Brake Performance or lack of.

[Arm7419]

I've always been concerned with the brakes on my 33. I did the disk and pad changes that were mentioned in a forum thread, with little improvement. Today I checked brake pressure at the calipers and only recorded 400 psi at each caliper. I believe this figure should be 900-1200 psi. Has anyone ever checked their brake pressure? To get a higher pressure I would need to change to a larger master cylinder. With the body on this is impossible on my car. Anyone have any thoughts on brake pressure and stopping performance on the Hotrod?

Chuck

[4wheelspin]

I contacted Wilwood a while back for some info. I'm using stock mustang calipers with the upgraded disc and pads.
Heres what they had to say:

With your current setup, you should see about 700 -800 psi at the calipers.
Using any smaller bore size to increase pressure will not provide sufficient volume.

They also mentioned to adjust the balance bar.

I left it at that for the time being. I'm not satisfied with the braking performance of the car.
My brakes are not beaded yet, but I really doubt the braking will improve to the point that I will be satisfied.
I'm looking into a power brake option that will be mounted under the dash.

[hdnik]

4wheelspin,

Do yourself a favour and call or email Jeff collins at Whitby Motorcar. He has just released a power brake conversion for the 33 using a conventional vacuum booster, with and without remote resevoirs that can retro fitted in a completed car. Its just new and i dont think its on his web site yet, but based on his cobra kit... It should sell for about 400 complete.

I just installed it on mine and while im still in the build stage and it was quite easy, i know Jeff has installed the same thing on 2 other cars that were built and can attest to their performance improvements over stock setup.

Here is my link to my brake build http://thefactoryfiveforum.com/showthread.php?10226-Power-Brakes-installed-on-the-33


Call (336) 389-0904

whitbymotorcars@aol.com or info@whitbymotorsports.com

[tirod]

The real issue is sizing the brakes front and rear for the amount of weight bias - if the car is 49/51 like the roadster kits, the rear brakes need to be the same size as the fronts. In that specific case, many who installed the dinky factory donor rear brakes have complained about poor braking. And, they should, they have 51% of the weight on that axle with a caliper half the size to do the work.

Once the brakes are matched to the work they need to do, then choose the master cylinder(s) that will operate them.

What's been happening in the kit world is using whatever brakes the donor had because the focus has been on the engine, transmission, and differential. All the spare funds are diverted to dressing up the motor and the brakes are largely ignored. Almost nobody checks the actual pressures to see what the system is really doing - they spend that money going to a dyno.

You have the right approach, look into what brakes are needed for your car's particular weight bias, what master setup is needed to operate them, and just do it. Once that happens, the brakes will be magically improved overnight, and it will be a lot more fun to drive.

First question, what's the weight bias on the car, what percent front and rear? A local scale can help axle out the numbers, it's easy.

[Jim Schenck]

If you are running SN95 mustang rear calipers with the 38mm pistons then changing from a 3/4 to a 5/8 master cylinder in the rear will make a big difference. You can do the change with the body on, as long as you have the cut-outs for filling the reservoirs to reach through.

[Arm7419]

Jim

Why not change the front master cylinder also and get much needed brake pressure. That is if I can get at them

Chuck

[Jim Schenck]

The front 2 piston calipers have to much volume for a 5/8 to handle, also because of the small diameter of the rear piston the brakes will be easier to balance out with the split master sizes without cranking the balance bar out to the max. Just changing the rear makes a big difference though, I don't think you would want a softer pedal or more pedal travel after you have tried it. Also what pads did you change to?

[Arm7419]

Jim,

Thanks for the explanation. I'm not home to answer your question concerning brake pads. Will tomorrow.

[Arm7419]

Jim

I'm using Powerstop Evolution Ceramic Disk Brake pads. These were suggested in some thread on brakes for the 33. Any pad suggestions

thanks

chuck

[CHOTIS BILL]

I had pressure gauges on my DSR and the normal pressure was about 300 to 350# for the rear and about 600# for the front with 4.5:1 pedal ratio and 47 / 53 front / rear weight bias using 5/8 master cylinder front and rear, and it would suck the filling out of your teeth. But it only weighed 1035# after a race with me in it.

Bill Lomenick

[Jim Schenck]

Chuck,

We have had good luck with Carbotech #8 compound on street cars, although my preference is to go even more aggressive. The Carbotech #10 or Hawk DTC 60 compounds will definately produce more dust than most street pads will but they make a huge difference in pedal effort. I have heard many people say these won't work when the pads are cold but my experience with our lightweight cars has been they are better than any street pads when they are stone cold and then they get better with a little heat in them. Even if you go with the #8s you will see a big difference, but I would still swap out the rear master before I did anything else.

[robboy]

I switched the front and rear masters out for .7 and .625 Wilwood masters. Big difference in pedal effort to stop the car but a slight increase in pedal travel maybe a 1/2 inch. I also switched to the Powerstop rotors and pads for further improvement and I think that a more aggressive pad material will yield even more improvment . I have also spent some time adjusting the balance bar but this seems to be more micro than macro. Also I have larger rear rotors on the rear than on the front(11.67 vs 11 ) but the rears are single piston and the fronts are dual piston. The car stops good but not great, I think. I haven't measured any 60 to 0 distances but I have a feeling that they are better than my seat of the pants tests tell me. This car doesn't dive much to the front under heavy braking and I think that gives one a false impression of how well the car is stopping.

[wallace18]

Chuck,

We have had good luck with Carbotech #8 compound on street cars, although my preference is to go even more aggressive. The Carbotech #10 or Hawk DTC 60 compounds will definately produce more dust than most street pads will but they make a huge difference in pedal effort. I have heard many people say these won't work when the pads are cold but my experience with our lightweight cars has been they are better than any street pads when they are stone cold and then they get better with a little heat in them. Even if you go with the #8s you will see a big difference, but I would still swap out the rear master before I did anything else.

Jim do you have part #'s for these pads? I have the ffr rear disk upgrade. Thanks.

[Jim Schenck]

Carbotech is CT627 for the 11.65 rear rotors (what comes from us unless you have the older solid rotors). For our fronts it would be CT804, then you just specify the compound you want, 8 or 10

[wallace18]

Thanks Jim.

[Arm7419]

Changed rear MC to 0.625 bore. Remarkable difference. Was able to drop the pedal box down and out. Difficult and messy but worth it. Also put jam nuts on one end of balance bar and MC pushrods so they will be able to be adjusted if needed in the future.

Chuck