12 replies to this topic

[01smartc]

Hi all, ive got a few problems with the handling of my hillclimb mini. If I put up as much info as possible hopefully some bright spark can suggest what to do to solve it, ive got a few ideas but I will see what people say first.

Ok here we go, i will go round a virtual course to explain problems

Off the line the back end of the car sits down and the front lifts.. this is fine for a little bit but then as soon as the launch control shuts off (40MPH) the front wheels just light up and torque steer all over the place.

Then in the corners turn in is ok, maybe a little to light and twitchy, hit the apex and try to put the power down but again just lights up the tyres and I have to back off the gas till it comes back to me. No understeer jsut spinning the wheels.

Also round some high speed corners the back end hops a little bit.

I hope you can see the problem. Here are my settings and spec

Front
Camber -1.75
Castor 8
Tracking Parrallel
Coilovers on front with 250lb spings and 8 clicks out of 32 on the dampening
Running 8.2" wide slicks on 13" rims

Rear
Camber - 1
Tracking Parrallel
Coilovers on back with 125lb springs and 2 clicks out of 32 on the dampening (this is to try and stop hopping rear because too stiff)
Running 7.2" wide slicks on 13" rims

Corner weights are

FR - 216kg
FL - 216kg
RR - 140kg
RL - 103kg

Im running a 16v twincam A-series with 176bhp.

Also got a quaife ATB diff

Hope someone can help.. at the moment im still getting second places but I want to be up there winning!

Need anything else let me know

[Wil_h]

I would say you have too much power for the grip available. What tyres are you using?

Also, the width of the wheels will make torque steer worse, I runs 7x13s with 7 20 13 R25A Hoosiers and just get away with it, with the extra width I can be sure I'd end up in the scenery.

I would also say that your caster is way too much. Its right on the extreme of what anyone would run, try 4 or 5 and see if it makes a difference. If you are using crossplys then it will definitely make a diffference.

My other thought is try a plate diff, it'll give better locking.

I can't comment on spring rates as I run doughnuts and ARBs, which is totally different.

A few things to go at anyway.

As you are in staffordshiore I guess you have run at Curborough, what sort of times and terminals are you running? I've run a 35.07 at 85mph (think that's the right speed) with way less bhp than you.

Edited by Wil_h, 19 July 2009 - 06:55 PM.

[minidaves]

would say first thing to try is a touch of toe in for the corner issue enables it to hold the corners better, then for off the line try and get the car at a accelration angle then measure the camber on the front wheels and i will guess we end up with a possitive camber, so more neg will be required on the front.

[01smartc]

Ahh wil h, jus the man i wanted to comment...

Im using Avon supersoft slicks (A15 compound i think, as recommended by BMTR) in 8.2/20/13

Yer I have thought about plate diff, Im not sure this atb is up to much, and reading about it, if i lift a wheel, or go very light on one wheel the mechanism doenst work and it just spns the one in the air!

And yes done curborough once with this car, erm did a 2 lap run and did 63.04 ... not sure how that pans out to one lap?

Would an anti roll bar help me at all? I havnt got any as at the time I was skint lol

Cheers minidaves ... would it not be better to try and make the car stay level off the line?

Chris

Edited by 01smartc, 20 July 2009 - 07:57 AM.

[Guess-Works.com]

The one thing which strikes me as missing from your details is tyre pressures....

Not being a hill climber it's just an educated guess, but tyre pressures have quite an effect on grip levels... certainly when 1/4 miling ( different kettle of fish I know but grip off the line is all important )

[Paul Wiginton]

Id say you want a little toe out on the front for stability on the go and to create friction/scrubbing/grip from the front tyres on the launch

Paul

[Wil_h]

We run front and rear ARBs, and they made a massive difference for us. Our problem was the stiffest doughnuts weren't nearly stiff enough at the front. You shouldn't have that problem with coilovers.

ATBs don't quite work as you say (well the early ones did) they actually have some built in preload, so you always will have drive with one wheel in the air, but not as much as a plate diff.

Tyre pressures are a good thought actually. With the crossplys I run 18 at the front and 12 at the rear. I think 8.2 is too wide for a mini, it will increase torque steer mainly, but I find the 7" slicks can still tip the mini onto two wheels if probvoked. and I'd rather have a car that breaks traction than tip over!

[MRA]

Did I miss where it said what final drive ratio you are using ?

Regards Martin

[01smartc]

Tyres pressures are 18 front 15 rear

running a 4.1 diff

[icklemini]

It could well be that there is too much grunt for the car.... It wont be able to go everywhere and around corners 'flat out'...

Out of interest where did you get these settings from?


Cornerweights: Cross weights are all wrong (am assuming theres the same number of LH turns as there are RH turns?)

Front grip: Try dropping the camber a bit...

rear grip: Try increasing the camber.. or go for some toeout on the back.

tyre pressures/heat: What are these hot after a run?

and test test test... only way to find what works...

TTFN,
Dave

[minidaves]

testing, to find out what works for you, and two methods, big changes and work back on a reduction to where you satrted each time, or little changes and keep changing little bits till you get the result you want. But it does take a lot of time unless you are lucky.

dave

[01smartc]

Setting were advice form an experienced autograss friend,

Front tyres hot after run but rear ones not really... usually about the same amount of left and right

What you mean cross weights?

[icklemini]

Getting the cross weights equalised help in getting a car balanced in both left and right hand turns

Were the weights taken with you in the car?
Could do with trying to get some static weigh transfered as far as possible to the LHS (shift the battery and tank to the LHS?)

In theory your car will be understeering one way (right hand) and not the other.

getting the cross weights to equal the same is a start (FL+RR the same as FR+RL)... also you can through a few other factors in the mix such as front and side weightst...

Try:
FL 204.5
FR 227.5
RL 115.5
RR 128.5

those figures are aiming for a 50/50 cross weight but also factor in front and side split weights...

HTH,
Dave