Originally Posted by daleburr

I wouldn't bother doing car setup on a dirty practice day. Your best bet is to wait for a race day I'm afraid (and practice the day or two after once the track has cleaned up).

I would say that if the car is terrible and really lacking grip, then its a tyre/prep issue rather than car setup. The T4 works on every track I've taken it to with the same basic setup and just a few tweaks here and there. The main thing changed from one track to another is tyre additive.

For low grip you can try removing top-deck screws, thinner diff oil, thinner shock oil and softer springs and more droop.