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| Leaf spring ride quality |
Subject: Leaf spring ride quality
by Dodgeman on 2004/5/2 0:48:15
There has been a little discussion in another thread about an IRS under a 1200 coupe. This is not really a project to be taken on lightly, or by the faint of heart, bit i think that the real issue is ride quality, so here are a few observations, & your constructive input is encouraged.
Leaf spring cars came new, with interleaf rubbing blocks. These were intended to reduce the friction between the end of the spring leaves & the leaf above it.
After 30 years, these rubbing blocks have all worn away & very few people have replaced them. The end result of this is that the dry leaves, complete with a little rust between them, have a great resistance to movement between the leaves. This is called STICTION.
If your rubbing blocks have completely worn away, then give this a try. As an experiment, jack up the body your leaf sprung car so as to allow the suspension to sag. Prize the leaves apart a little & spray in some light lubricant. Perhaps some 20 weight oil.
Go for a test drive. Do NOT go racing just yet as you could find that ride quality has dramaticly changed & your shock absorbers may be much more worn than you thought.
If ride softness has improved, you have discovered one reason for harshness.
THE FIX?
You could buy a set of the rubbing blocks & replace them. I think that major suspension shops have universal types.
Another method is to remove the springs & dismantle them. Then go over the leaves with a belt sander to remove the rust & smooth out the roughness. Abrade only along the spring, don't do it across the leaves. If you want to lower the suspension, now's the time to have the springs reset.
Here's the hard part.
A popular trick at one time was to use teflon strips between the leaves, but urethane might be just as good & i think, more available. Check with some of the urethane bush manufacturers for availability. Once you have painted the spring leaves, assemble the spring with these thin, full length strips.
If you can get some suitable sized shrink down tubing, then use this over the spring, if not, then carefully wrap the spring with electrical tape. This is done to keep out the abrasive crud from the road, & to prevent the teflon/urethane from migrating out from the side of the spring leaves.
Reassemble into car using new urethane suspension bushes. If shocks are in the slightest bit suspect, replace with uprated types.
It all sounds like a lot of work, but it's a lot less work than engineering an IFS into a car that was never intended to have one. Its a job that most of us can do in a home workshop & the ride quality will be much less harsh. It may even be just what you were looking for.
It will cost a lot less too.
The full deal on the leaf springs makes them behave much more like coil springs, which have no stiction whatsoever, & this is the reason for the uprated shocks.
Try the oiled springs test & see how it feels.
OK, the forum is now open for constructive commentary
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