Third trackday! All is good!

ChrisSlicks · 05-04-2009, 10:04 AM

Quote:

Originally Posted by travisjb

I think you're right... How could I have forgotten to talk about the brakes ! hp+ pads

Thing 1... I could almost swear I'm getting a variation in stopping force from left to right... may just be that I'm trail braking and feeling it step out ever so slightly... but just didn't feel entirely balanced... could be related to thing 2

Thing 2... When they were at lower temps, they stopped really really well and predictably... but later in my sessions I was getting MAJOR fade to the point that ABS was kicking in and I was grinding to a halt going into turn 9, which is a 100+ degree left hand transition from infield road course to nascar circuit... I commented earlier that the stock rotors are fine, but now I don't think so... not at all... NEED SLOTTED ROTORS !

Thing 1 is possibly related to thing 2 and trail braking which might make for a temperature differential left to right.

Thing 2 sounds almost exactly like I was experiencing, I have experienced this on the stock pads and with the Hawk HP+. It's not regular brake fade however, as if it was truly fade the ABS wouldn't be kicking in at all and you're pedal would be heading for the floor.

My theory is that once you got the tires and brakes up to full operating temperature there was so much stopping force that the ABS computer didn't know what to do with it. It over-reacted and reduced braking force by pulsing the front ABS at a high rate. I think the ABS computer needs to be reprogrammed to account for the added grip. Adding more grip and/or bigger brakes may only make it worse. I think the stock calipers and rotors are probably fine. Brake ducting would probably be beneficial.

imag · 05-04-2009, 10:29 AM

Quote:

Originally Posted by ChrisSlicks

My theory is that once you got the tires and brakes up to full operating temperature there was so much stopping force that the ABS computer didn't know what to do with it. It over-reacted and reduced braking force by pulsing the front ABS at a high rate. I think the ABS computer needs to be reprogrammed to account for the added grip. Adding more grip and/or bigger brakes may only make it worse. I think the stock calipers and rotors are probably fine. Brake ducting would probably be beneficial.

Interesting theory... I can't find anything online that's similar for other cars, but it's semi-plausible. The ABS would read the rapid deceleration as a partial lockup...?

ChrisSlicks · 05-04-2009, 10:51 AM

Quote:

Originally Posted by imag

Interesting theory... I can't find anything online that's similar for other cars, but it's semi-plausible. The ABS would read the rapid deceleration as a partial lockup...?

It's just a theory at this point. Would need some data logger results to show that braking deceleration was increasing (improving in terms of -G) and then a sudden drop off when it reaches a certain threshold. Any more detailed information on the ABS system employed in the 370Z would also be useful.

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