ashleygtir
New Member
not sure if im being stoopid but.................. what is bump steer? ive never heard of it.
bump steer?
- Thread starter ashleygtir
- Start date
A
another sunny
Guest
bump steer,when you lower a car especialy a pulsar under heavy cornering the outside front suspension is compressed the steering arm end(atached to the hub) will no longer be horizontal causing a toe out effect of about 2 degrees. You can buy a correction kit in the uk(power engineering?)but on aus sites they mention drilling out the tapered coller on the hub and rebolting the ball joint upside down thus solving the bumpsteer problem.
I am not sure of how legal this is though.
I am not sure of how legal this is though.
The learned men on the SR20 forum say this is too extreme for a road car. More appropriate for cars lowered by +60mm.another sunny said:
They have also fixed the camber correction caused by overlowering too by moving the lower ball joint.
I htough you might ask that 
and I didn't have time to write an answer. Not a simple concpet but I'll try to keep it so:
1. Bumpsteer is toe change that is caused under suspension compression.
2. You get this toe change becuase your toe is set when the lower arm is static, not moving.
3. Even in a standard car the the lower arm and steering rod follow a slightly different arc as they are pivoted from a different position.
4. As the arms move, they follow completely different arcs so you toe out under compression as their relative lengths change. (See point 2)
5. If you over lower your steering arm, you can still get excessive bumpsteer, you'll just be on a different part of the curve. If you loook at this (After a quick image search)
http://www.nationaltbucketalliance.com/tech_info/chassis/Bumpsteer/index.asp
Our suspension is like Example 2 (but worse as our arms are different lenghts too!), Nissan have put a lot of time into making the 2 arcs as close as possible with the bits they have in their parts bin. Lowering the car will only make it worse.
6. Given what we've got, you can't eliminate bumpsteer, you move your steering arm pivots so its arc of travel relative to the lower arm are as close as possible and the distance change between the two arcs is minimised. The only way to eliminate it is possible is if the axis are in the same horizontal and vertical location.
7. Unlike camber and toe, measuring bumpsteer needs professional equipment or is a complete pain as you need to take 10 measurments across the range of movement of compression and see how much toe changes.
8. Example of the extremes the SR20 race boys are going to: http://www.sr20forum.com/showthread.php?t=91930&page=3
9. If you did lower your car extermely for race conditions, you can correct the bumpsteer, unfortunatly this won't correct camber change you will also get. These guys are raising the lower ball joint relative to the lower arm to compensate and are (still) looking into manufactuing their own lower arms!
10. If you can understand what they are saying, some of these guys are professionals and have a lot of knowledge and experience with our cars. One of them has written many good articles in SCC using our suspension as an example.
Hope that helps from an informed amateur.
Jim
and I didn't have time to write an answer. Not a simple concpet but I'll try to keep it so: 1. Bumpsteer is toe change that is caused under suspension compression.
2. You get this toe change becuase your toe is set when the lower arm is static, not moving.
3. Even in a standard car the the lower arm and steering rod follow a slightly different arc as they are pivoted from a different position.
4. As the arms move, they follow completely different arcs so you toe out under compression as their relative lengths change. (See point 2)
5. If you over lower your steering arm, you can still get excessive bumpsteer, you'll just be on a different part of the curve. If you loook at this (After a quick image search)
http://www.nationaltbucketalliance.com/tech_info/chassis/Bumpsteer/index.asp
Our suspension is like Example 2 (but worse as our arms are different lenghts too!), Nissan have put a lot of time into making the 2 arcs as close as possible with the bits they have in their parts bin. Lowering the car will only make it worse.
6. Given what we've got, you can't eliminate bumpsteer, you move your steering arm pivots so its arc of travel relative to the lower arm are as close as possible and the distance change between the two arcs is minimised. The only way to eliminate it is possible is if the axis are in the same horizontal and vertical location.
7. Unlike camber and toe, measuring bumpsteer needs professional equipment or is a complete pain as you need to take 10 measurments across the range of movement of compression and see how much toe changes.
8. Example of the extremes the SR20 race boys are going to: http://www.sr20forum.com/showthread.php?t=91930&page=3
9. If you did lower your car extermely for race conditions, you can correct the bumpsteer, unfortunatly this won't correct camber change you will also get. These guys are raising the lower ball joint relative to the lower arm to compensate and are (still) looking into manufactuing their own lower arms!
10. If you can understand what they are saying, some of these guys are professionals and have a lot of knowledge and experience with our cars. One of them has written many good articles in SCC using our suspension as an example.
Hope that helps from an informed amateur.
Jim
Last edited:
S
SpaceDude GTI-R
Guest
Hi
So is it worth fitting a Bumpsteer kit to road cars that have not been lowered?
Thanks
Russ
So is it worth fitting a Bumpsteer kit to road cars that have not been lowered?
Thanks
Russ