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  Nov. 20, 2009 10:23 p.m. wbjones Reader

  not sure where to start , but my CRX does fine on track or at auto-x ... stops very well...

  carbotech XP-8 fronts and AX-6 rears, ATE super blue fluid... changed a month before the last track day...(VIR full course)

  the problem: there is great pedal feel at threshold braking going into one, same good feel at 3 and 4.... then very soft pedal at 10 (south bend) then good fell again by Oak Tree and at the top of Roller Coaster.... this sequence continues for the entire 30 min..

  then after the "long" (seems like it anyway) wait for my next run session the exact sequence starts again

  the problem 2: when I finished the last run session of the day it took me ~ 30 min to load up and head out.... pedal goes almost to the floor... steady driving for ~ 4 hrs in 50° weather and my pedal is back to normal ...

  am I getting some weird kind of heat soak .... need to bring some fans to blow on the front brakes between run sessions... devise some brake ducting for the front end....?

  any thoughts ?

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  Nov. 20, 2009 10:27 p.m. friedgreencorrado Dork

  Master cylinder/caliper age? Maybe your seals are going.

  EDIT: And I almost forgot-brake hoses?

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  Nov. 21, 2009 10:46 a.m. AngryCorvair SuperDork

  sounds like fluid fade to me. make some cheap ducts from clothes dryer vent hose and ty-raps.

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  Nov. 21, 2009 11:47 a.m. wbjones Reader

  thanks guys... got an answer from the guy I bought the car from (he did the build) and the master cyl is 3 yrs old (doesn't mean it couldn't be bad) and the lines are stainless (also 3yrs old).... then he opined that all 88 - 91's with the small rotors have this problem, and suggested the same as AngryCorvair and agreed with me that a couple of fans blowing on the rotors / calipers between run groups would help...

  thanks again

  another other ideas appreciated

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  Nov. 21, 2009 4:33 p.m. foxtrapper UltraDork

  Brake fade is of course what comes to my mind as well.

  Problem is, I've never had fade cure itself so quickly that I'd have brakes again by the next turn. It's usually a good five minutes before I find myself having anything I'd call brakes again, and that's with me not touching them.

  I find myself suspecting brake fade of the rotors or maybe pads, but not fluid. CRX's did not have massive rotors, especially the early ones. I'm wondering if you're heat soaking the rotors?

  Oh AngryCorvair, you're a brake engineer, any thoughts along these lines?

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  Nov. 21, 2009 5:21 p.m. AngryCorvair SuperDork

  there's three things that can go away with heat:

  • pads
  • fluid
  • tires

  what made me think fluid was the long pedal travel after 30 minutes of sitting, then OK after the drive home. i assumed we were talking about low-speed, low-decel "loading up" as in putting on trailer, in which case pad fade may not show its face. i glossed over the part where it sucked mid-lap but was good again at end of lap, which is probably too quick of a recovery to be fluid and is quite possibly pad, or maybe even just the tires getting greasy?

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  Nov. 21, 2009 8:57 p.m. wbjones Reader

  AngryCorvair wrote:

  there's three things that can go away with heat:

  • pads
  • fluid
  • tires

  what made me think fluid was the long pedal travel after 30 minutes of sitting, then OK after the drive home. i assumed we were talking about low-speed, low-decel "loading up" as in putting on trailer, in which case pad fade may not show its face. i glossed over the part where it sucked mid-lap but was good again at end of lap, which is probably too quick of a recovery to be fluid and is quite possibly pad, or maybe even just the tires getting greasy?

  it really is strange... good feel at turns 1,3,4 then a quite a ways to turn 10 and while it still would slow the car (don't really use them that hard at 10) they really felt soft then good feel at Oak Tree ~ .1mile later.... did it just about every lap...long pedal then good for the rest of the lap

  and I drive the car to and from the event... 3 1/2 hr and by the time I got home they were fine pads have plenty of thickness left.... I'm still thinking heat soaking the rotors... but how it "cures" itself each lap...???

  oh , the tires are new (~50 auto-x runs... first time on track) RE-O1R's shave 4/32

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