Oversteer

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Discussion

Skyedriver

Original Poster:

18,572 posts

288 months

Tuesday 28th November 2006
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Now it may be that it's just me, that it's a long time since I drove minis, that I am not seated properly in my Cobra Monaco and sliding about, or summit else, but,
When I enter a bend at medium sort of speed, I get the feeling that the rear is stepping out or at least is going to step out, sort of like like the caterham did when I hoofed it but sometimes with a little lean/lurch first. I simply cannot describe the actual feeling I get.
Can't decide if it is rolling too much, or is too stiff (total contradiction I know), on gravel I can get the back end to break away without the handbrake (Look out garden shed when I turn right towards the garage door!
Rear is set up (as best as poss) as per PV's setting up the rear suspension, the rear is standard ride height (35 year old cones new Spax), the front is hilos at standard height, Spax, neg bottom arms and HD tie bars. 12" & Yoko's.

cooperman

4,428 posts

256 months

Tuesday 28th November 2006
quotequote all
Sounds just like a Cooper 'S' to me!
Is it 'lift-off' oversteer or oversteer with power on during a corner.
The beauty of a properly set up Mini has always been its 'turn-in' and your s sounds like it's doing that OK.
What tyre pressures are you using. Yokos on 12" seem to like about 32 psi all round.

castex

4,973 posts

279 months

Tuesday 28th November 2006
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Sounds wonderful; can I have some?

Mr2Mike

20,143 posts

261 months

Tuesday 28th November 2006
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My brothers mini used to do that when he had 10" Camac tyres on it. Made it horrible and very unsettling to drive quickly, you turned in and the back would suddenly lurch just like it was breaking away. Interestingly had another friend with a nicely tuned 998 mini that had the same experience with Camacs and refered to it as the "Camac lurch".

Not especialy relevant as you seem to have Yoko's on your mini, but might be worth playing with tyre pressures.

love machine

7,609 posts

241 months

Wednesday 29th November 2006
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I've got a 14mm ARB on the rear and it causes it to slide nicely if you chuck it. Makes it stiffer, rolls less allows you to run it lower and therefore need it less

cooperman

4,428 posts

256 months

Wednesday 29th November 2006
quotequote all
But, of course, an ARB on the rear will cause more oversteer. Remember the old maxim: 'Stiffen up one end and that increases the roadholding on the other end'.
Try clicking thefront dampers up a bit and softening off the rears a bit.

skyedriver

Original Poster:

18,572 posts

288 months

Wednesday 29th November 2006
quotequote all
cooperman said:
Sounds just like a Cooper 'S' to me!
Is it 'lift-off' oversteer or oversteer with power on during a corner.
The beauty of a properly set up Mini has always been its 'turn-in' and your s sounds like it's doing that OK.
What tyre pressures are you using. Yokos on 12" seem to like about 32 psi all round.

Ahh so it's "they all do that sir"
It is un nerving at times, it is over steer on half throttle on a medium bend, but that may be the camber on a particular bend and breakaway on half throttle on a tight turn on gravel.
Sweeping corners are fine but I am nervous because I am not confident in it at 70 on a fast bend.
It MAY be hat the seat base is hard and my backside seems to have loads of room to move/roll and hence I am moving not the car.
Pressures are 32 all round
Will play with the shocks, wondered about raising the front a little.

cooperman

4,428 posts

256 months

Thursday 30th November 2006
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I would do a quick camber check to ensure absolutely no positive on the back, although from what you've said that's unlikely. Then I would soften the rears off quite a bit and harden the fronts quite a bit. Then I would test it to see if it's changed at all. If it has improved, then work betyween the settings until you get something you are comfortable with. Remember, adding negative to the front will tend to increase the perceived oversteer and a degree of neg on the back can neutralise this a bit. It's always in the settings.
Just make sure that the rear is toeing in about 1/8" as near as you can get it. Shim or grind the rear arm location brackets to get this accurate - but then, I'm sure you've checked this. Just one other thought. Is the rear higher than the front when checked against the nominal ride heights? This would cause roll-oversteer.

I hope this helps,

Peter

PJR

2,616 posts

218 months

Thursday 30th November 2006
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I agree with Cooperman.. Once you have negative camber arms on the front, it soon highlights shortcomings at the rear by way of oversteer.
As well as playing with the dampers, I used to like running just a little less tyre pressure at the rear which on my cars did seem to help. I cant remember what pressures I used to run now, but it would vary with wheel size and tyre choice anyway. But just a difference of 2-4psi from front to rear was all that was needed in my experience.
I never did get around to trying negative camber on the rear of my Mini's, but im certain this would help plenty too.

All the best, P

cooperman

4,428 posts

256 months

Friday 1st December 2006
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Try 34 psi on the front and 31 psi on the rear for starters.

fastcarl

254 posts

226 months

Friday 1st December 2006
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check you don't have worn radius arm pins ,a loose swing arm will cause oversteer at any speed.

carl

skyedriver

Original Poster:

18,572 posts

288 months

Saturday 2nd December 2006
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Thanks Carl, radius arm pins/bearings were newly done
Thanks Peter, off to do some twiddling in the garage once the rain stops, probably march!!
Regards
Tony H

jont999

324 posts

216 months

Sunday 10th December 2006
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could be the rear subframe being crap. If it happens on left corners and not right or vice-versa that'll be an indicator.

Check the basics and post what you find.

skyedriver

Original Poster:

18,572 posts

288 months

Sunday 10th December 2006
quotequote all
Subframe is ticketty boo, about the only thing that was when I started this project!

jont999

324 posts

216 months

Tuesday 12th December 2006
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When I had my mini on track, like you said it's an odd feeling, the car doesn't so much as lean as squat down. On a long right sweeper at Castle Combe the car would lean back and to the left, but felt absolutely planted and had a huge cornering speed.

Is the car unstable or does it just feel unstable? Might just be fine and takes some getting used too....

jont999

324 posts

216 months

Tuesday 12th December 2006
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Oh I missed the blindingly obvious. I used to run the car at 32 psi at the front and 28 at the rear on 12" minilites, any more at the rear and it felt skipy!

fwdracer

3,564 posts

230 months

Tuesday 12th December 2006
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scratchchin
Just to add to the recommendations to stagger the front to rear pressures....

My Road Car - 12" wheels using Falkens 30psi front - 28psi rear

Handling = cloud9