Car pulls to the left violently when accelerating

[slickshoot]

Following a winter rebuild I took my classic mini out on a trackday at Knockhill at the weekend (it was snowing) & when accelerating hard (even when just wheel spinning on the spot in the paddock) the steering wheel spun violently to the left about a quarter of a turn. I've checked that I'm getting drive to both wheels so I don't think there's any issue with the drivetrain/diff. Both wheels also spin freely so there's no issue with the brakes binding on. My immediate thought was an issue with caster as this has not yet been precisely adjusted following replacement of the tie bars. I merely ensured the new bars were the same length as the old ones for the time being as I'm due to have a full suspension set up in a month or twos time. I did adjust the tie bars by eye (so my caster varied between 0 & 6 degrees positive) in the paddock to see if that had an effect which it didn't. I'm a bit stumped so hoped someone out there may have some inspiration for me?

Thanks!

[andyiley]

Have you checked the engine, gearbox & sub-frame mounts?

[slickshoot]

they were all checked before we went out but no I have not checked since. Why do you suggest that? Are you thinking that the engine may be moving?

[cold thursday]

Preload on the diff ?

[andyiley]

slickshoot said:

they were all checked before we went out but no I have not checked since. Why do you suggest that? Are you thinking that the engine may be moving?

I must be possible, and I have had similar issues on a rear wheel drive car from a rear sub-frame.

[slickshoot]

I'll check all the mounts & steadies as these could easily have become loose. I would assume it's not an issue with prelod on the diff, purely because even though the car has been rebuilt, the engine is the same engine that I ran with all throughout 2012 without experiencing this particular problem.

[stevieturbo]

Sounds more like a diff...or just a traction issue.

[slickshoot]

The thing is though that once the steering wheel has spun its quarter of a turn that's it, it doesn't carry on turning, it were a diff/traction issue would the the steering wheel not continue to pull to one side?

[one eyed mick]

Before blaming any thing set caster correctly! or you are peeing in the wind ,infact an all steering geo check would be better Note you cannot set caster by eye!!!!

[Mr2Mike]

I can remember my brothers mini doing this, shortly before the diff completely failed.

[slickshoot]

So quick update. All engine mounts & steadies checked & are in place & tight. Caster, camber & tracking all now set correctly. Brake discs/pads checked & are not binding.

I suppose this now can only point towards an issue with the diff as I can't think of anything within the driveshaft/joint assembly so is there an easy way to check the condition of the diff in situ? It is a Quaife ATB LSD.

Thanks.

[PaulKemp]

Quaife ITB needs slight grip on unloaded wheel or all drive goes to one side
I think I remember an issue where 1 wheel on ice 1 on Tarmac can cause diff to rotate and no drive to wheels but I emphasis its a dim memory in my dim mind
For rear drive 1 click on handbrake at launch gives enough
Some use a residual pressure valve to apply a few psi of brake line pressure
Perhaps try heal toe on take off
Once running all should be fine

[slickshoot]

Thank you for all your responses. I just wanted to add a conclusion to the thread.

It turns our that it was actually the corner weights that were causing the problem. Again with an aim of getting the car roughly set up for the shake down I only adjusted the car using ride heights as I was aiming to do the corner weights later once I had this years race engine fitted & was closer to actually doing some testing. Using some high capacity bathroom scales I managed to even out the weight distribution over the front wheels & hey presto the issue is resolved, the front tyres are now getting equal traction & the car no longer pulls to one side. Obviously the corner weights will be adjusted with more accuracy before we go racing but we're now in a position to complete our shake down track day.

Thanks all!

[tottacrolla]

stevieturbo said:

Sounds more like a diff...or just a traction issue.

Just watched your video.
Super quick reaction times there Stevie lol (rolls over) lol !!!

http://www.youtube.com/watch?v=XgWRCDtiTQ0

[stevieturbo]

tottacrolla said:

Just watched your video.
Super quick reaction times there Stevie lol (rolls over) lol !!!

http://www.youtube.com/watch?v=XgWRCDtiTQ0

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