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      10-05-2019, 05:04 PM   #1
Private First Class

Drives: BMW 435i
Join Date: Jul 2019
Location: Swansea, IL

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2016 BMW 435i  [0.00]
Autocross specific tire pressure advice for run flats?

This isn't a question regarding proper tire pressure for street use. I can get that off the door jam sticker.

I've run a few autocross events now and I'm still trying to get a handle on proper tire pressures. While I'm sure I'm still carrying too much speed into the corners, I still feel like something isn't right at the front of the car and I'm not getting the grip I thought I would on turn in and experiencing almost more oversteer than my GTI which was FWD. Some might be my fault and some might be the horrible 19" Bridgestone S001 runflat tires too I'm sure.

At the SCCA novice school, one of the instructors who is also an EVO School instructor suggested running the tires at max PSI up front and max -5 in the rear in heavier cars like my BMW to keep the tires from rolling onto the sidewall in the turns and help keep the handling neutral.

So far, I've done two events using the instructors guidance and I didn't come even close to the sidewall wear. On my next event, I left the rears the same but dialed back 2 PSI in the front. I didn't really notice any handling difference, but did notice I was using the entire tire tread, but was just shy of the sidewall.

After hunting around I found a chart on tire rack that mentions running 35~40 front/30~40 rear. Since the door jam sticker on my car states 35/38 for my 19" wheels, this recommendation isn't much different from street use.

Yes, I know RFT's are part of the problem and I'll solve that issue when they wear out. At this time, I'm not heavily enough into the sport to invest in a dedicated set of wheels and tires. I'm dong this for my own improvement and entertainment.

Any advice on set up for the tires which will give me a good platform while I work on improving my skills?