could someone simplify bump steer for me and how it affects a car. was looking at a cheap bump steer measuring gauge to set it up at home? cheers

[Edited on 2/1/12 by daniel mason]

[Edited on 2/1/12 by daniel mason]

Bump steer is when as the axle moves from droop to compression the wheel turns/steers, in the ideal world no turning at all, you will notice when driving as the car will be twitchy on rough roads.

No need for a gauge, a length of wood or laser level will do

It occurs because as the steering rack and axle do not all pivot at the same point.

To see if you have it tie a length of wood to the wheel so it points out in front of the car, if you bounce the suspension and it wiggles left to right then bump steer is occurring.

To get rid draw an imaginary line through the bone chassis brackets, this line needs to go through the steering racks inner ball joint, I had to cut my rack down by 4" to achieve this when in the straight ahead position.

When I set mine up I removed the front springs and pulled and pushed the axle through its full movement then moved the rack until I had the optimum position.

Regards Mark

Bump steer is when the wheels steers due to suspension movement, you don't want any if possible.

Easiest way to check for bump steer is to take the spring off the shock absorber so that the wheel can be lifted and lowered through it's full movemnt range.

Then standing above the wheel lift it up and down watch to see if the wheel is steering noticeably.

If you do have excessive then you need to move or alter the steering rack to reduce it.

Davie

EDIT: Too slow - I also had to shorten the steering rack and housing and lengthen the track rods for book chassis and mk2 steering rack.

[Edited on 2/1/12 by daviep]

Bump steer occurs when the direction that the front wheels point in is affected by the position in their suspension travel. The consequence is that when you go over a bump (or a dip) the wheel points a different way which causes "bump steer". It is most disconcerting.

You can get it on either or both wheels.

The reason is that the arc of travel of the steering arms is different to the arc of travel of the suspension wishbones, which causes the steering arms to push or pull so as to steer the car as the suspension is compressed.

In my case I supported the chassis on blocks, removed the springs, and attached laser pointers on each front wheel (pointing forwards). Then I could move the front wheels up and down and watch how the spots of laser light moved on the fence. Ideally they shouldn't move. I ended up slightly moving my steering rack position. It is affected by things like toe-in, and in my experience is one of those things you sort of iterate on until it is correct.

The improvement on the road was considerable in my case.

I atached one of those cheap pen laser pointers to the axle spindal. With a big bit af cardboard on the garage wall and no spring on the damper I plotted on the card as I moved it from full droop to full compression. I repeated this several times moving the steering rack up and down on spacers.

I know this is on a Pilgrim Sumo, but the following should help how to measure bump steer.

http://www.bing.com/videos/search?q=bump+steer+youtube&docid=1312576045516&mid=2E550B6B5BA64CD90EC42E550B6B5BA64CD90EC4&FORM=VIRE3#