LiquidBlue

Are you guys finding a bump steer kit is needed when lowering your car 1" using lowering coil springs?

LiquidBlue

Found some old threads where people are discussing this issue.

https://www.thirdgen.org/forums/susp...ll-center.html

https://www.thirdgen.org/forums/susp...ints-good.html


Clearance concerns with extended ball joints
https://www.thirdgen.org/forums/susp...clearance.html

First hand account:
https://www.thirdgen.org/forums/susp...ml#post5154883

MoJoe

iTrader: (5)

Lowering springs doesn't change the relationship between the A-arm arc and the steering linkage arc, so the bumpsteer should not be any worse than factory. Although "normal range" for you is now more into the "stock compression" range of travel, so maybe. Also, the lowering springs should be stiffer to keep from bottoming out, and should reduce the normal suspension travel, which another factor towards "no worse than stock".

Since you are changing springs, this is a good opportunity to measure your own setup: With suspension reassembled sans spring, move the knuckle from full droop to hitting the bump stock, record the height versus the angle at the wheel mounting surface, and you will have your bump steer curve.
If you had a bumpsteer kit, you would then make adjustment and remeasure to find the best curve.

Good for theory, but sorry I don't have a definitive answer.

LiquidBlue

Thanks for your input MoJoe. Reading your response, and some of the other threads that I just listed make me realize how much I don't know! Got lots o' learn'in to do!

MoJoe

iTrader: (5)

Additionally, you can measure the curves with the steering to left, center and right to get the complete picture.

UMI Sales

Here's a good article on bumpsteer:

http://www.longacreracing.com/techni...e=Bump%20Steer

Craig

SlickTrackGod

Actually by adding lowering springs can and generally will change the bump relation of the tierods in comparison to the A-arms- why? because the travel range of the suspension is now lower and thus the length of the strut is smaller distance- measured from spindle to upper strut mount. The shorter this distance the greater dynamic increase of caster angle in compression travel. If you take a OEM height car at lets say +4 caster settings+ and lets take the same +4 caster setting on a car lowered 2"... then bump both of them into 2" compression travel? the lower car will have a shorter strut distance, thus the angle will increase quicker in dynamic range. This greater increase in dynamic caster will cause the spindle to pull up and rearward more in relation to the OEM car pulling up and a bit less rearward. That rearward swing can and generally does make the tie rod attached to it not match the A-arm swing and thus will create a toe-in gain in articulation. By lowering the static height of the tie rod will help neutralize the arch and changes so they stay within tolerances.

Dean

ps- in other words for a quick example- both start at 4* caster, at 2" bump compresson travel the OEM strut angle coukld go aprox 6*. the lowered strut angle could go to 9* caster . The steeper angle tilts the outer tie rod back in relation to the inner tie rod in lateral form. This tilting will shorten the length in geometric form of an arching circle.