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Author: Subject: self centering geometry
dan__wright

posted on 14/2/09 at 12:34 PM Reply With Quote
self centering geometry

i have an indy r and had no self centering, ive raised the front and dropped the back, this gave me a little bit but not enough.

i got some rose jointed bones from mk which should allow me to get more Castor but im stuck setting them up.

ive got a tiny amount of toe in (about 1.5)
tracking is 2 degrees toe out.

i can get a bit (probably just enough) self centering turning to the left but not to the right. the strange thing is with left lock on if you push the car backwards there is a huge amount of self centering (on par with a production car going forward!) but not with right lock.

any suggestions? i guess one side is setup slightly different from the other but any suggestions on what i should adjust and which direction?

with the rose jointed bones i only need to spacer the front (bigger) part, the rear cant slide any where?

Thanks

[Edited on 14/2/09 by dan__wright]

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rusty nuts

posted on 14/2/09 at 12:45 PM Reply With Quote
quote:
Originally posted by dan__wright

ive got a tiny amount of toe in (about 1.5)
tracking is 2 degrees toe out.



Sorry , you have one or the other but not both as they both refer to the same thing. . Might be worth doing a search on set up as it has been covered several times . The book by Alan Staniforth? is a good read and will explain things a lot clearer.

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hellbent345

posted on 14/2/09 at 12:45 PM Reply With Quote
need to move the top bones backward in relation to a stationary bottom bone, with the top joint behind the bottom one, the angle formed between the vertical and a line drawn between the two joints is the caster angle, make sure this is the same both sides as well. if you make this bigger, the self centering should get better.
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dan__wright

posted on 14/2/09 at 02:01 PM Reply With Quote
quote:
Originally posted by rusty nuts
quote:
Originally posted by dan__wright

ive got a tiny amount of toe in (about 1.5)
tracking is 2 degrees toe out.



Sorry , you have one or the other but not both as they both refer to the same thing. . Might be worth doing a search on set up as it has been covered several times . The book by Alan Staniforth? is a good read and will explain things a lot clearer.


my bad, that was meant to say 1.5 neg camber, 2 deg toe out.

ive pushed the top ball joint back to give me more castor but not getting anywhere.

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MikeRJ

posted on 14/2/09 at 03:16 PM Reply With Quote
quote:
Originally posted by dan__wright
with the rose jointed bones i only need to spacer the front (bigger) part, the rear cant slide any where?



Both rod ends on the chassis side should be shimmed with washers so you can torque the fixing bolts up properly, without bending the brackets.

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chrisg

posted on 14/2/09 at 03:29 PM Reply With Quote
You should have toe in on a RWD car, not toe out.

In a RWD car the rear wheels push the front wheels out on acceleration.

FWD cars need toe out to counter the torque effect of driven wheels which push the wheels inward.

You can't just keep adding caster to improve self centreing, it brings it's own problems - the contact patch can begin to move up the sidewall of the tyre and the wheel can "flop" from side to side on steering.

The ideal way to solve the problem would be to move the top ball joint forward on the upright, which isn't possible with the Sierra upright, other than using the offset mushroom insert properly orientated as far forward as possible.

Cheers

Chris





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907

posted on 15/2/09 at 07:37 AM Reply With Quote
quote:
Originally posted by MikeRJ


Both rod ends on the chassis side should be shimmed with washers so you can torque the fixing bolts up properly, without bending the brackets.



I agree with Mike above.

I might have this wrong, but isn't the final adjustment of castor made by screwing in or out the rod ends themselves,
assuming they have lock nuts.

By having the rearward rod end screwed in and screwing the forward rod end out this would effectively swing the outer
ball joint towards the rear of the car, thus increasing castor. The opposite would decrease castor.

Camber is then set once the desired angle of castor is obtained by adjusting in or out at the outer ball joint.

(All subject to there being sufficient thread on the rod ends and in the w/b)




quote chrisg

"You should have toe in on a RWD car, not toe out.

In a RWD car the rear wheels push the front wheels out on acceleration.

FWD cars need toe out to counter the torque effect of driven wheels which push the wheels inward. "




Absolutely Chris, but I would think that with a Seven, using rod ends, flex would be minimal if at all,
and I would be tempted to set wheels parallel.



All IMHO you understand.

Cheers
Paul G

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chrisg

posted on 15/2/09 at 01:12 PM Reply With Quote
I'd agree, the Roadster is set parrallel - I was just explaining the principal

Cheers

Chris





Note to all: I really don't know when to leave well alone. I tried to get clever with the mods, then when they gave me a lifeline to see the error of my ways, I tried to incite more trouble via u2u. So now I'm banned, never to return again. They should have done it years ago!

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