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Hey all,

I’m not by any means new to the forum but am a new member. Having a first gen is, there isn’t much that hasn’t already been covered for me to post on. Anyways, right to the issue at hand which is bump steer after installing an ls400 big brake kit. Not out of disrespect for figs who I know is tried and true, but I went with Autosports Engineering for the eccentric caliper adapters as well as 17mm rca’s for the swap as they were about half the price. Everything went on great, no rubbing between the caliper and tie rod, everything seemed fine. The car is lowered on tein street basis z coilovers maybe an inch to an inch and a half. Not the best coils and I’d really like dampening adjustment, but I bought the car with blown out stock struts and needed something quick. I also run a set of 1 inch wheel spacers to clear the calipers on the stock wheels, and some 1/32 or maybe 1/16 rack spacers for a tiny amount extra lock. The rack and wheel spacers were installed prior to the brakes so I really doubt that they have any impact on this. As far as symptoms go, which persist after having the car aligned, I have some pretty terrible bump steer and self steer characteristics, sometimes I have to manually feed the wheel back from a turn, and sometimes it will self steer deeper into a turn by itself. It also wanders quite badly in a straight line, not in any particular direction, just constantly fighting your hand back and forth. As you can imagine this feels incredibly uncomfortable to drive and quite dangerous. I reached out to Autosports Engineering about this and they pointed me in the direction of “finding a suspension guru on Facebook” instead of actually giving me any information on the intended setup with the rca’s or things to check, which is why I’ve come here. I favor you guys’ intelligence compared to finding a Facebook group as I was advised to do. So, if you have any theories, let me know.

I’ve got a few current hypothesis but no way to really test them without spending $$$.

I noticed I’m running a bit more wheel spacer than others with the LS 400 bbk, so I could have possibly thrown off scrub radius too far. However, this would only be very noticeable during braking/acceleration causing a change in toe in/out.

I could not be low enough to take advantage of the rca and have induced bump steer somehow by raising the roll center above that at factory ride height.

I noticed my tie rod pickup point is above the rack putting the tie rod at about a 4 degree angle upward to the knuckle, maybe this could be a point that induces bump steer and correctable by drop tie rods?

Also, forgot to add, my current alignment specs are -1.5 camber, caster is within stock specs as with toe.

For anyone interested, I went with Autosports 17mm roll center adjusters and eccentric adapters, ebc yellowstuff pads, ebc usr rotors, 25mm spacers, as well as stop tech braided brake lines front and rear. Including buying a set of used calipers, rebuilding as well as painting them, I completed the swap for just around $500 which I feel was a pretty good deal. If anyone wants links to where I purchased anything from feel free to message me. I’ll post up some pictures of the finished calipers as well.
134090
 

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The wheel spacers exaggerate any movement of the wheel/tire, so you feel way more coming to the steering wheel. I'd take a look at your front control arm bushings first and then go from there onto the rest of the front suspension/steering setup.
 

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Your bump steer is because of the geometry of the steering rack vs steering knuckle. There is not a way to raise the rack. So you will need to do it with alignment. I would suggest looking at the number 2 control arms and replace the bushings with adjustable ones or adjustable arms. That way you can get more caster. to help with the issue.
 
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