Last weekend at the track, the car began to suffer from loss of brakes due to over heating, after a few laps. Had fresh brake fluid DOT4, but it was a hot day, in the 90's. Does anyone have experience with cooling options / ducting / etc. for a C3? Is it always the front calipers that overheat? I was running 86 wheels with adapters and slicks, I thought the 86 aero style wheels would provide better brake cooling than the rallye wheels.

Any suggestions? Thanks in advance...

Joe

 

I thought you could reduce brake fade with different pads, so I did a Google on "brake fade" and "pads" and found a link that may be informative...

http://www.tirerack.com/brakes/tech101.html

Just be cautious, I don't think that the article goes into it, but some pads that are "fade-resistant" may not be appropriate for street use because they don't become effective until they get hot.

There are always larger rotors, six-piston calipers, and such, but the pads may be a good starting point (if you haven't already experimented with different ones).

 

Thanks Jerryp58,

I am now using competition brake pads. They are not too bad when cold, and improve when hot. I did in fact have much worse brake fade problems on the original soft compound pads, so I converted the car to power brakes to use and compensate for the competition pads.

Of course, as the lap times get better, the brakes are working harder :) especially with the extra grip of the Hoosier slicks. So I was hoping to duct some more air to the discs, to avoid major brake upgrade, and thought there might be a kit to do that.

Thanks for your help. Perhaps others might have some suggestions for me as well.

Joe

 

I have a nifty front spoiler with inlets for connection to brake cooling ducts. It hangs down a bit lower than stock so it is probably for track use only. Contact me if you are interested in purchasing it.
will_shepherd@hotmail.com

 

I made a similar thread to this one a few months ago, and clutchdust responded describing his homemade brake ducts, and he said they worked well. Hopefully he'll chime in. I haven't gotten around to trying it yet on my car.

 

One thing you might want to try is to change over to dot 5 brake fluid. Im sure you know about it, but its silicone based and has a much higher boiling point (over 500 deg F) than dot 3 or 4.
you cant mix it with anything except dot 5 and it is much more expensive. The only other thing to watch out for with the dot5 is that it isnt hydroscopic so it will not absorbe moisture. Any moisture in the system will generally sit at the lowest points and start rusting parts. This isnt a problem as long as you change you brake fluid on a regular basis.
Kevin

 

Hello Joe, Remove those dustshields at front and cut em at rear . use best brake fluid you can find( i love motul) and get new sloted hd rotors (dont drill em wont last !) and finally get new brake bads from here : http://www.porterfield-brakes.com/

These worked for me

 

chiming in! i have run several track events and have had very little problems with brakes with the mods i've made. as for brake ducts, i fabbed some from some old pool hose and a couple funnels i got at wal mart. i got this black funnel with a small tab at the top and heated them to flaten them out somewhat. the tab was a perfect place to bolt them under the front bumper. i fit the hose (1.5" diameter) into the funnel and then cut the funnel off just below where the hose slid up, then bonded them together. the hose then just runs between the frame and anti-sway bar to the lower a-arm where it is held in place by some 'plumbers' tape bolted to the lower a-arm bump stop. i'd love to put larger ducts in but i am space restricted so i'm making due with these. so far i haven't had any overheating problems with them and they are alot cheaper to make, and in the case of my field plowing episodes in buttonwillow last week, they are cheap to replace. :bb
the other mods that i feel are invaluable if your going to do alot of speed events in a c-3 are 1) brake fluid [i'm running blue oval d.o.t. 3] 2) pads, i'm using over the counter performance frictions i got from autozone for $35 with a lifetime warranty. they're not the best i could run but beat the hell out of the factory organics. 3) russell steel braided teflon lined brake lines. 4) a proportioning valve. i think this is the single biggest improvement you can make of all of them. the reason is that the weight transfer and rear spring have a tendancy to jack the back of the car up during heavy braking causing the load the rear tires see to lighten significantly. obviously, the rear tires then want to lock up and the supercomputer behind the steering wheel determines too much braking and eases back on the pedal, thereby increasing the stopping distance. installing an adjustable proportioning valve on the rear allow you to reduce the brake bias to the rear so that the fronts lock up just before the rear. it will take a few times of romping on the brakes to get the bias figured out but once you get it set up, you will be able to brake deeper and harder into your turns.

 

With respect to Kevin, most serious racers use Fomoco ("Blue Oval") Dot 3 or 4. Don't ask me why, but this stuff flat works better. Some folks have good experiences with Dot 5, but the most common complaint is a softer pedal "feel" compared to the other. Brake fluid performance degrades quickly if you don't change it regularly (typically after 2-3 sessions on a race weekend, and for sure right before the main race). I agree with cutting the backing plates and running as large a duct as possible to the fronts.

P.S. keep a close eye on the rotors. They WILL overheat and you need to watch for cracking and grooving on a stock system. Larger drilled and grooved rotors, and better calipers are probably the single best thing you can do to improve lap times.

Hans


[Modified by Wrencher, 11:50 AM 11/20/2002]

 

Thanks to all for your help.....I really love this forum, I hope I can help others sometime.

Flynhi,
Thanks for the offer, shipping to Oz will be a killer, do you have any photos of the spoiler? perhaps I could fabricate something similar here.

Aharte,
I followed up on that thread, and Clutchdust has also replied. Some good ideas there.

Kevin,
To use DOT5 I assume you have to dismantle and completely clean all of the braking components to eliminate older brake fluids.

Joni,
Thanks for the tip re backing plates. Do the rear brakes overheat or is it just the fronts?

Clutchdust,
Thanks for the ideas, I think I can make that work. My brakes seem to be well balanced....front's locking up just before rears, so I'll leave proportioning valve till later. Did you remove backing plates on front? Where did you aim the air from the duct? Sounds like you taped it to the lower bump stop and pointed it into the area between the rim and backing plate? Did you have overheating problems before or was this a precaution? Did you have any overheating problems on rear brakes.

Wrencher,
Thanks for the tip and warning. Seems there's always something else to consider, when you improve something, you can go that bit faster & stop that bit better, it will often take something else past its design limits.

Best regards,
Joe

 

Hi jyounane!

Glad to help .As for rear brake overheat ,i have no recorded data to back it up but C3 whellwells arent wery open, so i thought extra cooling wont hurt and keeps rotors safe.

 

Hey I got a questions along these lines. I been building a twin turbo block for my vett, anyways the exhaust was best "and only way it would work" was to go right where the stock master cylinder sat, and down and undr the frame and off to the back.. Anyways this made me go out and fit a 87 master cylinder and brake booster on, and also having to extend the cylinder about a foot forward. Anyways my brakes suck now. . I didn't look into the volume displacment between the 2 cylinders, I would think the 87 cylinder would push more fluid than the 80. Oh and I also had to change the lines to I believe to the smaller size line that the 80's have, I don't remember for sure, but anyways they guys at the shop said it would not be a problem. Well something is a problem.. Anyone have any info on this?

 

DOT 5 is NOT for severe use. To decrease fade, you must control heat, for two reasons:
1-coefficent of friction is a function of temp, and is inversely proportional
2-high temps can boil brake fluid, resulting in fluid compression

To control temps
-use high-performance pads with a more constant and greater friction coefficient. combine with a rotor of quality material and proper surface finish.
-larger rotors for a) more mass for more heat absorption, increased convection surface area for cooling b) more mechanical leverage for increased stopping power, resulting in more cool-down time in the cycle
-ducting, vented rotors, open wheels
-reduce the weight of your car... :p:

What about applying some conducting paste between the rotor and spindle face? this would effectively increase the mass of the rotor, allowing heat to move to the spindle much more easily than if were just metal-metal contact. might cause bearing clearance problems if heat it too much though...



[Modified by Turbo-Jet, 11:42 PM 11/20/2002]

 

Joe,i did exactly what Wrencher said and cracked the disc at phillip island(amongst some other brake issues like boiling the fluid) before last weekend at winton,new pads,new rotors,new caliper seals,new blue oval fluid,no fade at all....but the fierce under hood temperatures(not engine temp thankfully)was a real problem,i was getting intermittent fuel evaporation and flooding from subsequent surges....if i am going to race again on such a hot day i will have to find some way of getting the hot air out from under the hood......the brakes were cool enough with some simple flex duct from the front grill to just infront of the brakes......they also run much cooler than when i had the rally wheels on...john :chevy

 

joe, the 'plumbers tape' is that metal strapping with holes all the way down it so you can wrap it around the hose and bolt it down. and yes, it is bolted down to the lower bump stop and pointed right at the center of the spindle. also yes, i removed dust shields front and back. i did have overheating problems earlier this year at willow springs. that is the main reason i decided this needed to get done. both the rotors and calipers got extremely hot, the fade wasn't that bad but when i pulled the rims off that is when i got the whole story. if you've ever seen cast iron after it's gone through a fire, thats what the rotors looked like anywhere other than the pad surface. the calipers weren't much better.

washingtonracer, i'd think the c-4 master cylinder wouldn't push as much fluid as the original. remember some early c-4s had single piston calipers and even the dual piston calipers likely didn't require as much fluid as our four piston calipers do to apply sufficient clamping force. you should really talk to some place like VBP or wilwood to get a fair comparison.