Brake Fluid

Achilles · 05-22-05, 10:38 AM

After autocrossing my 86 last week, I'm not at all happy with the performance of my ABS. Seemed to lock up the tires a fraction of a mili-second before the ABS would activate. By this time, I was in "slide" mode....not fun. I don't know if I was driving harder than previous runs, or what. Anyway, I thought I would start with changing the fluid to see if this might help at all. Any suggestions on what fluid type to use for racing applications? What about Royal Purple? Any suggestions also to what can be done to improve the ABS system would be greatly appreciated as well.

Edmond · 05-22-05, 11:27 AM

I think a lot of guys use DOT 4 fluid for autocross but don't quote me on that. At least I gave you a bump!

c4cruiser · 05-22-05, 12:03 PM

It's pretty hard to boil the fluid on most autocross courses so a good quality DOT3 or even a DOT4 fluid should work. I would definitely do a complete flush of the fluid. I use Ford

Motorcraft HD fluid in my 87 autocross car and it works fine for both autocross and track days. It will take about a quart to do a flush.

If you are seeing some sort of wheel lockup before the ABS kicks in, you might look for any glazing on the pad surface. What pads are you using?

Driving style can also play a part. I try (I really do!!

) to get all my braking done before turn initiation so that the car is not upset once I'm into the turn. I also try to make braking as smooth as possible. I had tried to brake as hard as possible before a turn when I first started out and all that really did was cause me to brake too late and get the car to understeer which usually resulted in multiple cone deaths and injuries. Steer the car thru the apex and apply smooth throttle off the apex and thru the racing line.

Achilles · 05-22-05, 03:58 PM

Quote:

Originally Posted by c4cruiser

Driving style can also play a part. I try (I really do!!

) to get all my braking done before turn initiation so that the car is not upset once I'm into the turn. I also try to make braking as smooth as possible. I had tried to brake as hard as possible before a turn when I first started out and all that really did was cause me to brake too late and get the car to understeer which usually resulted in multiple cone deaths and injuries. Steer the car thru the apex and apply smooth throttle off the apex and thru the racing line.

Thanks c4cruser. I'll take that into consideration. I know I do tend to brake late and that could be the culprit. I first started autocrossing in our 95 and I think its ABS must be far more advanced that the 86's system, so I'm driving the car hard into the corners as I would with the 95 which allows me to do so. As far as the brake pads. I don't know what type they are. They were on it when I got it and they are about finished. Just wanted to get whatever I could out of them before I replaced them. Probably go with Hawks. What do you think? Thanks for the post.

c4cruiser · 05-24-05, 11:52 AM

From what I have read, the later ABS systems are much better than the earlier versions. I try very hard to only brake to the point where ABS is just going to energize but not to where I have to depend on ABS to slow the car. The idea is to use just enough braking force to stay below where the brakes lock-up and ABS energizes.

Hawk HPS pads are an excellent autocross pad and they should be available for the early C4's. I'm currently running EBC Greenstuff pads (both available from the Tire Rack) on my 87 and they are also a very good pad for autocross and some track use. Both of these pads are excellent for the street as they have great cold bite so you don't have to to worry about not having heat in them berfore they start to work.

I had run Hawk HPS pads on my 92 and they are a very good autocross pad but the dust was horrible. The EBC pads also dust somewhat but nowhere near as bad as the Hawks. Performance Friction Z-Rated pads are good too.

One problem with the early C4's is a lack of really good street/autocross pads. That's mostly due to the smaller front brakes compared to the later cars. If you have a set of Enkei-made stock 16" wheels, the later 12" rotors and calipers are supposed to clear. But that would take you out of a stock class so if you are consiering bigger brakes, go with the 13" J55 setup and 17" wheels. Also consider changing the brake bias spring to get a bit better braking from the rear wheels.

My EBC pads are about gone so I'm going try some Hawk HP+ pads this season. My front rotors are about gone but I buy the cheapie "White-box" rotors and just toss them when they are toast. Most of the lower-cost slotted and drilled rotors will crack from the extreme heat from track day use and I really don't want to spend thousands on race-grade stuff.

Rotors that have the holes drilled after they are cast are the ones to avoid. Drilling places stress in the metal around the holes and that's where the craks begin. Some slotted rotors can be noisy; the edge of the pad hits the leading edge of the slot and you get squeaks on the street.

Achilles · 05-25-05, 10:18 AM

cruiser, I appreciate your input. When you say "White box" rotors, are you implying just a generic rotor? Also, I don't think that the excessive brake dust from the Hawks would be an issue since this car is really only used to race and we trailer it to race events. I'm more interested in better performance, but I have to be carefull that I stay within the stock class. I forgot about the brake bias spring though. I remember seeing that somewhere in one of the vette catalogs. Do you remember off hand who has them?

Thanks again for your help.

Achilles · 05-25-05, 10:20 AM

Oh, I forgot to ask...Why Motorcraft fluid?

Edmond · 05-25-05, 11:03 AM

Last I read, Doug Rippie has the bias spring for the brakes.

Here is is at www.dougrippie.com

1987 - 96 Corvette ABS10-100$12.95 1984 - 86 Corvette non-ABS10-101$12.95 1997 - 00 Corvette10-102$12.95

Just click on brakes on the left side of the screen and scroll down.

froggy47 · 05-25-05, 05:34 PM

Quote:

Originally Posted by c4cruiser

It's pretty hard to boil the fluid on most autocross courses so a good quality DOT3 or even a DOT4 fluid should work. I would definitely do a complete flush of the fluid. I use Ford

Motorcraft HD fluid in my 87 autocross car and it works fine for both autocross and track days. It will take about a quart to do a flush.

I agree, it's cheap & good. Flush 2 or 3 times a race season.

c4cruiser · 05-25-05, 07:55 PM

Quote:

Originally Posted by Chickenjerk

Oh, I forgot to ask...Why Motorcraft fluid?

The Motorcraft fluid seems to be pretty popular with autocrossers and those that do occasional track days. It's available at any Ford dealer. Other good HP DOT3 and 4 fluids may be hard to come by at localt auto parts stores.

Castrol LMA is another good fluid but the local Shucks and AutoZone doesn't carry the LMA, just the regular Castrol fluids. LMA is about the same price as the Ford fluid.

Other good DOT4 fluids are ATE Super Blue and ATE TYP200 (they are the same fluids, just different colors. When you flush one and install the other, you can easily tell when the new color comes out of the bleed valve.). For road courses that are long and have lots of heavy braking, use Motul 600 or Castrol SRF. These are more race-grade fluids and have very high wet boiling points.

And "white box" are the generic ones. I get them for cheap at the shop where I work. Brembo makes a standard 11.5" front rotor that is probably of better quality. Raybestos makes good standard rotors. Check out NAPA too.

If you don't care about tossing rotors after they are used up, the generic ones work great. Just have them checked for runout, sand the suface for a good non-directional finish, and do a really good cleaning on them before installing.

Achilles · 05-26-05, 09:29 AM

Thanks everyone for your help and advice. I am planning to take the car out this weekend and do some braking tests so I have some before and after results for comparison. C4cruiser, I really appreciate your input.