dapopa9

C6 Z06 Bushings

I'm guessing these shouldn't look like this? I think the rubber should probably be symmetrical on both sides of the control arm right?

My car only has a little over 20K miles and a few HPDE's on it. Guess I need poly, delrin, or spherical huh?


Anyone have a pic what they should look like installed?

..

lathrash

It appears those bushings look just like the way they do from the factory...

http://www.edmunds.com/car-reviews/t...alkaround.html

Solofast

Been discussed at length and there are zero cost fixes.

Here's the link, go to the bottom three posts on this page...

http://forums.corvetteforum.com/auto...s-options.html

Basically all you have to do is flip the rear bushing and it will be fixed. Full instructions are in the link. You can do both sides in an hour or two, easy peasy and it won't go bad after the fix. You don't need any special tools, just vise to put the ear of the arm in to take it out and put it back in.

Other options are T1 control arms, but they don't last much longer. If you go to poly bushings the noise and maintenance are a PITA.

dapopa9

Hmmm those pics do look very similar to mine. Seems very off that the front UCA bushings are different from front/back and also driver/passenger side. The LCA's on mine are also all different in terms of how much rubber is sticking out on each side.

I wonder if this is all by design or just sheer lack of strict tolerances?

Bill Dearborn

At this time the bushing looks fine. If the control arm was moving forward on the rear bushing it would also move forward on the front bushing which has not done. Check the LCA bushings since they are just as susceptible to moving. Then with a normal GM street recommended camber setting see how much caster you can get. If you can get the full range of caster the bushings are in excellent shape. If the UCA moves forward on the bushings that will kill your positive caster settings. If the LCA moves rearward on its bushings that will kill your positive caster settings. GM seems to have resolved some of the movements they had with the early C5 control arms since the bushings have a pretty stout flange at the outside of each bushing to resist forward or rearward movement of the control arms.

Bill

Solofast

Bill,

The problem is that eventually the control arms bend. Because the flange is on the front bushing, that takes all the load and after a while the front leg of the control arm bends and the rear one pulls off of its bushing. By flipping the rear bushing both arms share the load and it doesn't bend anymore.

If you are seriously tracking the car you should flip the rear bushing before the arms have a chance to bend and you will never have the problem and you will keep the caster that was intended.

hklvette

As Solofast describes, I flipped the rear bushings in my UCAs on my Y2K coupe which stopped them from "walking". Someday I want to pick up a new-in-box UCA and make a mold of it, then see how well or poorly the arms I have now fit in the "correct" mold.

The lower arms on a C5 will have the same problem with the LCA's front bushing walking out, or at least mine is. Before that happens you can flip the front bushing to put the "flange" on the rearward side of the arm to help distribute the load applied under forward braking.

The root of the problem is that the suspension does not appear to have been designed with the loads that R-comps and the stickiest street tires can make. I don't know of anyone who has seen this problem on the stock run-flats. The C7's bushing setup is an improvement and may be enough to keep everything in place, but don't be surprised if we begin to see them same issue with them.

mikeCsix

Interesting,

Would the UCA and LCA bushing movement also have an effect on toe? I have camber kits installed, ran six hpde's last year. I went in for new tires this year and was surprised how far toe was off. I thought it might be the rubber in the suspension that caused it.

yooper

Apocolipse

Considering it flexes most under hard braking then that would affect your toe for sure when it is most important to give the most amount of bite possible to slow down. Solofast seems to know his ****.

Soloontario

Few points about bushings. Obviously those of us who track our cars have both the UCA and LCA control arm bushings walk somewhat due to the issue with serious tires and brake pads.

In my case the issue is much more the LCA than the UCA and yes I can't really get enough caster in the car now. I had always thought that rubber bushings pushed into control arms were meant to stay put i.e all the deflection occurs in the rubber itself, while a poly bushing actually spins inside the control arm. (Hence the issue of making sure a rubber bushing mount is tightened when the suspension is in a neutral position to prevent pre-load)

I also understand that the issue with UCAs is likely related to the flexing of the rubber as much as the position of the flanges. I was NOT aware that the UCAs actually bent. Didn't think they had that much force on them. Not sure that flipping the flange for the rear UCA rubber mount would work and would like to hear from those who have done it. Too bad the Pfadt type bushings are no longer available.

Now to a second point, has anyone used poly in the LCA and stayed with rubber in the UCA? Strikes me that the LCA takes a lot more load than the UCA both front to back and laterally. Given that both rubber bushings will deflect, if the bottom is poly and the upper is rubber, wouldn't this be good to help maintain camber during lateral load? I.e you could use less static camber to maintain dynamic camber.

Solofast

Flipping the flange to the front works because without the flange flipped all of the forward load created by braking in the upper control arms is reacted by the front bushing. Once you flip the bushing the load gets taken by the rear bushing until the rear arm bends a bit and then the load is shared by the two bushings and the load drops to half in any one arm. At that point it doesn't bend any more because the load is half of what it was and the arms are strong enough not to bend anymore with the lower shared load. I've flipped the bushings on two cars that were tracked extensively and it works. One car I did it on was already pretty bad and it worked fine, restored the caster and the car was much better, eventually the bushing position evened out. The second one wasn't as bad and it still looks pretty good.

For a track day car I would flip the bushings on a new set of upper arms. That way the arms wouldn't bend and you wouldn't lose caster due to bending of the arms. It's so darn easy to do when you are installing new arms that it's crazy not to do it since it costs nothing and makes the arms last forever.

Yes, the lower arms have more load in them, but the lower bushings are a lot stiffer to start with, so while poly reduces the bushing deflection, it's effect is the same as it is replacing the upper bushings because they are so soft.

Soloontario

I gather that folks with poly bushings all round often feel their car is more stable under braking but if you replace both LCA and UCA arms with poly or delrin, don't you then need even more neg camber?

I am willing to try flipping my rear UCA rubber bushing although I am more concerned about my LCA rubber bushings walking to the rear of the car. How difficult is it to get the flipped bushing back into place in the UCA?

Solofast

Getting the bushings out is fast and easy. Just put the ear of the bushing in a vise and grab the arm and spin it off. Getting them back in isn't hard, there are two ways to do it. If you have a big C clamp or a press and a piece of tubing it can be pressed back in pretty easily. It isn't the force required, it's just that it's harder to get a handle on getting the ear thru the arm enough to grab it with a vise and then spin it back on.

It's been 4 years or more since I did it, but the other way to do it is to put the ear by the flange in a vise with it sticking up, put the arm on it and push down and spin it on a half a turn, take it out of the vise and clamp it again and spin it on another half a turn. Then when you are close to getting the right bolt spacing, spin it to match the front bushing in orientation so that both front and rear ears are flat against the chassis at the same time.

With poly bushings you don't need as much static negative camber since you don't lose as much due to bushing deflection. That is really the best thing about stiffer bushings, you don't need as much static negative camber so you get better braking since the front tires aren't as knocked knee'd as it is with the softer bushings.

froggy47

The lca's are magnitudes stronger/stiffer than the uca's. They don't bend as much.

Soloontario

Ok, another quick question, with the LCAs the bushings walk to the back of the car (wish there was an easy fix for that) . Why do the UCAs walk to the front or is it something different altogether?

Apocolipse

The moment created about the spindle when under braking makes the top push forwards and the bottom push back. It's a counterclockwise moment.

Solofast

Exactly..

Easier for the un-engineers to understand it this way..

Think of the brake caliper as being attached to the spindle and when it grabs the rotor the spindle tries to rotate and the control arms hold it in place. The top arms are pushed forward, and the lower arms are pushed aft..

froggy47

Tire rotates on rim.

Apocolipse

Which is why the tire stops the car.