Truck Tech - Nov-Dec 2011
Spring Clamp Conundrum
I had a hopefully simple question. I'm constructing a rears up front (RUF) pack for my 85 4runner and I need to put on new spring clamps at each end that hold the springs into place. Now Iím thinking about using some 3/4" flat bar and just bending it around them which should work fine. My concern is that the stock clamps look like they're pressed into the 3rd spring. How could I go about getting new ones in there?† I had planned on drilling out the old ones, getting a bolt that was short enough to fit perfectly flush in the hole and just welding it to the spring.
Not really sure if I should be welding to the spring or not???†† Can you give me any advice for ensuring those spring clamps don't go anywhere?††
And is there any science as to where you put the clamp?† I had planned on just putting it back on the 3rd spring although it will be a 6 spring pack, or possibly the 4th spring.
The "rear up front" spring swap is quite
popular on the
Because the rear springs are a softer spring rate than the fronts, you generally need to make up a custom spring pack using 5, 6 or more leaves to build up a workable spring pack to carry the heavier front end.† And that is where you ran into the issue of putting spring clamps on the new custom spring pack.†
Luckily, the spring packs you are tearing apart for separate leaves can also supply all the needed parts for the new spring clamps.† As you can see in the image below, the factory spring clamps are of two general varieties.† On the left is the taller clamp that probably serves as a sort of anti-wrap function where the clamp is attached to the stiff overload leaf on the bottom of the pack and as the axle twists the spring under acceleration, that overload tips down in back until the top of the clamp hits the top of the spring pack and stiffens it up.† And to the right is the more common bent clamp that holds the front and rear of the pack to the main leaf.
What I do is to recycle those factory clamp parts to make clamps for the new pack.† I use a flat pry bar to wedge in under the bent clamps to open them up enough to take the pack apart.† Then you can drill out the factory rivet if you don't intend to use the clamp on that particular leaf.† Then straighten those bent clamps into a squared U shape.† On the tall clamp, I just remove the bolt and sleeve for later re-use.
I don't like the idea of welding on the spring leaves as that will affect the heat treatment of the steel, although since this would likely be at the end of a shorter leaf, it may not be a big issue.† Also, drilling spring steel is difficult to say the least.† I have done so and find that carbide bits do a decent job with use of lots of oil and working up in bit size until the hole is the size you want.† Spring steel will work harden as you drill so you need to use lots of pressure so the drill bit stays ahead of the hardening steel.† But the best bet is to place a clamp on the end of a leaf that already has an existing hole in it.† You want the clamp some place in between the spring perch and the spring eyes on each end and encasing as many leaves as you can.† Closer to the eyes is better, but then the shorter leaves are unclamped, so you need to pick something that will work for your pack.†
I have my clamp on the end of the 5th leaf and about midway between the perch and eye.† If you consult my web page, you can see I used to use a taller spring clamp on the rear half of the spring pack.† This did serve to keep the leaves together side-side and allowed lots of spring droop as the leaves could separate if needed.† However, after about 10 years of running that setup, I had the main leaf break at the back of the u-bolt plate where that top leaf would bend up behind the axle.† This was partly due to not having enough or a radius on the end of the anti-wrap leaf I had on top of the main leaf (you can read all about that setup on the web page, above).† But the root cause was that the loose clamp allowed the rest of the leaves to separate too much under droop and left only the single 1/4" thick leaf to handle any torque applied to the axle.
So I changed to a tighter spring clamp setup.† Using the squared U shaped clamp, I simply put that clamp where the tall clamp used to be.† Just mark a location for a bolt hole in the two upturned ends of the clamp and drill a hole to accommodate the bolt and sleeve from the taller clamp (usually 5/16" or 8mm).† As you can see below, I left a small gap between the sleeve and the main leaf.† This still lets the leaves move on their own but not completely separate in droop.
And to attach the clamp, U use a simple flat head Allen screw and a lock nut.† Choose a screw head that fits into the recess that the factory rivet used to be set up.† I think I used a 1/4" screw, about 1" long on mine.† Then slip the clamp under the leaf then add a lock nut and trim the end of the bolt flush to the top of the nut.† This does leave the not exposed to scraping over rocks on the trail, but in 10+ years of use, I think I only once had to replace the bolt and nut.† If that is an issue, you could probably source some 1/4" rivets and use the factory setup.† I like the lock nut as I can snug it up if the clamp ever loosens and starts to rattle.† You can see below, that I also inserted a think disc of UHMW polyethylene under the head of the bolt to serve as an anti-friction disc on the end of that leaf:
And you can see on the referenced web page that I made a similar clamp for the front half of the spring pack.† The only difference is that I attached the clamp to the top-mounted anti-wrap leaf and the clamp goes down and under the rest of the pack.† I now find with both ends of the spring pack held more tightly together that it works just as well off-road but without the wildly separating leaves in back.† As a side benefit of that, I find a lot less noise with the spring, especially when backing up and hitting the brakes hard.† I used to hear lots of crunching sounds as the leaves to separate and come back together.† Now it is basically silent.
Hope that helps with your RUF spring pack clamping issues.
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