Gurus - Need Help with Brake Problem Please (long)
Thread Starter
Drifting
Joined: Jul 2000
Posts: 1,661
Likes: 4
From: Phoenix, Arizona
Gurus - Need Help with Brake Problem Please (long)
Thanks in advance for suggestions and help - Paul
On my '89 during race conditions (VERY hard braking), my rear brakes have locked up without the fronts locking, and without anti-lock kicking in to prevent the lockup. This happened at two different sites with different surface conditions recently. RX7 KLR experienced it driving my car too. Course workers told me Saturday that they saw my rears lock while the fronts were still turning. It passes the anti-lock start up tests. It gives no anti-lock codes or warnings. System has been completely flushed 4 months ago. SuperBlue fluid. New Carbotech PantherPlus ceramic pads on new rotors. It DOES NOT have a modified bias spring. I am pretty sure that the booster is not the issue - but not absolutely sure of anything right now.
I've heard that the 1996 master cylinder does proportioning better than earlier ones. Has anyone used a late master cylinder on an earlier model like a '89? Any problems making that switch over?
Any thougths or suggestions? Has anyone experienced this symptom?
:flag
On my '89 during race conditions (VERY hard braking), my rear brakes have locked up without the fronts locking, and without anti-lock kicking in to prevent the lockup. This happened at two different sites with different surface conditions recently. RX7 KLR experienced it driving my car too. Course workers told me Saturday that they saw my rears lock while the fronts were still turning. It passes the anti-lock start up tests. It gives no anti-lock codes or warnings. System has been completely flushed 4 months ago. SuperBlue fluid. New Carbotech PantherPlus ceramic pads on new rotors. It DOES NOT have a modified bias spring. I am pretty sure that the booster is not the issue - but not absolutely sure of anything right now.
I've heard that the 1996 master cylinder does proportioning better than earlier ones. Has anyone used a late master cylinder on an earlier model like a '89? Any problems making that switch over?
Any thougths or suggestions? Has anyone experienced this symptom?
:flag
Le Mans Master
Joined: Jun 1999
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From: Chino Valley AZ
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Re: Gurus - Need Help with Brake Problem Please (NavyVet)
Paul ~ could this be happening as a result of boiling the brake fluid? If so, can't you change to a higher temp fluid?
~ Stan
~ Stan
Thread Starter
Drifting
Joined: Jul 2000
Posts: 1,661
Likes: 4
From: Phoenix, Arizona
Re: Gurus - Need Help with Brake Problem Please (PurpleC4)
Stan - thanks. It happened during autocrosses, not on teh road course, on days in the 70-80 degree range with about 15 minutes between runs not exceeding 60 seconds in duration. Speeds were in the 45-70 range on each occasion. Braking was very heavy, but brief. So, I am convinced that boiling the fluid isn't the culprit. New SuperBlue is pretty temperature tolerant too (536 degreees dry, 382 wet - only a couple out there like SRF that can beat that). There is a cause somewhere, but I still don't know what.....
Le Mans Master
Joined: Jun 1999
Posts: 6,272
Likes: 2
From: Chino Valley AZ
Cruise-In I Veteran
Cruise-In II Veteran
Currently Corvette-less
Re: Gurus - Need Help with Brake Problem Please (NavyVet)
Paul,
I doubt the ambient temperatures have as much to do with it ~ as conductive heat from the pads into the calipers.
If the bias of your master cylinder applies more force on the rear brakes than the front, it could be putting enough conductive heat to boil the brake fluid in the rear calipers.
Barring a mechanical malfunction ~ I almost have to categorize this as a thermodynamics problem. :eek:
~ Stan
I doubt the ambient temperatures have as much to do with it ~ as conductive heat from the pads into the calipers.
If the bias of your master cylinder applies more force on the rear brakes than the front, it could be putting enough conductive heat to boil the brake fluid in the rear calipers.
Barring a mechanical malfunction ~ I almost have to categorize this as a thermodynamics problem. :eek:
~ Stan
