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Why Suspension Bushings Are So Damn Important
By Bassem Girgis

Removing the old suspension bushings is one of the most annoying tasks, but it is almost as important as replacing your tires.

Car Analogy

Bounce up and down at the track? I don't see how bushings would cause that.

I also wouldn't recommend polyurethane as the goto choice for track bushings. Actually, stock rubber is probably better than poly. There are good options for the track. Poly isn't really one of them.

Janus00

Can anyone recommend a decent bushing kit? should I just replace with all stock?

jackmugen02

Mugen and Spoon make complete bushing sets. They are currently on sale at RHDJapan too. I have a Mugen Rear Control Arm Bushing Set 52366-XGS-S0N0 for sale.

Car Analogy

If street only, yes, stay with stock...

arnoldp

Power flex makes poly bushings in two different durometers, and ballade makes spherical bushings. I got power flex race bushings and have yet to install them. Will make a post once I do.

THMotorsports

For the compliance bushing, I completely agree with you since it needs to be able to deflect on more than one axis. However, it was my understanding that the other control arm locations only see rotation on a single axis. As such, poly bushings would actually reduce binding. Feel free to correct me if I'm wrong, I would love to hear your input on why rubber is better.

DefSport

Rubber bushings act like a spring when they are twisted around their axial axis, but most importantly, don't have much internal friction as they do this winding up. Poly lets the inner steel bushing rotate, so no spring, but LOTS of friction. Friction in your suspension is bad, as it acts like a constant force resisting the suspension movement in whichever way it wants to go. This leads to a "rough ride" and poor handling over bumps.

Poly goes from "a little" friction when just installed and well greased to a ton of friction as it squeezes the grease out over time (usually in a few months or so). It's gradual, so most people don't notice how poorly their car now handles, but it happens in all poly bushing installations.

Spherical bearings allow very little friction, so they are great if you can deal with the impact harshness (which can be almost nil to very noticeable, depending on the joint and suspension design).

Fokker

The handling of my car with poly would beg to disagree with the above. I suffer no poor handling over bumps (or at all) and poor handling over rough surfaces would be more an issue of your spring/damper combo and its ability to cope with the irregularities in that surface. The ride harshness went up, but 95A is well beyond the factory ~45A; the trade off for the relatively rougher ride is that I get enhanced feedback from the car.

Car Analogy

It would be more accurate to refer to it as stiction. AKA static friction. The initial resistance to sliding motion until a certain threshold is exceeded.

Poly bushings indeed have more freedom of movement than rubber, and don't have a progressive spring effect like rubber bushings do. But they do have this stiction.

The result is big, sharp bumbs are actually more comfortable than stock, as these easily and immediately overcome the stiction threshold, and poly allows full suspension motion without adding any spring effect. But small bumps or just contours in the road, which with rubber would have shocks gently undulating up and down, might restrict shock motion completely, or at least cause no shock motion initially, then as force builds and finally overcomes stiction more sudden shock movement.

So big bumps more comfortable, small bumps less comfortable. But the real concern is that delay, then sudden movement of suspension. Just makes it harder for it to do its job well.

Poly works well on heavier cars that deliver more force to suspension with even small changes in road surface, that more easily overcomes the stiction.