Raysur

I have a set of lightweight Epsilon wheels for my '84 Z51 track car project. I started setting up 12" brakes today and wondered if all the weight I am saving is worth it?

Thanks,
Jeff

Solofast

I wonder how you are going to stop the car with only 12" brakes

The "big 13" brakes" from the 17" wheel cars are marginal for the track. Unless you are using some serious rotors I am thinking you are going to be running out of brakes real quickly....

Less weight is good, but if you can't stop the car it isn't going to be much fun...

c4cruiser

What calipers and rotors are you using? Stock 84-88 type? What pads are you using?

Getting lots of air to the rotor/caliper will be very important and that will help keep the brakes cool. Use a fluid with the highest wet boiling point you can find.

yakisoba

Smaller wheels are good because:
Less unsprung weight
Smaller diameter == faster (with the same gearing) than larger
Cheaper tires
Heat gets into the tires faster (less warmup laps)

Smaller wheels are bad because:
on a normal car, your brakes are inside the wheel, so wheel size dictates max brake size.
Less heat dissipation due to smaller brakes (brakes get hotter faster)
more tire wear for the same weight car then larger wheels/tires

Nascar cars get away with 15" wheels because they place the brake disks inboard of the wheels, so the caliper doesn't have to be inside the diameter of the wheel. Also, brakes on a stock car do not have to take the car from 150 down to 50 or 40 over and over again, so heat is less of a problem.

If you can live with the tradeoffs, smaller wheels are better, but for most road race applications you will run out of brakes or something will melt on you, IMO.

Raysur

I'm going to use my 12" 2 piston calipers off my '93 and make a brackets for the '84 spindle. I was going to start off with Hawk HP+ pads.

This car is a stripper and I only plan to add weight back with safety equipment. I'm aiming for 2,500 lbs. I'm going through everything, even the bolts. Anything to save a pound (I'm not fat either).

Since I graduated I want to get back into making custom car parts. I want to make a 2 piece rotor for it and get SS pistons to isolate the heat. This way can I run a ducts for the rotors.

It would be awesome to keep the rotating mass down as well as the overall weight. Are there any effective smaller brake setups?

mikahb

I think Formla 1 cars run 14" wheels, their brakes seem to work well.

Carolina C4 Racer

I think you are right BUT the weight a F1 car is alot less than 2500 lbs (Probably 1000lbs less) & 2500 is hard to achieve in a track worthy C4.
Either way if you already own a set o 16's, go for it.

63Corvette

My car races on 15" wheels and has slightly smaller than 12" rotors.......which are a HUGE improvement over the original drim brakes. Oh, and I run PFC-01 pads. I have had no problem with brakes. Enzo Ferrari was quoted as saying something like "my cars are made to run, not to stop"

parkerracing

Trans Am (RIP) and GT1 spec 16" (12"w frt. 13"w r.) The more sidewall you have the more width you need. /:\

Zee916

F1 cars weigh ~1300lbs.

Jaymz

And a car set of Hipco brakes cost alot more than that guys C4.

MistressMotorsports

If needed, there are some awesome 12 inch brake setups that the roundy round guys use. Rotors that are about 1.5" thick or so and big Willwood calipers. These guys run big, heavy V8's on short tracks that are tough on brakes. Just look at a Willwood or Outlaw brake catalogue. Might need to fab brackeets or hats, but not such a big deal.

Mike

Solofast

He said that when he was resisting the change to from drum to disk brakes... He eventually came around to using disk brakes....if you want to be fast you have to be able to stop too...

The amount of brake that you need is directly proportional to how much power you have. The more power you push into kenetic energy on the straight, the more you have to take out before you can corner...

Big power = big brakes, it's that simple... If you don't have diameter, you need to beef up the thickness of the rotors. The energy you put into the car down the straight becomes heat. If you don't have enough "thermal mass" (mass times specific heat) you will have too much temperature rise and things will melt or at least get soft and that isn't good either....

This isn't rocket science... Well maybe it is....

Raysur

Thanks guys,
I'm looking at 2 pc. rotors that are 11.75" by 1.25." I'm going to check what caliper fits this setup the best.

I just bought a scale; the wheels are 15lbs. a piece. I'm just trying to find a light tire now. Tires this size seem to weigh in the 25-30lbs. range.

63Corvette

No, it's NOT rocket science......My competitors wiegh 2000 lbs, I weigh 3000 lbs! Case closed.....,and they are better drivers than I am

Solofast

My point was that the size of brakes you need is directly proportional to the amount of power you have, and less a factor of how heavy the car is. If you don't have the power, you don't put the kenetic energy into the mass of the car, and, in that case you don't ask as much from the brakes. The weight of the car has a lot less to do with it. If you have a lighter car with the same power it is going to need as much brake as a heavy car, the light car will obtain higher straightaway speeds and therefore have more kenetic energy to dissipate with the brakes. Kenetic energy is a square of the speed, so if you are going 10% faster, you have 20% more kenetic energy to get rid of.

It is true that poor drivers tend to use the brakes more and slow down too much. Mike Hawthorne once asked Fangio why he was quicker (they were driving the same type of car) at one particular track. Fangio didn't speak much English, but replied as only he could...

"Mora speed, lessa brake"