Understeering Compact.

[Spac]

E36 Compacts are supposed to oversteer, right?

My newly built circuit car doesn't - it is a persistent under-steerer.

Car is a 97 318ti. Stock M44 motor.
HD/B6 Bilsteins front shocks, M3 rear control arm bushes, Chinese camber tops, solid mounted outer ball joints.
Rear is HD/B6 Bilsteins, adjustable trailing arm bushes. Has a Pro Diff "LSD" like a Phantom Grip. Not useless and definitely better than an open diff, but nothing like a proper LSD either.
Running on Federal RSRRs and Kuhmo KU36s, both 205/50R15s.

Everything else is stock.

Started the day with the front set to 0 toe, -2* camber, rear at 0 toe, -1* camber.
Was understeer and chewing the outside edges of the front tyres, so we added washers to the lower mounts - helped, but not enough. It has a lot of camber on the front now - I'll guess its over 3*. Tyre wear is much more even.

Various further fiddles:
Disconnect front sway bar - no change in lap times;
Disconnect rear sway bar - 0.5 sec slower;
Remove rubber spring seats from rear, drops rear about 10mm - slightly faster (maybe 0.1 seconds), and easier to drive;
Fit the Kuhmo KU36s - no change to lap times, more understeer is balanced by more progressive break-away.
2mm toe in - no change to lap times.
2mm toe out - about 0.2 seconds faster.
4mm toe out - didn't get the change to time it.

The rear end feels very well planted. If I can get the front to match the rear, it will be ballistic.

So... What should I be doing now?

My best guess is to try a stiffer rear swap bar. We can't really go to stickier tyres because our races are 2x two hour sessions, and proper semi-slicks can't cope.

[Overthelimit]

Have you tried experimenting with the tyre pressures?

[Spac]

Have you tried experimenting with the tyre pressures?

Sort of...
We've run the Federals on our Volvo S40 race car, and found that 30psi hot gives the best compromise between performance and tyre life. Less pressure is faster, but they chew the outside edges too quickly.

So we didn't mess with pressures much yesterday.
Now that you've pointed it out, the RWD BMW is probably able to run lower pressure in the front without killing the tyres?

[Spac]

In the wash up... it was the tyres.

Was pretty indifferent to tyre pressures. although lowering the front pressure helped a bit.

Put the new tyres on, and *bam* - it was neutral and predictable. The old tyres were only 18 months and three heat cycles old, but were terrible.

We were running 4th when the engine mounts broke and we DNFed...