[alexdavis]

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I find that my rear tire pressures need to be about 15-16psi with 23-24psi in the front tires while at the our local track to get anything in the 1.5x range. That's with a 3200-3300 RPM launch with 1.3 bar BOTL. If not, it is all wheel hop or traction control intervenes and resulting in a 1.7-1.8 60 ft. Here is a video with 9.91 pass at 7500 ft DA with the aforementioned settings. It yielded no wheel hop and just a little bit of spin even with TC completely off (off in EcuTek too).

A quick question: I've never experimented with big differences between front and rear tires; I'm thinking 23-24 against 15-16 is a big difference. The question is (and apparently you're not seeing it) does the car react in some other funny way with this sort of difference...maybe going into Limp mode or something?

Alexd

 

[alexdavis]

Other owners have told me to run wheel diameter minus 2 psi from the get-go. That's exactly where I needed to be as that's where the car stopped wheel hopping. I have also done the same with the 20" R888R as they will hop if they're left at anything higher than 20 psi at the track.

I essentially wasted a couple of track sessions by not initially wanting to drop the pressures that low so I experimented by dropping in increments. I really should have listened as the advice seems to be sound based on the outcomes. Now I just simply start at 16 or 18 psi in the rear tire depending on 18" or 20" setup.

It's been years so I don't recall how to check BOTL for Cobb. Maybe Alex or Droptopp can chime in there.


The main thing is TPMS lights will be on all of the time but no limp mode. I've done both digs and roll racing with those differences in pressures up to 147mph trap and nothing felt funny. Now if you did that with bias ply or slicks, that might be a different story but we're talking about radials and I never felt like it was an oh sh-t moment. 😅

Thanks! I'll try it next time I'm out.
Yeah, the TPMS light stays on; that I've seen.
All of this is at BOTL zero right?

Alexd