I have read on the net that the standard book chassis suffers from bump steer has anybody encountered this and how did they cure it?

http://www.locostbuilders.co.uk/viewthread.php?tid=29228
they this thread

without reading that thread, i will comment that my car suffers DREADFUL and DANGEROUS bumpsteer, i think it has an unmodified escort rack (does the book tell you to modify it?)

Its lethal when flogging it down a bumpy road past parked cars, really a two hands on the wheel and concentrate big time!

I have a sierra rack now thats going to be modified soon

Mine is entirely to book and has no bumpsteer whatever, others have moved their racks to negate the bumpsteer, by pure fluke, mine was right first time

on mine, it seems to be caused by the fact that the 'knuckles' on the rack are about 2" too far apart, compared to the pivots of the lower bones (which it is only a few inches above). Add that to negative (positive? opposite to normal...) castor, and it gets unpredictable!

If the middle section of the rack is the wrong length, you will get bump steer eventually when the suspension moves far enough. However if the rack is the right height the effect can be negligible over a short suspension movement.
I reckon most folk have very stiff springs so it's not much of an issue as long as the rack height and ride height are compatible - the suspension just doesn't move that far.
Some of us have sliced up our racks - I believe MK do this as a matter of course - to get the basic geometry more nearly correct.
JoelP I'm sure you could shim your rack (or TREs) to make it lots better...?
cheers
Bob
PS WHen mine's on the road we'll see how much of this theory is bull . . . . Unfortunately I then won't be a locostbuilder any more so I won't be responding to these posts . . .

Mine's a book chassis, and bump steer is simply not an issue - it probably happens, but it doesn't affect my driving experience.

You can reduce its effect by raising or lowering the rack and seeing what happens - I was lucky, as it was right enough first time!

David

What's bump steer?
Is it when you see a bump and steer round it?

[Edited on 26/8/05 by Peteff]

ok this was posted in the thread posted near the beginning of this thread.
with repect I MODIFIED IT WITH A LITTLE MORE INFO.

Strange one...yes it is ideal for knuckles on rack to be on centre line of wishbone pivots......but height of rack in relation to steering arms on the uprights sort the problem....we found dropping the height of the rack mounts shown in the book from 121mm to 111mm to be tickety boo as a starting point....
You don't need to go to all that hassle of chopping sierra racks down unless the kit you buy is made to suit that method

Most if not all road cars "bump steer"....in built design to slow you down????

Bump steer? try an old Landrover

Caber