hello everyone does anyone know any good bump steer kit for the FD3?

 

FDs dont have any bumpsteer unless you move the steering rack.

Yes, the companies that make swaps kits that move the steering rack sell bumpsteer kits to try to move the bumpsteer introduced out of the standard ride height range and into driop or compression stroke.

 

The only time bump steer has been an issue in any FD for us is when power steering is deleted or when the rack is moved for a jz swap as mentioned. Regardless of how low the car is, it still drives as it should which is a testament to how incredible the car is.

The bump steer kit we put in the cars that need it is the Hinson kit. It's absolutely required when deleting power steering or doing a swap that requires movement of the rack. It fixes it like a light switch.

 

"FDs don't have any bumpsteer unless you move the steering rack." 100% correct

"only time bump steer has been an issue in any FD for us is when power steering is deleted "
as long as the rack is not moved bump steer is fine. i depowered my FD rack in 1999 and since depowering it does not relocate it the bumpsteer dynamics are unchanged from OE.

 

How low is your car?

 

Out of curiosity, why would a lowered FD not need bump steer adjustment?

Do the arms and steering rods happen to be the same length?

Or is the bump steer curve simply so mild that lowering the car doesn't have a noticeable effect?

My car came with a KTS bump steer kit, and it makes me wonder why they installed it.

 

from what I've noticed, the power steering system dampens everything a GREAT deal. this is most evident when deleting it on a lowered car. its pretty bad actually. I'm no pro racer but i don't know that there is a bump steer issue at all on an fd of any height with power steering. as we have seen in recent years, a problem doesn't need to exist to have a solution lol so bump steer kits being available isn't necessarily a sign there is a bump steer issue.

 

People are conflating change in KPI and scrub radius on significantly lowered cars with true bump steer. True bump steer is change in steering angle through compression or droop with the steering locked due to packaging or design compromises. I think FDAUTO is conflating force feedback on road imperfections from scrub radius/KPI changes in non powered racks.

A decent designed front end will have the rack offset in F-R and vertical plane to match the arms on the hubs minimising the front/rear angular sweep and the vertical offset on the hub with the offsets and angles of the upper and lower arms through range of motion.

What may be being marketed at bump steer kits are more correctly described as camber gain in roll/bump kits that return lower control arms below parallel at ride height so that tyre presentation angle to road still corrects itself with body roll (these are usually most popular and effective on machpherson strut setups). This is why people running circiut cars very low use drop hubs so they can return the suspension linkages to factory ride height to retain original camber gain/anti-dive/squat characteristics.

 

when i say bump steer i am referring to the steering wheel changing direction with imperfections in the road. if there is a dip or a bump in the road, the steering wheel will quickly and sharply change direction forcing the driver to correct to maintain the desired direction of travel. the moment only last about a second. my understanding of what i refer to bump steer as is incorrect?

 

Bump steer is a specific design parameter as I described. It is the measure of change is wheel steering angle as the suspension sweeps through range of motion (with no change in rack/box input).

What you are describing is tramlining/force feedback, which is exacerbated by scrub radius and castor trail, that being of offset(s) of the theoretical wheel pivot line where it meets the road surface with the actual centre of force on the contact patch. This is also a design parameter and consideration. When we crank up camber and castor it probably is a bit more than ideal.

If you have a customer that only rips skids and doesn't do circuit or a lot of winding road stuff backing out caster will reduce the effect.

If you want to build some in depth understanding you may be able to get hold of some Optimum-G notes, otherwise the bible: Race car vehicle dynamics Book by William F. Milliken Jr.. Obviously you can pay for a copy but there are pdf versions floating around.

 

Hinson tramlining kit lol

Thanks for the clarification

 

A little stalking shows the OP probably has 20B, most 20B kits move steering rack down instead of using a new oil pan or setting engine back in car.

OP probably needs a bumpsteer kit, and a bumpsteer gauge set-up to set it up.