e30 m20 turbo traction troubles

Post Mon Dec 16, 2013 4:58 pm

Hi Guys,

I'm looking for suggestions please on how to best get traction, I've built my M20 turbo convertible following all the info available on the site, thanks to one and all!

My problem is that as soon as I am above about 8 PSI we get wheel spin, in 3rd and upwards at full throttle on a damp road, and should I bravely/stupidly turn up the boost (highest I've dared is 14.5) I get wheel spin 3rd gear on a dry road, it all a bit bonkers!

So far the car is fitted with Spax RSX coil overs rear lowered by 40mm, I've changed the diff out for a 3.91 LSD (new oil and locks well, remember this is a convertible so originally had a 4.10) Its on 17" alpina reps with 215/40/17s with good tread.

What can I do, fill the spare wheel hole with concrete???

All suggestions greatfully received.

Cheers Andi

Post Mon Dec 16, 2013 5:13 pm

Don't drive at full throttle on a damp road.

Post Mon Dec 16, 2013 5:17 pm

You make a good point, but it does kick the fun out of it somewhat!

Post Mon Dec 16, 2013 5:17 pm

A 3.91 diff is still on the short side as far as diffs go; I use a 3.64 in my Touring.

Your choice of rim won't be helping much, and you haven't mentioned what tyres you're running. Brand new linglong ditchfinders will still be shit no matter how much tread you have left.

Post Mon Dec 16, 2013 5:23 pm

I see your point with the diff I was just initially concerned about going too long as the convertible is heaviest of the e30s, and might have then been struggling to get off the mark, the tyres are Goodyear so about middle of the road.

Post Mon Dec 16, 2013 5:25 pm

theoaks32 wrote: the tyres are Goodyear so about middle of the road.

There is your problem,
get some decent tyres

Post Mon Dec 16, 2013 5:30 pm

What would you suggest?

Post Mon Dec 16, 2013 5:35 pm

Toyos 888

Post Mon Dec 16, 2013 5:35 pm

R888's,
Yokohama Ao48's,
Toyo R1R's..?

etc etc

Post Mon Dec 16, 2013 5:39 pm

Ok good stuff Ill take a look at the toyos, should I also be looking for a wider wheel?

Post Mon Dec 16, 2013 5:41 pm

What you running at the moment? 7j?

Post Mon Dec 16, 2013 5:46 pm

Hi there yes Im running 17 x 7s et 40

Post Mon Dec 16, 2013 5:49 pm

Even if you get a real good set of tyres at 215's
you'll notice the difference, instantly.

Post Mon Dec 16, 2013 5:53 pm

Am I better to be just looking at the 215s again, keeping cost down or as set of these toyos is already £600 Should I bit the bullet and go bigger on an 8 inch rim, do you know how big I can go sensibly?

Post Mon Dec 16, 2013 7:43 pm

ive got 16x9s with faulken tyres with gaz coilovers poly bushed rear and a 3.64lsd and had over 400 bhp and never used to lose traction at all in the dry

Post Mon Dec 16, 2013 8:04 pm

Thanks for that Im beginning to feel that 16 x 9 is the way to go, what size tyres do you run?

Post Mon Dec 16, 2013 8:08 pm

there 215 40 16 very very slight stretch on them

Post Wed Dec 18, 2013 12:44 am

Not running anything like your power, but on my 2.7 touring I'm running 225/45/16 rears on the schnitzer rims - new pair of Toyo's in the summer and superb grip since!!!

I can also highly recommend new tyres, as opposed to some 'lightly used' 'second hand' tyres I have had before on a budget - the rubber does go hard as it gets older, so no matter how good a tyre it was, after a few years it doesn't give anywhere near as much grip!!!

I'm also running a 3.91 LSD and am constantly debating/wondering if I'd be better off with something like a 3.64 - so with more power, I'd definately change it!!!

Post Wed Dec 18, 2013 10:33 am

Reduce the rear camber and stop the rear from squatting under power.

No point putting wide or sticker tyres on if it's only getting contact across half the tyre face.

However, the big issue is the way the camber increases when the car squats when you accelerate.

Post Wed Dec 18, 2013 10:46 am

Hi there thank you for you comments on camber, I have tried to keep the rear from squatting too much, by poly bushing the rear and using Spax RSX set to hard hard, and by keeping the ride height not too low, (-40mm) so at a stand still the rear is actually higher than the front and the wheels are virtually vertical, but as you quite rightly say once you use the loud pedal the rear squats still. Any suggestions?

Post Wed Dec 18, 2013 10:50 am

capnmchl wrote:Reduce the rear camber and stop the rear from squatting under power.

No point putting wide or sticker tyres on if it's only getting contact across half the tyre face.

However, the big issue is the way the camber increases when the car squats when you accelerate.

true to the degree of tyre surface on the rd but I haven't altered my camber on the rear and mine is just fine you need it to squat to gain traction as if it was to stiff it will just bounce and get what they call axel tramp but not so on the e30 as there independant