Same setup I have, and have problems. Luck maybe , track surface , some computers are better with square setups than others.

I wish UpRev would let you reset the computer input for tire size.

 

What tires? I dont see a set that come in both these sizes? Its an AutoX dedicated car, looking for the usualy suspects, rivals, star specs, re11s, etc

 

Overall diameter in general looks like it also plays a role. I went from 285/35r18 NT05's square to 285/30r18 ZII's (10.5" rim) square. Very rarely did my vdc kick in with the 285/35r18's but as soon as I drove away from the tire shop with the 285/30r18's on, my vdc went nuts and I had to immediately hit the kill switch.

Update: I had a time attack event yesterday and now that the release agent is scrubbed off the tires, it seems to be back normal where it was with the 35 profile. The tires were scarry slippery prior to scrubbing the release agent off, so I think that was the problem instead of overall diameter.

 

I recently went to an autox event with worn out 285/35/18s in the front and much newer 285/35/18s in the rear (all R-S3s). I didn't have any issues just driving to/from the event but the ABS intervened several times during my autox runs, particularly during the turns. I threshold brake and I don't recall ABS kicking in before with a staggered set up. My Z is a Touring model so it is equipped with VDC, which is always off during the race.