dcvee

Ok. So the rear brake has less torque arm, smaller piston area and proportioning right from the factory. Being new to the C5 Vette platform, why do all of you guys run less aggressive pads on the rear?

What's wrong with a square pad setup to help take some of the work off the front rotors? Are folks losing the rear under braking on corner entrance?

Thanks,
Don

Jason

People do it to change the brake balance. I'm not smart enough to figure it all out, so I just run the same front/rear.

dcvee

Yeah, figured it was a balance thing, but that's kinda my point. The rear rotor/piston volume/proportion already takes care of that. Must be because of the extreme weight shift on corner entry on the front tires. Hence, you can run a more aggressive pad there to take advantage.

I'm kinda new to road racing....the racing I did never required brakes unless you were backing out of the trailer...so I'm touch behind the curve!!!

Don

WNeal

Don,
I have been running DTC-70s all the way around and have been very happy with it.

davidfarmer

that's not really it at all, not directly anyway. A C5 at full braking has 70% front load, 30% rear load. That translates to around 1000ºF at the front rotor, and only around 500ºF at the rear rotor. If you run the same pads, you'll be out of it's heat range on one end or the other. Usually you need a super high temp pad for the front to achieve the same grip as a standard racing pad will give in the rear.

Just like comparing street tires to racing tires. Street tires are sticky at ambient temp, get greasy at the track. Track tires are awefull when cold, awesome when hot.

You have to pick the pad that offers the right grip at the right temps. Porsches with 65% rear weight bias have very similar braking potential front-to-rear, so they can run similar pads front/rear.

trumper Z06

Great explaination !!!

ZR1 MK

Thats true for a stock car, but not for a modified car.

Ive always used the same pad compound front and rear. All my cars have been modified, always using a proportion valve. Pad CF vs temp isnt as critical as I run about 150 degree less temp in the rear. I prefer using the same pads front and rear that have the same characteristics.

kentz06

davidfarmer

I'm not saying you can't achieve balance running the same pads, but why run a pad that is designed to operate at 800-1200deg on the rear where it will only see 450deg?

You can balance a system with pads, calipers, rotors, bias valves, whatever, but a race car should run the optimum component for the job, and that means a hotter pad in the front of a Corvette.

A severely modified car can overcome this. If you either have moved a lot of weight to the rear, lowered the COG a LOT, or added lots of brake cooling to the front, you can reduce the temperature difference some.

flink

The manufacturer's front/rear biasing will have been designed with street tires in mind. ie: 1G braking.

Once you put gluey tires on there you're braking at 1.2G or more, and there's more weight on the front (and less on the rears) than the designers expected.

So.... with the stock brake setup one would expect that the car would benefit from a slightly lower friction coefficient in the rear.

But as was mentioned, Cf varies with temperature and the front and rear rotors run at different temperatures. However this doesn't necessarily mean that the rears run cooler! They're smaller and have worse cooling...

dcvee

Ok, that makes sense too. Has anyone ever used temp paint to check that? I would think with the smaller surface area of pad the temperature would equal out...

When I first bought this car it had xp10/8's on it and I must admit, they were great. However I get a smoking deal on Hawk stuff so I'd like to give them a try. Also, I was just thinking of an opportunity to put some more load on the rear to maybe stop cracking front rotors every other day!!

Thanks for the answer!!
Don

dcvee

Ah, ok Bill!! I'm going to give it a try. At least while I'm learning it shouldn't make a huge difference. I'll have to be careful with my square tire setup however....running 275x18's on all 4. That could make the rear dance a bit on corner entry.

Don

JMB92

Dave is pretty much right on, it's all about vertical load and tire contact patch for balance. Think about these as you adjust, or you could monitor your wheel speed sensors over CAN like I do . . . . .

I did some temp monitoring, remember this is a T1 Race car at Road America, so your temps will be WAY lower, but for example. (wonder why they faded)

Front Rotor (Paint on Vane) 1600-1800 deg F
Front Caliper (Strip on outer bridge) 536+ deg F
Rear Rotor (Paint) 1076-1328 deg F
Rear Caliper (Strip) 425-450 deg F

dcvee

Great info...BUT, were they different compounds front/rear??? What data collection system are you using?

Thanks!
Don