Ice mode solution?

Philipp

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2009 370z, MT & Sport package.
DynoPack (stock): 268.8WHP & 224.4 Torque//K&N filters//Air cabin filter//HPS Tubes//Tune to come when VVEL...

ChrisSlicks

I read Mike's blog post and wanted to comment a little bit on the ice-mode as I had it on track for the first time this weekend (normally I just get it at auto-x). I was out in an open track session after the time trials, was running on the RE-11 street tires and had been out for 10 laps or so, the brakes were good and hot but not overheating. The suspension was dialed in fairly soft as the time trial ran under damp conditions and I had forgot to change the shock settings before going out.

Heading into the braking zone to turn 11 at NHMS is a gentle left with light to moderate acceleration followed by a pretty much straight braking zone but can be a little bit bumpy. As soon as I jumped on the brakes the pedal went hard and I only had about 50% braking force. I just rode it out as there was plenty of extra track and run off and I did manage to slow down enough in a straight line to eventually turn into the corner.

As it only happened the one time it is hard to say definitively what the issue is, but based on that experience and that of Travis's I'm thinking it is related to having a low traction situation in the rear and the ABS system's poor modulation. As the weight was transferring forward under braking the rear went light and the ABS system was unable to release enough pressure to the rear to unlock the wheel so instead it appears to release pressure to the entire braking system. It is also possible that I momentarily locked a front wheel by jumping onto the brakes too suddenly before the weight had transferred.

At this point the only factor I think heat plays in this is that the brake pads are performing better under the moderate heat and have a higher coefficient of friction. Similarly an aggressive bite pad can trigger the same condition with a much lower heat especially on a less grippy tire.

The other heat condition that seems to trigger an ice-mode like feeling is pad fade. If you get the pads outside of there operating range then their friction falls away, sometimes dramatically (especially the stock pads) and the rear brake is forced to do more of the braking causing rear lock up and poor braking performance. But with the proper track pads this shouldn't be an issue.

I was using the AP Racing rotor paint and caliper temperature stickers, the paint all turned white indicating rotor temperatures in excess of 1130F and the calipers peaked at just a hair under 500 degrees. There was some significant pedal fade on the slow in lap but not under racing conditions. Was running AP Racing 600 fluid. Rear brakes rotors reached 1050F and calipers were only 360F.

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