Brake experts, advice please.

Howard Jones

Supporter
No they are not boosted. I think the 4.0 to 3.0 ratio is a pretty good one. If you can exchange the 1.62 for 1.75 I would do that. If not, you can use the 1.62 fronts and the 1.38s in the rear that you have, I think you will be pretty close.


If you are using street tires on the same wheel all the way around instead of wider wheels in the rear with wider tires then you might start with the rears that you have on the car for now with the 1.62s in front.

Check out the flexing mount thing first for sure and fix that if you have to. Also be sure your master is good.

After that I going to be a trial and error thing. The P valve will help if the rear are a little over biased.
 
Here's my guess...

Your front pistons are too small. The mechanical part of your brake system at the pedal may be flexing (firewall, the pedal itself, etc.) because having made the caliper pistons smaller you are moving the piston more relative to pedal stroke (ie. caliper piston size v. MC piston size). The smaller you make the caliper pistons the greater pedal pressure required to exert the same clamping force on the caliper....perhaps to the point where the mechanical actuation at the pedal is over powered.

I would be surprised if you're flexing the calipers.

Just my guess.

Decreasing the caliper piston size will also reduce modulation at the limit of luck up.
 
John,
Looking at the photos of your calipers, your rears have a bridge bolt however the front superlites are drilled for them but do not have them fitted. You will find (as i have) that the front calipers flex considerably without the bolts fitted. Some grade 12 bolts work fine.

Regardless of anything else you do (as suggested by the many experienced guys here) please at least make the calipers rigid by fitting the bolts. The best 2 bucks you will spend in my opinion

For what it is worth, my gt40 uses 4 piston superlite front with 1.75 pistons, dynalite rear with 1.75 pistons and dual 0.75 master cylinders. Street pads are ferodo ds2500 all round and on track i use willwood "a" compound on the front with a slight bias bar change. Stopping is easy
 
Rick, the fronts do have bridge bolts, 2 each, but they were not installed in that pic.

I don't think putting the 3.0's I have right now in the rear will ever work out. These cars are so touchy about rear lock up and bearly need any rear brake. The bias I have right now is perfect, and I will have to maintain that ratio. if I go to 1.75 pistons in front, that is a 60% increase from where I am now, I will most likely have to get 60% larger rears as well.

The new fronts I just got are a 37% increase, I think I might be gambling, but that might be enough.
 
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Howard Jones

Supporter
My advice is to use what you have and see where you are. I would rather you get the car to the point that you can lock the front tires if you try without putting your foot through the firewall. The rear tires should be still turning at that point and with a bit more foot pressure then the rear should stop turning.

Not touchy, but if you really want to, you should be able to stop the tires from turning at all speeds.........Some times you need to just lock them all up and wait until the car stops when things don't go as planed. If you can't slide it to a stop then you are left with only the option of steering out of a slide. This will usually end up in the wall.

Then if the car does that and is comfortable to you then you are done with the basic brake balance. Next you might start to try and tune out the rear twitchiness. By the way do you have a limited slip in the rear end and if so what kind?
 
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had the calipers off today and noticed I was low on pad. I ordered new ones which are supposed to be a little more aggressive. I think this is going to work out.

I do have a lsd, it's an auburn racers unit. It's an interesting diff. It seems to work all right in this application.
 
When I was talking about the rear end being touchy, I meant to say it was about wheel hop. The car is otherwise stable when breaking. But this rear suspension is natorous for inducing wheel up. It's a torque arm setup, and from what I understand, this is just a part of that design.
 
Its clear that these cars were never designed to be on a road course, but wow, it seems the Mustang, especially the SN95 ones, were much worse off than my 3rd gen F-Body. They are very similar in many ways except when it came to the rear suspension. From the factory, the 3rd gen's came with a torque arm and panhard bar. Though, the torque arm has its own challenges, one of them being, iirc, very short instant centers under braking which induced wheel hop. You can counter this by changing the angle of the lower control arms, but then you lose some of the ability to put power down. My solution was to limit the amount of dive by installing massive rate springs in the front, which in turn limited how much the rear lifted under braking, this seems to be working. Even though Mustangs and f-bodies have strut front suspensions with inboard springs, I seem to be able to get acceptable camber and caster, around 2 or so degrees of static camber and around 5 or 6 degrees of caster. I dont know what the mustangs can get. Its a compromise like all suspensions are, but more so with this.

If you put on all that Griggs stuff, especially their front suspension, is it even a mustang anymore?

I did pass a fox body mustang at the track day last monday like he was standing still :cool:
 
Finally was able to get my new calipers on and test it out. Brakes feel great so far, but that was on the street in the countryside. Taking it to the track next week to really give it a work out.
 

Ron Earp

Admin
, especially the SN95 ones, were much worse off than my 3rd gen F-Body.
I've been racing Mustangs for a number of years. The 79-04 years are all basically the same. Quadrabind rear suspension, various length lower arms and subframes up front with the best geometry being the later variants.

There are lots of fixes for any of the problems and it doesn't need to be converted to a Griggs tubular setup to work, not at all. It does need to get a panhard or watts in the rear though. No doubt.

That said, I have run two races in a enduro event in a 1995 Mustang (SN95) with essentially stock quadrabind rear. It isn't as bad as stated in the Griggs info. Basically you have to let it roll as it is designed to do that - soft football shaped bushings in the lower arms, stiffer upper bushings, relatively soft springs - allows that to happen stock but it gets all fucked up if someone makes it really stiff and bolts on a panhard without removing the upper links. Anyhow, stock with slightly stiffer bar and springs, it'll roll on corner entry, the rate of roll with decrease and eventually it'll take a set and more or less allow you to drive a line. Pushed really hard it'll settle on the bump stops which is actually a good thing here. But compared to a proper setup, yes it sucks. Proper is not a stock F-body setup either though.

Mustang or F-body, I'd make adjustable spring perches using the stock stuff on all four corners using roundy round stuff. Install as long a panhard rod as you can make (forget most of the off the shelf stuff). Then you've got to build a tri-link. Torque arms are way easier to build and install on these two chassis, but they're heavy, can generate axle hop which will lead to stuff being torn up. Trilink is better but it is extremely hard to package in comparison to the arm, hence why people take the easy road. Stiff front bar (the Griggs bar is one piece they make I like), and stiff springs, way stiff because you have a shitty motion ratio up there, we're at 1950 lbs and could probably stand a bit more, rear springs down around 500 or so but again, effective rate is lower. Tune with some good struts/shocks, spend a lot of time with bump steer, get good adjustability with camber plates and spend time on setup and ride height/centers, and go have fun. The cars can get it done.
 
Its amazing how much the mustang front ends and the 3rd gen f-bodies are so similar. I am at 1800lbs in the front and could use a bit more as well. I have been trying to get a stiffer sway bar, but no one makes anything stiffer than the OE bar for these cars. I have been looking at 3 piece bars intended for nascar, but their standard length is 2.5" to long at 37.5" but i think it might work.

I too have weight jacks on all corners. I believe those are pretty much essential in setting up these cars.
 
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