FASTFATBOY

Can someone help me out here? Not enough cooling air? Too much cooling air?

Car is a 3800lb Z28 with 385 rwhp, this turd will touch 140 mph down the front at NOLA Motorsports Park, turn in for turn one is about 65 MPH.

I am on BFG R1 tires.

Pads are the Wilwood "H" pad on front and Hawk HP+ rear.

This is Wilwoods kit 140-7190 for the F-Body, but I put a 13.06 rotor on it in place of the 12.88.

Left front rotor, three cracks like this in this rotor. No cracks to the edge in the right front rotor.




Right front rotor, inside and pic of ducts





Left front pads




Right front pads




Air intakes




Rear rotor





Here is a vid on track


Any help is appreciated.

0Todd TCE

You know I'm not so sure 11 sessions on those rings at this weight and speed is really not too bad. I'd look at taking more weight out of the car for one. And I'd consider a more aggressive rear pad possibly. If you can get the rears to 'do' a bit more you might relieve some stresses on the front. Right now I'm sure you're overly front biased.

Is that 3800 including you or just the car on the scales. If FASTFATBOY represents another 250lbs behind the wheel you're pushing a lot of weight around here. No matter how you slice it; weight is the enemy of brakes.

I'd also look at fitting some pad wear spacers preventing so much piston extension. That'll help with piston/bore compliance and lessen the chance of pistons getting hung up as well as lower the taper wear a bit.

Air ducts look good. Never figured out why some sides run hot or cold tho. Seen it on a lot of cars but never had one in a wind tunnel!~

FASTFATBOY

Its about 3750 sitting on track with me in it and full of fuel.

You can't put a more aggressive pad on the rear of these cars as they wheel hop pretty bad.

I just ordered caliper heat strips and am going to change the duct setup to this.




This a street car that sees DE duty, no weight to take out.

Where can I get pad spacers? This is a 7420 pad shape.

Hi Volts Z06

Given the weight of the vehicle, the fact that you are using a street pad in the rear and the small diameter of the front rotor, I'd say your results aren't atypical. I think you need to dial in the pad compounds for both front and rear first AND make sure your hydraulic bias is correct as well. Your proportioning might be off. You can get small gauges that attach to your bleeders that will show pressure at each corner. Check those first.

Also you might want to try a better quality rotor. I'm not bashing Wilwoods, just saying you could use it as a baseline and then try some rings from say, Stoptech.

Hi Volts Z06

BTW you can make pad spacers yourself from a set of worn pads. Just grind down all pad material and use the backing plate as a shim. You do have an excessive amount of piston travel. Are you sure they don't offer a thicker rotor?

JDIllon

I would like to make some suggestions. 1 I would try Cobalt pads, I have had much better rotor wear after changing to them. Also, I would try to get your air intakes for the brakes up on each side of the radiator. I have found that the location you have them, at least on a vette is not a high pressure area even with the air dam. Just my .02 and some thing to think about. JD

FASTFATBOY

This is because the pads are .800 thick when new, 7420 pad shape.

You can't put an aggressive pad on the rear of these cars, they wheel hop if you do.

I have tried the more aggressive pad on the rear, it lengthens breaking distance as you have to get on them earlier and longer because of the brake hop issue.

LS1RAFTRACER

Having driven a nose heavy 2000 Z28 for some time in SOLO II, the brakes take a pounding for the weight proportion and displacement. Once I got the car corner weighted the braking issues lightened up. Also, if you are running a street tire/track tire the brakes have to compensate for the lack of grip vs. a true track tire.
Your video suggests that you are pushing the car (good)and the brakes are giving it up for your performance (bad). On the other hand, that may not have been parsley in those brownies I ate.

RAFT

redtopz

Best solution would be 14" front rotors and 13" in back. I found going from 13 to 14" front rotors made a huge difference in rotor life. Also I agree your cooling duct inlets are in a bad location now and moving them to the front bumper is a good idea. I also would try to solve the wheel hop issue with shocks/springs and go with more rear brake bias. I'm sure there are solutions to wheel hop but you might have to spend some $$. I remember when GM solved the accelerating wheel hop issue on the CTSV's by using different size half shafts. Perhaps even some rear downforce and changing rear shock damping would solve the problem. Oh and I would get that right hand looked at .

FASTFATBOY

BAD Carpal tunnel, gotta get it fixed.

Here is what I've been playing with today. Ducts up front, using the frail rail as plumbing.








Here is the car I am copying.

Apocolipse

Car is a 3800lb

wow...try and shed some poundage and will help you out a bunch.

Soloontario

I used to track a 2002 Camaro. Putting in a rear proportioning valve after the ABS module got rid of 95% of the dreaded wheel hop.

<OTOH, I agree that with the speeds and wgt you are seeing, you can´t really expect a ton more of those front rotors.

J.R.

I agree with what Todd and Bill said.

3800 Lbs in 11 sessions on 7420 "H" pads is not unrealistic, especially if you are aggressive on pressure application (not a bad thing). I believe with those calipers for 1 3/8 in rotors you are limited in rotor size. Todd would have an answer for sure.

I raced a 2002 Speedvision Challenge Camaro before my Vettes, If you PM me I may be able to give you some help on setup (spring rate/shocks/rotors, pads, etc) to assist with brake issues. You are correct that in order to get correct bias,without separate master cylinders, you may have to race with different rear compound but as Bill alluded to, larger rotors, setup changes etc.may make brakes work better.

I had really good luck with 7420 'H" compound when I raced with Wilwoods but I was also 400 lbs lighter.

FASTFATBOY

I may put the C6 Vette brakes back on the car. I was getting 2 weekends out of a set of $60 each Brembo blank rotors. Brakes were not as good, but cost was acceptable.

0Todd TCE

Pad wear plates: BOTTOM OF THE PAGE





No disrespect to other pad brands but the thermal issues show are not a pad problem, they are a heat problem. Assuming he doesn't slow down or make the car lighter the same BTU is being generated. The thermal dynamics remain the same for the same net braking. But...

On the other hand a later, shorter and more aggressive brake application might produce the same slowing but keep the peak temps for a shorter time. Often I've seen folks brake at the 4 marker dragging down the car all the way to the apex rather than braking harder at the 1.5 market and quickly scrubbing speed transitioning back to power by the apex. Take a bit more moxy for drivers to do it and weight transfer is quicker so the power application has to be more sure footed also.

Just some thoughts. I do like the 14" idea but that won't work on these calipers. They top out at about 13.6" max for fit. That would require custom rings and the correct barrel spacer on the stud- assuming you don't run out of thread for the nut! lol

But yes they will go 1.375 wide also. Again limited options and a width change means a hat or bracket change as you are moving the centerline by 1/16 from where it is now. (unless you do custom rings with a countersunk hat mount- done that)

Apocolipse

If you go dual masters, how do you spec the size on the front and rear? I realize that it's all about hydraulic ratios, but won't a smaller piston need to move a bit more than the larger one and make the pedal bar go a bit sideways on an angle? I guess same can be said about front pads wearing faster than the rear...

0Todd TCE

Twin mc's are great to talk about but totally impractical for the normal street car. Dedicated track car; fine. The amount of work needed to mount and plumb them is rather larger. Doesn't mean it can't be done of course.

Sizing is based on what you have for calipers on both ends and a ballpark starting point for bias. Also pedal ratio and what the driver likes for feel. There's no one size fits all for the spec.

For what he has here....I'd wager perhaps a 13/16 front and 3/4 rear. Higher rear pressure but far less piston area and visa-versa the front. I always suggest folks expect to make a change despite the best thoughts. But most are cheap enough that if you buy 3-4 to get what you like for feel it's not expensive.

You can calculate some data here: DUAL MC and BIAS Calc

You could start also by using the single mc calculator for determining your front line pressures now (close) and trying to obtain that and the same rotor tq via the dual mc. Yeah..it's time consuming.

Solofast

Changing MC sizes, going dual MC and putting lower bite pads on the back are all band aids on a stab wound... If you're limiting how much rear brake bias for any reason other than the car getting loose under braking, you are going in the wrong direction. More rear bias will take braking load off of the front end. If the rear axle is hopping, the fix that first with shocks or better axle control. While generally you can't replace all the bushings in the rear end with poly because it will bind up, you can do some and gain control. Also look at shocks and rubber mounting of the shocks.

Generally axle hop is a result of relatively small motions that are caused by bushing stiffness, so I would look there first, and that includes the shock mounting bushings. There are some ball and socket shock mounting setups that are available that will probably help if you have pin top shocks, if not see what you can do to take some of the rubber out of the system and that should help a lot.

Once you tame the axle and increase the amount of work the rear brakes are doing that may take the temperatures down in the front. And the car will turn in and rotate better if it isn't over loading the front brakes.

FASTFATBOY

The only REAL fix for axle hop is a decoupled torque arm, at $1000 that option is out.

This car with stock C6 base brakes gets 2 weekends out of a $60 each Brembo blank rotors vs one weekend out of $200 each Wilwood rings.

That is totally unacceptable to me.

Here are my options:

I have a line on a BIG RED Porsche BBK for the car with 13 inch rotors. These rotors are a lot more heavy duty.

Sell my 4 sets of 17 inch wheels, move to 18 inch wheels and put a 14 inch rotor on the car.

Put the C6 Vette base brakes back on the car. Not as good, pads are more expensive but at the end of the day much less maintenance and less money overall.

Solofast

Not familiar enough with your car, but most of the deflection in axle wind up is due to bushing deflection. If you get rid of some or most of that you'll greatly decrease the onset of hop and that might let you get to where you need to be. Bushings are cheap (relatively) and proper axle control is important anyway.

I know it sounds expensive, and this isn't what you want to hear, but you have a very heavy car with good power and you are running the front brakes off if it because you're asking them to do more work than is reasonable.

Yes, you can keep going to bigger and bigger (and more expensive) front brakes, and then you can spend big bucks to maintain them because the parts are expensive, but since you're still overloading them and they are going to cook anyway.

Or you can try to increase the amount of work the rear's are doing. Maybe with a set of bushings you won't get to a perfect solution, but it will let you increase the rear bias until it starts to hop again, and that will take some of the work off of the front end. Perhaps you won't get all the way to an optimal solution, but you will do that once. Trying to do it by brute force you are going to spend money all the time on maintenance, and in the long run you'll spend twice as much and had twice the hassle of doing it right the first time.