The SPL parts look much more durable to me and I believe are lighter due to use of better materials.

SPL PRO SUSPENSION | 09+ Nissan 370Z Z34

http://cdn.splparts.com/large/SPLRTRZ34_0.JPG

This is pretty interesting. I had a 91 MR-2 turbo and it definitely had a bit of bump steer. I think this is more a case of the back end just getting a bit light though. Also the difference that Red_Zed got from ride height to full compression was only 1/32 not 1/16. So I do agree that there is some bump steer going on but it is barely an issue IMO at least in compression. What I would love to know is how much it changes in droop. My thought is that while it may not change much under compression, how much does it change when it is in droop after going over the bump and before it comes down and settles. I'll be getting a new set of tires in the next couple weeks and plan on getting the alignment redone. I'll try to see if they can find a way to get the suspension to a bit and see how it affects the suspension geometry.

The RE050a just wears fast, half worn at 4K is probably a little high, but not out of the norm

No, it changes a lot more from rest to compressed than it does from unloaded to rest. It's not a linear relation.

Red_Zed your measurements were taken from ride height to fully compressed right? So if it has less change from unloaded to rest and the change from rest to fully compressed is pretty minimal (~1/32 difference) would this kill the bump steer idea? I know it's still there on paper, but can the average person feel the difference of 1/32? I've gone over a few sharp bumps in corners at interstate speeds (one freeway interchange ramp really got my attention the first time i hit it) and i just assumed that it is the tires getting a bit light, not bumpsteer. My thinking was that with the bumps I've encounterd the backend hits the bump and as the back end rises a bit the rear wheels get unweighted just a little bit and it causes the lose feeling. I'm not a suspension expert though so I could be a bit or way off. Forgot to mention that i realize it isn't a linear change. But i was thinking that if it gains more toe under compression that under droop it would lose toe. Where are these bump steer gauges that you speak of? I would love to get a set to play with if they aren't too expensive.

I'm tracking these posts with great interest.

http://www.amazon.com/Longacre-Bump-.../dp/B000VAPZKO

I don't have my exact numbers in front of me, but I think the car lost less than 1/64 from rest to full up, though I could be off

wow, thats expensive if i'm just getting it to play around with. Also that isn't very bad at all imo if it changes from lets say ~3/64 to 6/64 (that would cover the change from full droop to full compression if my math is right), it seems that the toe angle is pretty well controlled.

Personally, my ideal would be less than 1/64 of gain for a street/track car. I'd prefer no gain (personally) for a car that spent more time on the track, though it would change depending on the layout. Much of this is preference, but pulling another 3/64s will upset balance when at the limit, especially if you are cpming from expansion out of the braking zone.

I purchased the Koni's because of this bumpsteer issue. When I initially installed them, I firmed up the rears by +3 (out of 8 max) and left the fronts at +1. Took it out for a test drive that day and I noticed a significant improvement, immediately. However, there was still a little bit of residual symptoms of bumpsteer during the test drive (it got a little wobbly on me).

After reading the subsequent posts in this thread, I thought I would try firming the rears a bit more. I turned them up from +3 to +5 and left the fronts alone. Today, I took it out to the twisties and had an awesome drive. This configuration, for me, eliminated the symptoms that used to scare the hell out of me. I highly recommend considering the Koni's ahead of the adjustable control arms.

good to hear, dAvenue! :tup:

Good to hear you got her dialed in. :tup:

Alright! Now we're talking. What did the Koni's cost (if you don't mind) and how did they affect the ride and handling overall?

They're ~$1k and improved the ride quality quite a bit. The damping is adjustable, so the ride quality will depend on the configuration you choose. For my setup of Koni and Eibach, the car holds a straight line when rolling over bumps and handles them graciously. I like the soft setting on the fronts because big bumps don't upset the chassis while the firm setting on the rears alleviates bumpsteer.

:tup: