Polyurethane bushing a bad idea for the rear camber arms.
 

A few months ago I replaced all of my car's bushing with the Whiteline Polyurethane ones and my Ichiba Camber kits with the SPL ones. The install/alignment was quite a headache but what was worst is what I saw over the weekend while I was underneath it.

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This is how they were brand new.
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You will notice that the SPL camber arms are contorted at the hub assembly side. Talking to SPL over the past couple of days they explained how this happens and why they have developed the spherical bearings.

As the suspension is compressed, the rear camber actually moves in two different axis. As a result the bushing needs to allow a rotating motion as well as twisting. The whiteline bushing being made of polyurethane is stiff and only allows rotating, therefore stressing the camber arms during travel.

To prevent this from happening again I will be replacing the whiteline bushing with the SPL spherical bearings.

Thanks SPL for the great support!

wow, that is bad but I guess to be expected since I have so little expecations from companies nowadays. I always wonder if companies like whiteline actually do research to see how cars react to their bushings or just throw them out on the market claiming good things. I guess there is a reason why the stock bushings have some flex. I do feel for you as either whiteline or spl should try to help.

Maybe its me, but just looking at the arm and bushing design makes it clear that the bushing articulates in multiple directions - which is something urethane bushings do not do.

I'm not sure Whiteline deserves all the blame here.

agreed

doesn't spl come with there specific bushing needed or do you have to buy them separately

You have to buy this entire set? http://splparts.com/store/product-info.php?pid34.html

I already spent almost $700 with them. Going to be looking at 2000+ just in bushings and arms without coilovers yet. :(

i know there is another thread going on about this but what would i need to buy if i wanted to replace all my bushing camber arms A arms mid links ect with spl parts
i dont think they make sub frame bushing ect

Just wanted to update everyone on this...

Initially my thought on seeing the damage was that it would be due to the urethane bushings on the knuckle. Urethane bushings allow a pivoting motion, but does not really permit a twisting motion; some amount of twisting motion is needed as the suspension arms move through its different arcs. As the urethane bushing "binds" up, it will over time fatigue or bend the control arms. For example, on the 240SX and 300ZX, they have been known to damage front lower control arms and rear traction rods.

However, I realized the next day that there was a more likely explanation for that exact damage seen on the OP's control arms, we believe now that the damage is from his dyno shop strapping the car down to the dyno using the camber arms. For those of you who are getting your cars dynoed, please make sure the shop does not use the control arms to strap down the car, they are not designed to take a few thousand pounds of load in that particular direction.

Nonetheless, I do not recommend urethane bushings for the control arms or knuckles, I have seen too many damaged suspension arms on other applications, and there is no real performance benefit - you are trading increased friction and binding for a slightly stiffer bushing. For those who do not want to upgrade to monoball bushings, we recommend sticking to the stock rubber bushings. For more reading about the differences between rubber vs. urethane bushings, this is a good link:

http://www.elephantracing.com/techto...nefriction.htm

For those who insist on the urethane bushings, I recommend you check your suspension for bind by removing the shock/spring, then moving the suspension up and down, it should move relatively freely through its full range of motion.

Get some vaseline in there, that'll loosen her up:naughty:

Binding is a separate issue from friction, lubricating the urethane bushings reduce friction but does nothing for binding.

Kuah, please answer a few questions for me.

I am about to purchase the SPL differential bushings. My rear upper is torn and it's got to be done. I also was planning on buying the entire Whiteline set for the Z. If I were to do this would I be wasting my money?

At some point in the future, I will do an entire suspension overhaul and plan to use SPL arms and possibly bushings.

If you were on a budget, but seeking track performance what would you suggest?

If your going to get SPL arms and monoball bushings just save your money with the whiteline stuff and only get their subframe bushings.

I would stick to the stock bushings on the knuckle, they perform well enough if you are not going all out with a all monoball suspension. With the monoball suspension, you are getting a more precise and predictable feel (at the limit) by reducing friction and eliminating flex in the bushings. With poly bushings, you get a suspension that feels stiffer (due to increased friction and bind more so than reducing flex) but IMHO alot less predictable.

There is also no real overlap in labor to do the knuckle bushings at the same time as the diff bushings. As terramask mentioned, you can do the subframe bushings, there is quite a bit of overlap in labor there and it would make sense to do that at the same time as the diff bushings.

Or you can go with the Nismo ones which are still rubber and still a bit flexible, but they are a higher durometer than stock.

Just a thought.

Thanks guys.

Kuah,

Forrest from my local shop, Pro Tuning Performance in Ft. Worth, should be calling you today to get some diff. bushings. Based on y'all's recommendations and theirs I am going to skip all the other bushes and just replace the diff. with SPL and the sub-frame with whiteline. In the future this car will become mostly a track car, and at that point I'll start getting monoball parts.

Thanks again for the help.