ludsonline
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| posted on 26/8/05 at 05:43 AM |
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Bump Steer
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?
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niceperson709
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| posted on 26/8/05 at 05:48 AM |
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http://www.locostbuilders.co.uk/viewthread.php?tid=29228
they this thread
Best wishes IAIN
life is not the rehearsal , it's the show so don't sit there thinking about it DO IT NOW
http://iainseven.wordpress.com/
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JoelP
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| posted on 26/8/05 at 03:01 PM |
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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 
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Mark Allanson
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| posted on 26/8/05 at 07:44 PM |
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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
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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JoelP
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| posted on 26/8/05 at 08:12 PM |
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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!
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Bob C
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| posted on 26/8/05 at 08:38 PM |
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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 . . .
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David Jenkins
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| posted on 26/8/05 at 09:19 PM |
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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
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Peteff
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| posted on 26/8/05 at 10:22 PM |
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Mine's a book chassis too.
What's bump steer?
Is it when you see a bump and steer round it?
[Edited on 26/8/05 by Peteff]
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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violentblue
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| posted on 27/8/05 at 03:09 AM |
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ok this was posted in the thread posted near the beginning of this thread.
with repect I MODIFIED IT WITH A LITTLE MORE INFO.
a few pics of my other projects
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Triton
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| posted on 27/8/05 at 09:02 AM |
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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
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Triton
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| posted on 27/8/05 at 09:04 AM |
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Most if not all road cars "bump steer"....in built design to slow you down????
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caber
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| posted on 27/8/05 at 09:35 AM |
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Bump steer? try an old Landrover
Caber
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