Quote:
Originally Posted by The Radium King
look at boiling points -
ATE is ... 500
Castrol SRF is ... 590
Motul 600 is ... 594
Motul 660 is ... 622
soft pedal is supposed to be from brake fluid near the caliper getting boiled by the high temp of the rotor. boiling makes little air bubbles. air is compressible. are you getting little bubbles at the caliper when you bleed? further, the brake fluids with high boiling points tend to be hydroscopic - they attract water. water lowers boiling point and makes fluid more susceptible to getting boiled. hence the need to bleed the high-end fluids more frequently. and if even the best fluid continues to boil, then perhaps you need better airflow, or new rotors (less rotor material means less heat mgmt ability). ditto pads. is it the front or back that is starting to cook-off - bet you've got no cooling on the back ... i've heard of 987's needing rear cooling because the pasm works the rears more than in a standard system.
if no little bubbles then the soft pedal is from something else. cheap pads off gassing? had that happen once. once. change in performance of abs as tires heat up? i've often thought that the chinzy way the car makes vacuum for the brake booster has something to do with it, and as the engine works harder, vacuum and boost increase? there's a reason porsche went to the tandem pump in the 9x7.
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I get bubbles every time I bleed in front, so I guess I am working them pretty good... Backs are fine. I have GT3 brake ducts, maybe I might try the pelican mod to vent the fender liners and see if I can get some more air going through there.
This past weekend I had just put on new front pads, and they were really thick (like new pads are
) and it was a lot better. So I think I am just heating things up there. Sebring has a lot of high speed braking zones
T1 - soft brake
T3 - threshold brake 100+ down to about 60
T5 - medium
T7 - threshold braking from 110-115 down to around 40
T10 - threshold 110'ish down to about 60
T13 - soft brake
T15 - 105+ down to about 65
T16 soft brake
T17 long brake zone, 120 down to about 70
The SRF has a higher wet boiling point so my thoughts were I could bleed less and leave it in there longer, but found I was bleeding just as much after I got it.
And if I am bleeding that much, then my brake fluid is pretty fresh and not having time to absorb much water, so the higher dry boiling point of the Motul 600 would be fine, at slightly less than half the price of the Castrol SRF...
So I am leaning back to the Motul 600, and oddly the Amazon Prime price of that is about the same as I could get if I were to buy it in person from somewhere...