style:

    Order for US delivery Order for International delivery

    Order for US delivery Order for International delivery


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    2" Wide Axle Relocation Plates (specify length in the Note field):

  • 2" wide, 3/8" thick
  • 5/8" locating pin and 5/8" holes offset 3/4" and 1" from center standard
  • Custom offsets (3/4" or more) and pin sizes available, specify in the order Note field
  • Default length is 4-3/4" long and available thicknesses of 3/8" or 1/2".
  • Custom lengths available, up to 6" long, specify in the order Note to Seller field
  • Cost: $25/pr. plus shipping and applicable sales tax.
  • Order for US delivery Order for International delivery

    And now available, low offset relocation places for those needing to relocate the axle less than 3/4". These plates will be 3/4" thick and allow center hole/pin offsets of 0" - 3/4". This is due to needing to have plate depth to drill a 5/8" center bolt hole 3/8" deep in one side of the plate (to accommodate the head of the existing center pin) and to seat the 5/8" center pin ~3/8" deep in the other side of the plate. Specify the offset of the single offset hole in the "Note to Seller" field of the order form.

    Order for US delivery Order for International delivery


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    Custom Width Axle Relocation Plates:

  • Over 2" wide, 1/2" thick
  • 5/8" locating pin and 5/8" holes offset 3/4" and 1" from center standard
  • Custom offsets and pin sizes available, specify in the order Note to Seller field
  • Default length is 4-3/4" long
  • Custom lengths available, up to 6" long, specify in the order Note to Seller field
  • Cost: $40/pr. plus shipping and applicable sales tax.
  • Order for US delivery Order for International delivery


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    Toyota Spring Perch Spacers:

    Style:

    Style:

    Order for US delivery Order for International delivery


    Style:

    Style:

    Order for US delivery Order for International delivery


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    Longer center bolts:

    Size:

    Size:

    Size:

    Add a pair to a shim order Order a pair for US delivery Order a pair for International delivery


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    Toyota e-brake lever extensions:

    Order a pair for US delivery Order a pair for International delivery


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    Made to order custom tapered or flat lift blocks:


    Ordering Notes:

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    Frequently Asked Questions:

    Below are some commonly asked questions along with answers. Please take a minute to browse this list and see if it answers your questions. If not, feel free to contact me...

    1. How do I know what angle to make my shims or if I even need shims?
    2. How do I figure out how long to make my shims?
    3. How do I figure out what width to make my shims?
    4. What's the difference between bolt-on and weld-on shims?
    5. How accurate are the shims?
    6. Which way do the shims go?
    7. How long will it take to get my shims after I order and how will they be shipped?
    8. What if I measure wrong, am I stuck with the shims?
    9. Is there any "volume" discount on shims?
    10. How do I order the shims and specify options?
    11. I only need a single shim, can I order just one?
    12. Are there any drawbacks to lift blocks?
    13. Do you make shims for other applications?
    14. What if I want a tapered or flat lift blocks made out of steel instead of aluminum?
    15. Will I need longer center pins/bolts with the bolt-on shims?
    16. What are the center bolt hole location and options?
    17. Ford F-150/Raptor pickups use 2 center pins, can I get a shim to fit that application?

    1. How do I know what angle to make my shims or if I even need shims?
    The best answer is that you would have measured all your driveline angle prior to modifying the suspension. That way you would have some baseline measurements to use to restore smooth operation after the modifications. Unfortunately, nobody seems to remember to measure before slapping on the new suspension, so you'll need to resort to one or more of the techniques below...
    - You might contact the lift supplier and ask them what angle shim they reccommend for your type of vehicle with their lift installed.
    Spring manufacturers should be more than happy to supply this information to you.
    - You may get lucky and find someone else (on a web forum or mailing list) who has done a similar modification to their vehicle (that is similar to yours) and find out what angle shim they used for their application.
    Luckily, the Internet offers a great resource in finding this sort of information. For example if you have an early Ford Bronco, here is a great link. That link was found with a simple web search like this.
    Short of finding out from someone else what angle shim is needed, the only real way to know is to measure the angles. Since you are even considering adding shims means you have somehow modified your vehicle. Either you have added lift, changed springs, installed longer shackles, moved spring hangers, etc. You need to get some simple measurements to determine if shims are needed and if so, what angle shim is required. For rear axles, you only have the worry about the angle of the pinion in relation to the driveshaft.
    How to measure the driveshaft pinion angles:
    Depending on the type of driveshaft you are running, the information on how to measure may be found here.
    Front axle pinion and caster angle considerations:
    For a leaf-sprung front axle, you can use the above measurements, but they only consider the pinion/driveshaft angles. IMHO, you really want to first address steering angles up front (unless you have a trail-only rig) first then worry about pinion angles. Afterall, if you have to choose between having proper steering geometry or a proper pinion angle (so that you can use 4WD at speed), I would choose proper steering angle any day? Why? Well if you can't drive the truck in a straight line on the road, having 4WD available at high speed becomes a moot point. I have had bad caster angle on my truck and I can tell you that the term "death wobble" is aptly named! When that front end starts hopping all over the road and seems to get progressively worse as you drive is not fun. Give me good solid steering anyway and I can live with a little front driveshaft vibration if I need to use 4WD at higher speeds every once in a while.
    So how do you measure the steering caster angle? Best bet is to go to an alignment shop and have them put your truck on the alignment machine and give you a printout of the angles. You'll get a list of toe-in, camber and caster as-measured and they may tell you what the angles should be. If not, consult your owners manual or a good repair manual for your vehicle. As far as what angle to use, its a direct relationship between the number of degrees your caster angle is off and the angle of the shim. For example if your vehicle specs +2° of caster and you are at +5° or -1°, you'll need a 3° shim, and just install it in the proper orientation to correct the angle.
    Here is a link to Toyota solid front axle steering alignment specifications. On the Toyota front axle, an angle of approx. 6° up (front of perch higher than the back)on the spring perch provides a decent caster angle (Note: this measurement is related to but not the actual caster angle). And at this caster angle, the stock front pinion angle will be tipped up ~5° from horizontal (or 85° from vertical). So every degree you tip the pinion up/down will result in the same caster angle change.
    It is not uncommon for the caster angle to be off different amounts on each side of the axle. If so, this means that the front axle housing itself is not quite aligned side to side or that it is slightly bent. Best bet is to get a shim to correct the average of the two angle errors. Short of cutting off one steering knuckle and turning it to align with the opposite side, its unlikely that you'll be able to "twist" the front axle housing by using two different angle shims. If you think about it, you have a rigid steel housing attached to two flexible leaf springs with some shims in between.
    And if you want to correct BOTH the caster and pinion angles at the same time, the only way to do that properly is to cut and rotate the steering knuckles on the axle to set the proper caster angle and if needed cut and relocate the spring perches (or add shims) to set the proper pinion angle. Here is a writeup on doing this modification on a Toyota solid front axle. On some axles, like the Dana 44, you may find that one of the spring perches is cast into the side of the differential housing and is therefore difficult to modify. In that case, you can either use two shims to change the pinion angle, or cut/relocate the separate perch and then add a single shim to the cast perch to set the pinion angle.
    Finally, with regards to shimming the front axle. If you have a steering setup with the tie rod and/or drag link above the springs, you need to be sure there is enough clearance over the springs for the steering linkage to pass when adding a shim. Since the shim will add thickness and raise the spring pack off the axle/perch, you'll need to ensure adequate clearance for the thickness of the shim.
    CV or double cardan driveshafts:
    One complication arises if you are correcting the pinion angle on a CV or double-cardan driveshaft. This is because as you change the pinion angle, the driveshaft angle is also changing. Luckily, it is relatively easy to determine the relationship of the two angles. Basically the angles change by the ratio of the respective lengths of the driveshaft and the pinion extension from the axle center line. Lets say that you measure the distance from the center of the axle to the pinion flange or u-joint yoke and find it is 12" (as measured on a Toyota 8" axle). And lets say the driveshaft measures 60" long from the t-case output flange to the pinion flange. This results in a 1 in 5 ratio, meaning that for every 5° of pinion angle change, the driveshaft angle will change 1/5 of that or 1°. This is easy to see if you sketch out the driveshaft and pinions to scale. Since the shim is tilting the axle at it's center line and the pinion sticks out away from that center line, it moves up and down as the angle changes. This means the bottom end of the driveshaft moves up and down by the same amount. But since it is much longer than the pinion length, the angle change is reduced by the ratio of the two lengths.
    For a practical example, assume a 20° driveshaft angle and a 10° pinion angle, with a pinion length of 11" and a driveshaft length of 55", again your measurements will likely be different. So this gives a 1:5 ratio of angle changes. So, starting with the 10° difference, we want to end up with the pinion angle 1° - 2° less than the driveshaft angle. So, installing a 7° shim, we would find that the pinion angle would increase from 10° to 17°. But at the same time, the driveshaft angle would decrease by 7°/5 or 1.4°, so it would end up at 18.6° (20° - 1.4°). This leaves an angle difference of 1.6°, which is within the 1° - 2° target we were shooting for.
    2-piece driveshafts (i.e. center support bearing):
    For applications with 2-piece driveshafts (i.e ones with a Center Support Bearing - CSB), there is often confusion about what to do about the CSB. Some folks think it is necessary to shim the CSB to correct the driveshaft angle. This is generally not something you want to do in all cases. Why? Look at the way the driveshaft is set up. The part from the transmission/transfer case output to the CSB is generally a single-cardan shaft, It has one or maybe two u-joints on it and generally is run straight at both ends. And since it is a single cardan shaft, the angles at both ends must stay equal for smooth operation. So, if you shim or lower the CSB, you are changing the angle of that shaft and that can lead to alignment issues and vibration.
    So one option is to set the upper u-joint and shaft to 0° and then look at the bottom half of the shaft only, it is either a single-cardan (u-joint) or double-cardan (CV joint) shaft and you just measure and correct the angles on that part of the shaft. So just treat the bottom half of the 2-piece shaft like any other driveshaft and forget the upper half. In other words, treat the two halves of the driveshaft as independent parts, separated by that CSB. So, if you made no changes that affected the transmission/transfer case to CSB (which is attached to the frame) part of the shaft, you should also not make any changes to that part of the drive shaft. If instead, you made changes that affected the CSB to axle portion of the shaft, then that is tha part you need to correct.
    Another option on a 2-piece drive shaft that has 3 u-joints is to treat the upper shaft section as sort of an extended CV joint. That is the two u-jopints on that section of shaft should be equal to each other and they should also align (i.e. they are in phase). Then the bottom u-joint, at the axle, is set to 0° operating angle relative to the drive shaft (i.e. the pinion u-joint "points at" the carrier bearing u-joint). But if you have a 2-piece drive shaft with 3 u-joints, one of those u-joints should be at 0° and the remaining two should be at equal and opposite angles. So pick the u-joint that is closest to 0° and then set the other two u-joints to equal and opposite angles. It all depends on how the drive shaft was designed and set up at the manufacturer and how you have modified the vehicle (if applicable). But in any event, if you have 3 u-joints on the shaft, eliminate one of them by run ning it at 0° and then just worry about the remaining 2 u-joints.
    Traction Bar considerations:
    If running a traction bar, of some sort, that limits axle wrap, then the only real consideration to make is that you would want to set the lower u-joint angle to the ideal angle for your type of drive shaft. That is you don't leave the pinion 1° - 2 ° below the ideal angle. So for a single cardan shaft, you would have both u-joint angles the same and for a double cardan shaft, you would have the lower u-joint angle at 0°.
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    2. How do I figure out how long to make my shims?
    4Crawler Offroad does not have a master database of all possible vehicle and axle combinations (we tried to do this but it became sucha mess trying to keep track of every possible combination, that the data was not reliable). And by the very fact that you need to add a shim, you have a modified vehicle, the axle may or may not be stock, the perches may or may not be original, and the axle itself may be a hybrid of several different axle components.
    You'll want the shims to be about the same length as the spring perch on your vehicle's axle, which is very easy to do. One way to measure that is to get the distance between the u-bolts (length and width). If the axle is separated from the springs, just measure the spring perch directly. And no need to get the length measurement to the nearest 0.001" or 0.01mm, usually to the nearest 1/4" or 1/8" is fine (3 - 6mm). On some vehicles, spring perches can be difference lengths (especially on front axles). If this is the case, you would want to use the longest perch length measurement, and let the other shim hang over the ends of the perch. Shims can be made different lengths if requested, at an additional cost of $10.00, if desired.
    So why does the length of the shim matter? It should match the length of the spring perch. If it is too short, the spring may not make contact with the shim along it's full length, since it may hit the end of the perch sticking out past the end of the shim. If the shim is much longer than the perch, the thin end of the shim will likely just bend down around the end of the spring perch and be ineffective. Likewise, for any given angle, the longer the shim, the thicker the material it must be cut from is. Since most applications desire as thin a shim as possible (especially in a spring-under-axle situation), specifying a 6" long shims, for example, where a 4" shim would be sufficient may in fact double the thicknes of the shim.
    For example on the Toyota mini-truck axles, the rear spring perch is approx. 4-3/4" long, so the shims would be cut 4-3/4" long for the rear axle. However, some folks replace the stock spring perch with a u-bolt eliminator kit, such as the one AllPro Offroad makes. That kit uses a 6" long spring perch, so that is how long the shims should be.. The front Toyota mini-truck axle spring perches are approx. 5-1/4" long, so that would be the proper length for the front mini-truck axle. Other vehicles probably have varying length spring perches, so don't use the above numbers, grab a tape measure and find out for yourself.
    There is no "standard length" for a spring shim or rather there are many standard lengths! 4Crawler Offroad has shims have been made in lengths from 3-1/2" to well over 6" long. So bottom line, how long is the spring perch (front-back) on your vehicle's axle (rear or front) to the nearest 1/4" or so. See below for the measurment in question (note this is a modified Toyota rear axle spring perch, stock length is 4-3/4", this one has had 3/8" extensions welded to each end to make it longer). In this case the shim length would be about 5-1/2" long:
    Spring perch length
    Spring perch length
    Then see the following question and answer about shim width vs. spring vs. perch width.
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    3. My springs are more (or less) than 2" wide, what width shim do I need?
    You really have 2 options, one is to run the standard 2" wide shim, the springs really won't "know" the difference. If you look at the spring perch itself, it probably has rounded edges resulting in a flat area that is only about 2" wide. However, 4Crawler Offroad can make shims to the match the width of the springs and/or perch if desired. There is an additional cost for shims over 2" wide due to the additional material and labor required to manufacture them.
    For example, my Toyota 4Runner has springs that are 2-3/8" wide. I run 2" wide shims and they work just fine. A full width shim might resist twisting a bit better since it would be trapped in between the u-bolts, or I can even fit a 2-1/2" wide shim in between the u-bolts as the perch itself is 2.5" wide. So what is the "correct" width to use? That's why this is an option, you order what you want.
    On a vehicle like the Toyota Landcruiser that uses 2-3/4" springs or a full size rig with 3" wide springs, a full width shim probably makes sense. To put it another way, if its worth the additional cost (to you), get the custom width shim, if not, get the standard width.
    Also, some vehicles have spring perches much wider than the spring. For example, some early 1990s model Toyota pickups use a rubber lined metal clamp around the springs (the purpose of which is not known) and thus have a perch that is perhaps 1" wider than the actual springs. To add shims to this vehicle, you generally need to remove the clamp and then use a regular width shim. It would not really make sense to use a 3-1/2" wide shim on a 2-3/8" wide spring. Same story with some of the u-bolt eliminator kits, they have a perch that is much wider than the spring to allow room for the clamping bolt nuts to ride below the perch.
    On a related note, why do the custom width shims cost more than the standard width shims? There is more material (and waste) involved in the production of the custom width shims and also more labor. The standard width shims are cut from lengths of 2" wide flat bar to the exact length needed. On the custom width shims, they are cut to width out of 6" wide flat bar then cut to length. Any excess is scrap. The extra time and labor to make a 6" x 1" cut in steel is significant as well. Finally, with the standard width shims, 4Crawler Offroad often will make several copies of the shim if the length and angle are common. With the custom widths, the extra variable means its unlikely that exact combination will come up again, so each pair of shims is made to order.
    See pictures below for examples of measuring the width of the spring perch and the width of the spring. In this case the spring perch measures about 2-1/4" wide, the spring is abount 2-3/8" wide, so you could use a 2", 2-1/4" or 2-3/8" wide shim for this application, your choice:
    Spring perch width measurement Spring width measurement
    Spring Perch Width Spring Width
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    4. What's the difference between bolt-on and weld-on shims?
    In short, for the shim to do it's job, it must sit between the leaf spring pack and the axle/spring perch. However, the shim will not sit there all by itself, so you either need to attach it to the spring pack or to the spring perch. With the bolt-on shim, you use the center pin/bolt in the middle of the spring pack to also hold the shim in place. Essentially the shim becomes just like another leaf on the spring pack. In a spring-over-axle setup, the shims go on the bottom of the spriong pack, in a spring-under-axle setup, the shims go on top of the spring pack. With the weld-on shim, you weld the shim to the spring perch on the axle, thus the shim becomes part of the axle. With spring-over-axle, the shim is welded o the top of the spring perch, with spring-under-axle, the shim is welded to the bottom of the spring perch. WIth both bolt-on and weld-on shims, the shims still end up located between the spring pack and the spring perch.
    Both types of shims are made of mild steel. Below are some of the main differences:
    1. Bolt-on shim has a small center bolt hole (typically 3/8" or 10mm) for the shaft of the center bolt, the weld-on shim has a larger hole (typically 5/8"or 17mm) for the head of the center bolt.
    2. Bolt-on shim will have a pocket machined into the angled side to eliminate the angle for the center bolt head, allowing it to sit flat. This eliminates the stress riser in the center bolt that would otherwise be caused by the head of the center bolt being tightened against the angle of the shim. The weld-on does not have this.
    3. Bolt-on shim is typically shipped painted to prevent rust, the weld-on shim is shipped unpainted to allow welding it to the spring perch.
    4. A bolt-on shim may require a longer center bolt to hold it to the spring pack. If the extra length of your center bolt is less than the thickness of the shim, this would be the case. Longer center bolts are available above. A weld-on shim of course will not require any changes to the center bolt (or even removing it from the spring pack for installation), since the head of the center bolt simply fits into the hole in the shim to locate the axle and springs properly.

    A bolt-on shim can always be converted to weld-on at a later time:
    Simply drill out the center bolt hole to accommodate the head of the center bolt and weld it to the perch.
    Which type of shim would be best for your application? Well, that is all up to you. Both types will work equally well. Some considerations:
    1. If you do not have access to a welder, then the bolt-on shim is the best style for you.
    2. If are unsure of the exact angle shim you need or have plans to change your suspension at some time in the future, a bolt-on shim is easier to change out down the road.
    3. If you are sure of the angle shim you need and plan no future changes and want a more permanent installation, a weld-on shim, once welded to the spring perch, essentially becomes part of the axle.
    Here is a picture showing the differences, weld-on to the left, bolt-on to the right and a typical center pin in between the shims. Note how the hole in the weld-on shim is slightly larger than the head of the center pin, while the hole in the bolt-on shim is the size of the shaft of the center pin.
    [return to the FAQ section]

    5. How accurate are the shims?
    4Crawler Offroad can typically machine the shims to within +/` 0.5° tolerance. Shims are checked after machining with a digital angle gauge to ensure they are within this tolerance. Both shims are typically cut from one block of material so the angles are identical between the pair. This is typically more important than the exact angle. On thickness, 4Crawler Offroad tries to get the two shims within 1/16" of each other, and within 1/16" variation in thickness across the face of the shim
    4Crawler Offroad can also make shims for Toyota front axles where the 10mm offset in spring perch heights can be built into the shim, making the driver's side shim 10mm thicker than the passenger side shim. We can do other thickness differences as well, within the material dimensions.
    If concerned about the slight difference in thickness, measure the ride height of both sides of the vehicle and place the slightly thicker shim on the low side for a spring-over-axle or on the high side for a spring-under-axle application.
    While this tolerance is typically fine for 99% of the customers, some folks need higher accuracy. If your application depends a high accuracy shim, you can order the item below along with your shims to get shims custom machined to be typically within 0.010"-0.020" in thickness of each other, and the angle within +/- 0.2 degrees (whole angles only and shims of 6" length or less - see note below).
    If you are the type of person looking for shims with a mirror finish and tolerances of +/-0.001", you might want to look elsewhere for shims, as you'll likely not be satisfied with these. We make these shims to fit a practical application and once installed, they are nearly invisible, so surface finish is not a design factor. And since there is generally a bit of leeway in angle/length/width of the actual shim installed. raising the machining cost by performing extreme high precision operations does not really make sense. We try to offer a custom made and serviceable part for a reasonable price.
    Cost is $15.00 to cover the additional machining and setup time (note this option is only applies to one set of shims (per option) and you must specify it at the same time the shim order is placed):

    If you already have a set of shims and want them machined to a tighter tolerance, you may return the shims (US orders onnly) for re-work as noted below (cost $15.00/shim + return shipping), or you may have a pair of shims machined down to a thinner angle (for example from 4° to 3°): This option applies to angle changes of a few degrees. For angle changees of more than a few degrees, the better option is to order a new pair of shims as there may not be enough metal in the shims for the new angle:

    Shim re-work, US shipping Shim re-work, International shipping
    Note: The high accuracy option does not apply to any of the high angle or extra long shims with the laminated construction. This is because the laminated joints tend to get torn up by the milling cutter. We can do this operation on the billet aluminum shims and blocks because they are constructed of a single piece of material.
    [return to the FAQ section]

    6. Which way do the shims go on the axle?
    It all depends on which way you want the axle to rotate and how your axle sits on the springs. Its easiest to think of the springs as being rigid and fixed. Then visualize the axle being separate from the springs and one solid part, that pivots about the springs. Then, depending on which way you need to rotate the pinion to correct the driveline angle, think of grabbing the axle and turning it (and the pinion) to the correct the pinion angle. You should now be able to "see" a gap between the spring perch and axle on one end or the other, that's the side that the thick end of the shim goes in (i.e. the shim fills this "gap). One other trick I've found to help visualize this is to exaggerate the angles involved. Its hard to "see" 3° but if you imagine 30° its a lot easier.
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    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    7. How long will it take to get my shims after I order and how will they be shipped?
    These shims are custom made to order to *your* specifications. As such, they are generally not "in stock", since there would need to be thousands of different combinations of angle, length, width, bolt hole size and mounting style shims stocked to meet each and every possible order.
    Shims can usually be custom machined and shipped in 1-2 weeks (unless otherwise noted) depending on backlog. Normal shpping is via Priority Mail shipping from zip code 94088 which has 2-3 day delivery time in most of the US and Priority Mail International (to many countries, check the USPS.COM web site for service info.) which takes 6-10 days internationally. In the US, shims and blocks up to 1" thick are shipped in a Priority Mail envelope and insured via USPS insurance. In the event of loss or damage to the items, 4Crawler Offroad is happy to file an insurance claim on your behalf for the item. When the claim is paid by USPS, the shims or blocks will be re-made and replacements sent out. If you wish to have replacement parts sooner, you can order a replacement set and when the insurance clain is paid, those funds will be refunded to you for the original purchase. If you wish to have the items sent with signature guarantee in place of insurance, please indicate in the special instructions on the order form. If you wish more accurate tracking of the items, use the expedited Express Mail option below. If you wish to use a different carrier or shipping method, inquire below.
    Express handling and delivery (in the US, 1-2 day typical shipping time) is also available starting at US$25.00 additional for the shims and other parts, except for the larger custom tapered blocks. Please inquire on exact shipping costs for the larger items like that.
    Also, note that the standard shipping method (Priority Mail) only offers a delivery confirmation number, while Express Mail offers full package tracking information. So if you want detailed tracking information, select this shipping option.
    Order this item to upgrade the shipping on an previously ordered set of shims or center bolts.

    [return to the FAQ section]


    NOTE: Due to high order volume, it may take some time for production and shipments to catch up. Order backlog could be up to 4 weeks.

    8. What if I measure wrong, am I stuck with the shims?
    No problem, you can return the shims for credit against a new set. For custom and standard width shims (excluding the high angle and extra long variety) the credit against a new set of shims is $10.00. For the new set, pay the cost of the new shims, less the $10.00 credit and add return shipping and send back the old shims to 4Crawler Offroad. For shims/blocks with non-centered holes, or weld-on shims that have been welded on or other modifications such as high angle or extra long, contact 4Crawler Offroad for return/credit information. Generally for those types of shims, can only offer to re-machine the shims if possible.
    For the custom aluminum tapered and lift blocks and the fabircated steel blocks and shims, they are generally not refundable. We cut these blocks from a large block of billet aluminum or weld up separate pieces of steel to fabricate these parts to your specifications. Since these parts are so specialized, the chances of us being able to resell them in a timely manner is almost non-existant. We have an ever growing stack of shims that we have accumulated over the years in doing single shim orders or for exchanges and it is a very rare occassion where we can pull something out of that stack to fill a new order. And since we do at least 100 pair of shims to each pair of lift/tapered blocks, the odds of getting a match are at least 100 times less. We'll be more than happy to modify a block that you have ordered to a shorter lift height or different angle, etc., but if you tell us you want X, Y, and Z and we make you X, Y, and Z, then we have done our job. If you decide you no longer want the part, you might see if you can put it up on eBay or Craigslist or some venue like that. If you can find someone else who is looking for that very part, they are likely to offer you more for it thatn we can.
    [return to the FAQ section]

    9. Is there any "volume" discount on shims?
    For 2 (or more) pair of shims made to the same specification, there is a US$5.00 discount on the 2nd (and subsequent) pairs of shims, since there is a savings on setup time for the machining. This discount will be refunded upon shipment for on-line orders upon request, simply set the order quantity to 2 (or more) pair of the desired shims, specify the length, width and angle for the combined order. On multiple pairs of shims (of differing specifications) shipped to the same address, there is often a savings on shipping, over shipping them separately. You can also use the mutliple item order link at the top level web page.
    [return to the FAQ section]

    10. How do I order the shims and specify options?
    You can click on the "Buy Now" buttons above to order on-line using the PayPal service. If you have an account already set up on PayPal, you can just use it as-is, if you don't have an account set-up, you can do so on-line while ordering. You can use credit cards, electronic funds transfers and other sources for the funds as desired.
    You can specify any details on the parts order in the NOTE TO SELLER or Special Instructions link of the order form BEFORE hitting the submit order button, things such as the width and length of the shim, the angle, mounting style, etc. Be sure to select a good delivery address and double check that its correct. If you want the goods shipped to an alternate address, specify that CLEARLY in the note section. If you want to order multiple items or prefer another payment option, please contact 4Crawler Offroad via e-mail. And also, PLEASE BE SURE to give a working e-mail address to reply to. All too often 4Crawler Offroad is sent questions with invalid reply-to addresses, if we can't reply, you won't get an answer.
    [return to the FAQ section]

    11. I only need a single shim, can I order just one?
    Sure, 4Crawler Offroad can make single shims, cost depends on width, a 2" wide standard width single shim costs $18.00, a custom width single shim costs $30.00, add $8.00 for US shipping or $24.00 for international shipping and applicable sales tax (or order on-line below). Common use is on Dana 44 front axles with relocated long side spring perch, short side perch is cast into the diff. housing. Contact 4Crawler Offroad for details.
    --
    Order a single standard width (2" wide) shim:

    Style:

    Style:

    Single 2" wide shim; US delivery Single 2" wide shim; International delivery
    --
    Order a single custom width shim:

    Style:

    Style:

    Single custom width shim; US delivery Single custom width shim; International delivery

    [return to the FAQ section]

    12. Are there any drawbacks to lift blocks?
    In a spring-over-axle configuration, adding lift blocks does move the center of the axle farther away from the leaf springs. Since one of the leaf springs jobs is to resist the torque reaction of the axle to the tires in contact with the ground, moving the axle farther from the springs will increase the leverage of the axle on the springs. This can increase the likelyhood of axle wrap, which is a condition where the axle causes the springs to twist into an "S" shape, arching up in front and down in back, due to the axle torque. Whether this is a problem or not depends on the weight and engine power of the vehicle, the stiffness of the springs and the presence or absence of some sort of torque-countering device like a traction bar, kicker shocks or anti-wrap leaves. The taller the block the more likely wrap will occur.
    [return to the FAQ section]

    13. Does 4Crawler Offroad make shims for other applications?
    Sure, if you need a tapered shim for another application, feel free to contact 4Crawler Offroad for a quote. For example, tapered blocks/shims have been designed and machined for bumper and radiator mounting applications. Cost will depend on complexity and size of the part needed.
    [return to the FAQ section]

    14. What if I want tapered or flat lift blocks made out of steel instead of aluminum?
    Sure, no problem. Simply order the combination of a shim and lift blocks as needed to make up the height of block you want. The shim will typically be 1/2" center thickness, so account for that in the overall block thickness. For example if you wanted a 1" tall, 6° tapered block, order a 6° shim and a 1/2" tall block. Or if you wanted a 2" tall block with an 8° taper, order an 8° shim and a 1/2" tall block and a 1" tall block. Steel blocks are available in any width, lengths to 6" long and height increments of 1/2".
    Or if you want an axle relocation plate combined with a shim or a block, order the relocation plate and the shim or the block that you want and we'll combine them into one, or you can keep the relocation plate separate from the shim or block for ease of future changes. Just let us know which way you would like them to be set up when you order.
    The shim and block(s) will be machined and then welded together (for a cost of $8.00 per welded lamination) and shipped to you ready to install. If you want the block with a locating center pin, be sure to order one pair of lift blocks with the center pin installed.
    [return to the FAQ section]

    15. Will I need longer center pins/bolts with the bolt-on shims?
    The classic answer is that it depends. It depends on how much extra length your current center bolts have extending beyond the nut. And it depends on how thick the shims you plan to install will be. How thick the shims will be is a function of the angle of the shim and the length of the shim. Shims up to about 4 degrees will typically be 1/4" thick in the center, so if your center bolts have at least 1/4" of exposed thread then you should be able to re-use them. Shims over that angle can run up to 1/2" thick in the center. High angle shims can be thicker than 1/2" in the center, so factor in the thickness of the spring pack plus the thickness of the shim into determining the length of the center pin/bolt.
    [return to the FAQ section]

    16. What are the center bolt/pin hole location and options?
    As the name implies, the center bolt holes is typically drilled in the center of the shim to allow either the shaft of the center bolt/pin (for a bolt-on shim) or the head of the center bolt/pin (for a weld-on shim) to fit. However, some applications require a hole that is not located in the center. If this is the case, specify the center bolt hole location along with the other shim specifications in the "Special Instructions to Merchant" field of the order form. A non-center hole is often required where the spring perches on an axle have been redrilled to relocate the axle forward or backwards. And in some cases, you may have an axle where the spring perches have multiple holes in them to allow for several different axle locations. Often this is done with something like a relocation plate. If this is the case, the shims can be ordered with additional center holes, as noted below:

    And of course, you are more than welcome to order shims with no holes at all and then you can drill hole(s) wherever you want.
    IMPORTANT:
    When specifying an off-center hole(s), be sure to be clear about referencing the hole location.
    Examples of some imprecise descriptions are:
    Hole offset 1" forward of the center (we don't know which end of the shim you will be placing in front)
    Hole 1" from center (which direction off of center?)
    Hole 1" from the back (or front) of the shim (again, we don't know which end of the shim will be in front)
    So specify the hole is offset from or toward the thin or thick endl some examples would be center hole offset 1" towards the thin end or hole 1" from the thick end
    Also, hole locations are always given to the center of the hole, not the edge
    [return to the FAQ section]

    17: Ford F-150/Raptor pickups use 2 center pins, can I get a shim to fit that application?
    Some Ford pickup models use a non-standard leaf spring/spring perch with two 1/2" center pins spaced 40mm apart. So instead of a single hole in the center of the perch, there are two holes 20mm forward and 20mm back from the center of the spring perch. These spring perches are typically 3" wide x 5" long. We can add the additional shim hole to your custom width shim order with the order button below:

    [return to the FAQ section]

    If this is all too confusing to figure out, 4Crawler Offroad will be more than happy to consult with you on your specific application.

    [Return to the top of this page]

    References:

    U-bolts need to be properly torqued. You should consult your vehicle manufacturers recommendations, if that is not possible, then the following can be used as a general guideline.

    U-bolt Torque (from Rancho)
    U-bolt Dia. Torque (ft.lbs.)
    5/16" 15-18
    3/8" (10mm) 28-32
    7/16" 30-35
    1/2" (12mm) 65-80
    9/16" (14mm) 75-90
    5/8" 85-110
    U-Bolt Dimensions

    In the above image, you can see how u-bolts are specified.

    • A is the inner diameter of the u-bolt itself (not measured at the center of the bolt ends).
      • It corresponds to the maximum size axle tube it can fit over.
    • D is the diameter of the threaded bolt end.
      • Note that since most u-bolts use rolled threads, the unthreaded portion is likely to be a bit smaller in diameter than the threaded portion, due to the thread forming process pushing metal out to form the threads.
    • L is the length of the u-bolt, measured from the inside of the "U" to the end of the bolts.
      • It usually needs to be longer than the total of the axle tube diameter, the height of the spring perch, the thickness of the spring pack and spring plate and still leave enough length for the washer and nut to fit on top. U-bolts usually have an extra long threaded portion (which is often specified) that allows them to fit a wide variety of heights and then be cut to length.
      • If you find the nuts bottoming out on the u-bolt threads, you can stack a few hardened Grade 8 washers under the nut to gain some height.
    • Finally, the shape of the end of the u-bolt can be specified, the two common types are round and square.

    If needed, 4Crawler Offroad can special order a selection of replacement Grade 8 u-bolts. They include lock nuts and washers and run approx. US$20.00/ea. depending on size. Contact 4Crawler Offroad for more information.


    Installation Notes:

    Block the wheels and jack up the frame and put jackstands under it. Remember safety first. This will take the weight of the truck off the axles. You have to unbolt both sides before adding the shims. Unbolt the u-bolts carefully. If you did not take enough weight off the axle, the springs will ride down the u-bolts as you turn them. If that is ocurring, jack the frame up a bit higher. Once the nuts are off the bolts, pull the bolts and plate. Now your springs are connected to the frame at the rear perch and the front shackle. The springs are disconnected from the axle.

    For a spring-under axle setup, if you lower the frame, the axle will stay put because it is resting on the tires, and the springs will pull away from the axle a few inches. For spring-over axle, you can raise the frame a bit for added clearance.

    Clamping Leaf Springs
    Clamping Leaf Springs

    For a bolt-on shim, you can put a C-clamp on your springs ahead and behind the spring perch (see image above), clamping all the leaves securely. This will keep the spring pack from fanning out when you take the center pin out. Next, remove the nut on the bottom or top of the center pin. If the center pins are damaged, you might have to replace yours, or if there is insufficient excess length to accomodate the new shim. Put the shim in between the springs and perch (make sure the head of the center bolt is in the machined pocket in the shim) then install the old (or new) new center pin in and put the nut on. Pull it tight, but make sure your shim and spacer stay lined up.

    For single shims:
    If installing a single shims, for example on a Dana 44 front axle w/ rotated knuckles, you should try to align the hole in the shim with the hole in the other spring perch (that has been relocated on the axle housing) to ensure the center holes remain lined up. If you just align the center hole on the cast perch with the center hole on the shim, the angle of the shim will "push" the hole forward or back, depending on the shim orientation.
    For a weld-on shims:
    Place the shim on top of the perch, align the center bolt holes with a spare center bolt head or something of similar diameter. Then place weld beads on the thick end and sides as needed.
    For tapered blocks:
    Slip the block in between the springs and perch, ensuring the pressed in pin engages the hole in the spring perch and the head of the center pin engages the hole in the block.
    For axle relocation plates:
    You may also need to drill new holes in your spring/u-bolt plate to allow room for the end of the center bolt/nut to protrude from the spring pack in the new location. The relocation plate will provide the new hole in the spring perch for the head of the center pin, but if the u-bolt plate also has a hole for the end of the center pin, it'll need a new hole in it as well. You'll need to drill approx. a 5/8" (16mm) dia. hole for the center pin nut to fit in. A stepped drill bit (1/2" - 1" w/ 1/16" steps) works well for this is you need to buy a bit larger than 1/2" for the job. That way you can just keep enlarging the new hole until it is big enough to clear the end of the center bolt. And, to be honest, you may be able accomplish the same relocation by also drilling a new hole in the spring perch without needing to purchase the relocation plates. One issue you may run into with re-drilled perches is that there may be one or more existing holes in one or both perches that may be close to where you want to drill. Short of welding those holes closed, you'll have to adjust your relocation holes to match any existing holes, if possible. The relocation plates offer the advantage if being able to move the center pin holes forward or backward wherever you want them. The relocation plates are held in place by their pressed in center pins fitting into the spring perch center hole and then the spring pack center pin head fits into the hole in the relocation plate and finally the u-bolts hold the spring to the plates to the perches. You can weld the plates to the spring perch if desired, but that is not required.

    Lower the frame back down (or up) until the center pin pops into the hole in the perch. You may have to push and pull on the tires/axle a bit to line the center pin up correctly with the hole in the spring perch. Then, put the spring plate back on with the u-bolts back in. You should inspect your u-bolts and if the threads are damaged or the bolt appear stretched or fatigued, consider replacing them. You may also need to replace them with longer bolts depending on the thickness of the shim/block. New u-bolts are relatively inexpensive and reusing them is often recommended against. After re-installing the u-bolts, torque to the factory specifications (or use the table above). Check to make sure everything is lined up. Push and pull on the axle to make sure it is secure. Lower your frame back off the jackstands. Take it for a test drive. Go slow and listen for odd noises and then re-check the u-bolt torque after approx. 100 miles.

    Toyota e-brake extension installation.

    [Return to the top of this page]

    (Contact 4Crawler Offroad if interested in more information on any of these items)


    [Return to the main 4Crawler Offroad page... ]
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