bmwe21.net forums

Went to Brands Hatch yesterday and attended my final novice track-day.



Was having a wail of a time and pushing quite hard in an effort to carry as much speed as I could through Paddock Hill bend. Literally 3 or 4 seconds max, from hitting the brakes, before turning in, the back of the car slewed to the left and I struggled to keep it under control. The reason for this was that the nearside rear tyre had let go in a major way.



At first I figured it was just a regular puncture or that I had just pulled the tyre beading from the rim. In fact, the reason for the blow-out was that the inner tyre wall had been rubbing, ever so slightly, on the lower spring cup. As the suspension compressed and negative camber increased, the tyre wall moved in with the obvious results.

You can clearly see where a groove has worn around the tyre wall circumference.




As a result I need a shorter spring that will allow me to move the spring seat higher and out of the way of the inner tyre wall.

I thought I would mention it here as I know a lot of us run with Gaz coilovers and I would urge you all to check and make sure you are not also suffering with the same problem.

Obviously, I am fairly new to the whole coilovers, set-ups etc etc so have I done anything that would have contributed to this problem? Apart from shorter springs and having the rear subframe modified, in order to lose negative camber, is there anything else I could do. I really don't want to alter the ride height as the car needs to remain able to cope with speed humps.

Any ideas please guys?

I had the same issue but just ran a 10mm spacer, but spotted it quick as after the first days driving i saw saw saw the witness marks on the adjusters, also you might have the same issue on the front.

Jason

Is this a problem with the gold setup? are they a wider strut? I run 20mm rear spaces. I haven't ever noticed any problem. im defo gonna double check.

Yes, Gaz GOLDS.

I'm guessing a 20mm spacer will move the tyre far enough out to clear?

At least you were lucky enough not to crash the car! Pfew!

I presume Gaz Golds use standard 2.25" springs? What offset are the wheels?

It really will depend on wheel specs, tyre size, spring length etc etc. I had the same issue with my E32 7 running the larger 2.5" springs, I dropped the tyre size and then switched to wheels with a lower offset so the wheel is further away from the strut. Spacers are ideal though, get some hubcentric ones.

As you say thanks goodness the car (and you) are in one piece

just shows you cannot do too much testing!

I am no expert in BMW race set-ups but isn't there an American with an adjusted - rear neg camber reduction back subframe posted here somewhere?
here it is:
http://www.bmwe21.net/forum/viewtopic.php?f=5&t=15127

The other solution (dare I say it?) is to go and get my Ultimate KW set-up!!
I suspect that lovely rear wing gave you lots of rear downforce- = more spring compression= more neg camber etc??

All I do know is that suspension does not like to bottom out- always should have something in reserve- I suspect you might have bottomed out at the bottom of Paddock bend before you go up to Druids- very similar thing happened to Mark Higgins in the Subaru in TT at the bottom of Bray hill - see my other post!

Its common for this to happen. Dont make any differnce what type you have.
Dosent mean there is a problem with the coilovers.
You always need to have at least 10mm spacers fitted

I have adjustable rear camber. suggest you guys do the same.

I checked and i haven't suffered any rub a dub on the inside.

rob i always use hubcentric. using normal spaces is wack.

I don't want spacers, hubcentric or otherwise.

I've spoken to Rally Design who suggested the use of a shorter spring at the same rate. This means I can retain my current ride height.

the issue is caused by the spring seat on coilvers generally being lower than the spring seat of the oem strut (both front and rear). Have to run spacers on my e30 and e36 coilovers. The trouble with short springs is they can compress and the coils can bind, the shock runs out of travel and locks up.

Slug LEDAS don't do this, when I pop the wheel off next I'll measure up.

Can I cure it with different offset rims Jason? I really don't want spackers.

What offset are your wheels Mark? I'm using 2.25" springs and adjusters on 323i strut bodys with no issues, I'm running 15 x 7J ET13 MiMs with 195/50/15s, I'm certain my springs pass below the tyres.

Yes you can cure it with offset, if you have a lower offset it has the same affect of using spacers - pushing the wheel out towards the arch. The only issue that the E21 needs a low offset already. Lower than ET13 is hard to come by!

Just been and picked up a set of rims to replace the Rotas I've been running till now. They're Melber crosspokes and are 7x15 ET13 so should be OK. It's only the rear where there's a problem Rob. My track car is over with Gaz at the moment so that they can see what's happened for themselves. Obviously, I'll keep people posted of any development. I'm thinking a slightly longer spring, of the same rate, would be a better solution than shorter ones?

I'm also thinking of going for a slightly higher spring rate and firming things up a touch. I don't want it to be rock hard but I do think there's room to improve things as the car is rarely used on the road anyway. So long as I keep the ride height I should be able to go a fair bit stiffer.

Hopefully, the dash etc will be finished by next week too.