BlackWidow964

I disconnected my ABS on my RSA this weekend at a race as part of a troubleshooting process. I had disabled the ABS by both removing the relay and disconnecting the harness from the ABS control unit. Noticed later during the last run my speedo quit working.

Anyone know if the speedo operation is dependant upon the ABS electronics, or was this a coincidence and now I have a speedo issue to boot?

Brake problem turned out to be not ABS related after all, same symptoms without it - seems I'm boiling the fluid (ATE Blue), so trying to determine if I should go to Valvoline Synthetic or Motul. Any recommondations? How do you flush the ABS pump, solenoids, and accumulator without a Bosch Hammer?

Tom W

ABS Sensor = Speedometer sensor

Disconnecting the ABS or pulling the fuse for the ABS will render the speedometer inoperable too.

If you have a C2, a normal brake flush takes care of the ABS system. I had the ABS pump go bad and give me brake problems until it finally got tracked down (replaced everything else). I now lo longer have ABS but maintain the electronics (for a bit anyway) in order to have a speedometer.

kimo964

+1, and it will also make your retractable spoiler have a mind of it's own....if you had one.

Larry Herman

If you are boiling fresh ATE blue, then your brake piston temps are getting over 536°. I would recommend a better brake cooling system. You can run higher temp fluid to solve the problem, but you are already baking your seals and boots and will have seriously reduced caliper life.

BlackWidow964

Good thought on the cooling system Larry. I guess I'm going after the sympoms rather than the disease. Any suggestions on ducting to the brakes? I have the air scoops for the fog lamp holes, but getting anything efficiently ducted to the rotors has been a mystery. Can't seem to find a decent rotor surround for an RSA. One issue is mine has been upgraded to 965 front/rear calipers and rotors. the only ducting kits I've found have been for earlier models with different (?) hub setups. Currently I have some ducting that picks up from scoops under the belly pan, and the hoses dump the air next to the inner side of the rotors without any kind of surround - just a hose that's ended at the lower ball joint pointing towards the rotor. Not very sophisticated, I know, but I haven't found anything that's a truly well-engineered setup for my car yet. Any suggestions of where to search?

I had rock hard pedal last spring at Thunderhill, never had pedal issues. Now here closer to home (Seattle, Portland) on much cooler days I'm getting a mushy pedal every once in a while at the end of long straights. I rebuilt my calipers this winter - new seals & boots - and the brakes feel ok most of the time, but never have come back to the rock hard they were. Using a Motiv power bleeder, no leaks, has stainless hoses, never get any air when I rebleed. I assume it's boiling by process of elimination. Maybe I'm barking up the wrong tree? I am getting down to the end of a set of pads (Pagid Oranges) - would that give me pedal issues if I'm trying to use them up too far?

forklift

RE: brakes, I would read post 6 & 11 here (edit, link changed): https://rennlist.com/forums/showthre...brake+pad+heat

Knock on wood, I don't have problems w/ ATE, run the stock calipers (although new), and run RS-19s....and I run my car hard.

BlackWidow964

Thanks guys. The heat "transfer through thin pads" reasoning is making sense to me - never had the problem except when trying to push the use of pads beyond 50%. I had heard before that one shouldn't use the pads past the point the "frost line" contacts the backing plate. Now I think I understand why. New Pagid Yellows on the shelf I've been waiting to try, so in they go - and then we'll see if messing with a different fluid is in order if the problem persists. I'll let you all know - thanks again for the "edjimicashun".

Larry Herman

There are a couple of things that you may want to check as well that will affect your braking. If your wheel bearings are getting loose, you may get pad knockback after running over curbs or bumps, which would result in a long pedal when it occurs. You said that you rebuilt your brakes over the winter. Any chance that the rotor is not properly seated against the hub. Maybe a peice of dirt/crud got behind one.

As far as ducting, you really do need a shroud that feeds air into the center of the rotor. That seems to give the best cooling. I have them on my car, but don't know their origin. BTW some pads, like PFCs tend to transmit a lot of heat into the calipers, where as others like Pagids have better insulating properties and the calipers run cooler. At least that has been my experience.

J.PELLEGRINO

I would only use AP 600 or SRF brake fluid. Anything less is just that. We have made cooling ducts that take air from the front grills via NACA ducts and use very high quality hose with a smooth inside to get the air in to the wheel well. From there, simple aluminum deflectors affixed to the inner fender direct the air right to the back side of the rotor. That is a standard upgrade and it seems to resolve most front brake problems our clients have encountered.
Good luck, Jerry

BlackWidow964

I was ideally wanting to find deflectors like those described by Larry, which push the air into the center of the hub/rotor. Anyone know a source for 964/965 applications? I have the scoops, just want a better place to route that air to than just the inside surface of the rotor.

Cupcar#12

yes - actually take a look at this idea (cheap too)
it looks pretty slick and effective
http://www.dietersmotorsports.com/tech/2002/4-2002.htm