Recently bought this kit...

Ceramic pads vented/drilled rotors.



Problem is the rear brakes are no where near strong enough. Is there an easy way to install a brake distribution valve on your cars? (86 GXL 5 lug) Road race guys? Anyone make a kit?

Thanks

 

put a bigger brake booster and the 4 pot calipers and rotors on the back maybe? I don't think your going to get anymore from the rear brakes than 30% of the total force anyways.

 

Do you have different front/rear pads? The easiest way to adjust brake bias (within reason) is changing pads. Beyond that, you can get adjustable proportioning valves, or go to a dual cylinder racing setup (probably overkill).

How are you determining they're not strong enough? Just feel into corners?

-=Russ=-

 

The fronts do all the work anyway thats why we GXL owners have 4 piston calipers on the front. Fuuk the rears!!

 

The brake bias adjusters that go inline with a brake line can only reduce the total force, so installing one in the rear will only make it worse. Get better pads.

 

I'm using a beefed up auto trans and a turbo setup. I'm trying to get the rear discs to hold the rear tires from spinning to build up boost off the line. What type of pads are best for this?

Also if I were to install a valve reducing the pressure going to the front brakes wouldn't the pressure then have to travel to the rears? Or installing some sort of line lock on the front brakes that would route all my brake pressure to the rears?


My question is where do I install it exactly?

Or could I remove the stock prop. valve and make the hole going to the rear brakes larger?


The car stops great, I could easily stand to loose a bit on the fronts. Can a 4 piston caliper be mounted int he rear?

thanks all...

 

You could use a proportioning valve to adjust the distribution. You could also pull your emergency brake really hard

You don't want to put 4 pots on the rear because your car would become a death trap. It's not safe.

 

Uh...

You don't want to do anything that will dramatically increase the rear braking power that would function on the street as well. That's called a "deathtrap" - lock up the rear brakes while cornering, and the back end WILL come around. In a hurry.

For that matter, if you did something like that and tried to stop after a drag run, there's a good chance you'd lock the rear and swap ends at the end of the quarter mile.

Clear?

From Wikipedia:
This is what you want to look into - some form of transmission or driveshaft brake that won't operate on the street.

-=Russ=-

 

good pads and rotors are enough of an upgrade for brakes as far road racers. If your super hardcore and want to get some good lap times and dont wana worry about brake fade you could opt for big brake kits from wilwood. and get a 2 or 4 piston upgrade in the rear..unfortunatly you wont be able to retain your ebrake and would need a larger master cylinder. If you wana go bigger caliper in the back but retain the ebrake cable find a car with a larger 1 piston caliper rear with ebrake cable, and make a bracket that would fit on the hub and have the corrisponding rotor to go with it.

Even if you upgrade your brakes..NEVER try to change to brake bias unless you absolutely know what your doing.

If your looking for a way to hold boost on a standstill and dont wana use your ebrake you can opt for linelocks.

 

Trans brake is the way to go. You should have no problem then. I think they hook into the valve body and hold the tranny hydraulically somehow.

 

What about with larger 4-piston set up front, and larger master cyl? Would bigger 4 piston in front and say a 13" disc in the front, smaller 4-piston in the back with the stock 11.5"(?) and more pressure holding it all together work on the track? Sorry to thread jack, but its something I've been wondering about for a while.

 

You could probably run that setup if you have a proportioning valve. You need to make sure your front brakes lock up before the rears. You can use a proportioning valve to help make sure your setup has adaquate distribution.

I used to have a bonneville where the rears locked up before the fronts. It wasn't safe in the summer and I almost died a few times in the winter. Nothing wakes you up faster then tapping the brake on snow only to find out the car acts like someone just yanked the ebrake.

I understand what your intentions are with upgrading the setup. But FWIW, the stock 4 pot fronts and single rears are a very good setup, even for track use. If this car is only going to see the track than buy some new rotors and some race pads and I gaurantee you will be amazed at the stopping power. If it is going on the track and the streets then buy an aggressive street pad and call it good. You could dump 3K into a better setup and it won't help you drive to work and home.

Brian

 

That's no true if you set the bias to be more towards the back, compared to the stock bias, which is pretty far forwards, IIRC... (it was also set for the stock tires, which are 20 year-old technology)

By restricting the fluid that goes to the rear brakes, you can give the front brakes more pressure, or visa versa. If you set the bias valve to simply be fully open, the rear brakes would have the same amount of power as the rear.

Also, the stock proportioning valve makes the front bias stronger and stronger the harder you apply the brakes (if I read correctly).

OTOH, when you upgrade to higher grip tires (and a sorted suspension), you'll need more and more front bias due to weight shifting to the front.

I think if you simply use the stock vented rear brakes, with good pads, lines, fluid, and if you need it, a bias controller, it would work fine... the only issue I can imagine would be brake fade, which seems both unlikely and inconsequential when it comes to the rear brakes (if you're braking that hard, most of the weight, and thus the braking ability will be in the front anyway).

If you absolutely must have more braking force in the rear, you could use a bracket and larger diameter rotors... Corksport makes a kid for the vented brake calipers.

 

A t brake would certainly fix the problem. But it's also very expensive.

As far as creating a "death trap" I don't think you all understand what I'm saying. I talking about installing 2 electronicly activated solinoids inline with the front brakes. I'd have these hooked to a button on the steering wheel. Once I was staged and ready to race I would press the button and hold it. Then apply pressure to the brake. As long as the button was held I would be getting all my pressure to the rear brakes. When the light turns green I'd release the button and the brakes and mash the gas.

There would be no "death trap" factor. The cars brakes would operate normally unless teh button was depressed.

 

Cool. I was trying to think of a good way to make the car brake hard at high speed, but I only had figures and guess work in my head. I guess experience owns calculations, thanks

 

No, I'm right. Those inline adjusters will only reduce the force, how could they possibly increase it? You'd need to somehow disable the stock proportionning valve then install an inline one to have it be possible to get more than stock rear bias. Then you could have a couple settings, one for drag launches and one for street.

 

Depending on how much power you're making, you may not be able to get the rear brakes to hold, regardless of braking force.

If you haven't replaced the brake lines, SS lines will help you get more pressure to the brakes (or new rubber lines, they're about the same - both WAY better than old stuff).

But if you have the brake pedal firmly mashed and are still spinning the rears, I don't think disabling the front brakes will help much - right now, to spin them, you need to overcome the brake friction, plus the friction of the wheels against the road (as the front brakes are keeping the car stationary).

With the front brakes disabled, you only have the rear brake force keeping the wheels from spinning. And if they do spin, the car moves.

How much power are you trying to hold?

-=Russ=-

 

If the brakes aren't capable of stopping the rear wheels from turning, then why would you think that reducing the force to the front wheels will make a difference at the rear wheels. While you might not have to press as hard, the ultimate pressure possible is going to be roughly the same. I would say that you need to get better pads. I would recommend something that doesn't need to heat up to stop like race pads, so you would want Hawk HPS pads, or maybe HP+.
Or you could just put on the e-brake. I don't see what the problem with that is.....

Also, assuming that you are talking about doing this on a race track, then the WORST possible thing you can do is alter the brake bias. I realize you are talking about the proportioning valve begin used temporarily, but that won't work the way you are talking about (see above statement). You just need to beef up the entire brake system until it holds. If the pads won't bite, then nothing will help.

 

A lot of misinformation and or wrong assumptions in this thread.

There is more to brake bias than line pressure. Piston diameters come into play as well so just running without the stock bias valve won't work for what he's trying to do.

Black91n/a has it right about the in line aftermarket valves.

A larger master cylinder will lower your caliper pressure, not raise it, for a given foot pressure.

Almost any engine can overcome the rear brakes while the fronts are locked so this is not the solution.

The reason the stock bias cuts the pressure so much is because you need to under heavy braking. With todays tires you might even need to cut it more because of more weight transfer forward with tires with more grip. The rear tires will be even less loaded. I think the stickier tires in back will work more as well so it all evens out.

If you put 4 piston calipers out back you might be able to load up your turbo on the line but you will most certainly lock up the rears as soon as you touch the brake pedal at speed.

Line lock on the front is for burn outs, line lock in the back won't work unless you put huge brakes back there.(see above problem with that)

If you are using a domestic auto tranny a trans brake will be no problem to find, that is the answer to what you are trying to do.

An one final note. The stock brakes with good pads, fluid and brake ducts will stop an FC from 150mph+ over and over again with no problem. If you think you are having trouble, check the three things I listed, that is where your problem is not the system in general.

 

Alright so my theory was shot down and explained. Thanks for that.

I'm trying to hold about 500 WHP so ebrakes not gonna help. Although I do try that. So I'm back to my only options. Get a larger stall converter. Or go with a T-brake. I'm running a built 200r4 so finding parts isn't the problem. The 700 dollars in P/L is the problem....

Appreciate the help guys...

 

Ah, I just saw the part about the grand nash motor in your sig, that explains things. Well, good luck with everything.

 

One of the best oem import setups I know of is the EVO8/ STi Brembo setup. Both use the seperate drum-ebrake setup with a 2 piston caliper but they have serious stopping power.

One of the best oem Domestic setups are from the SRT-8 Charger. They are Brembos and they are freaking massive. I am unsure of the rear setup if they are drum-ebrakes but they are 2 piston rears and they are bigger than the front 5 lug RX-7 brakes.

-Gabe

 

So can you explain why my doesn't work. I know its just an armchair theory, but there are valid reasons for thinking up ways to get the car to brake harder and faster without compromising the susp. geometry. I was asuming that a 50/50 bias, but with larger pistons up front the car would hug the ground as the pedal was depressed. I know the stock brakes work great, and I know you shouldn't fix it if it ain't broke, but I still need to get it through my head.

EDIT: I can describe the car "hugging" the ground. Instead of the front being pushed down and the rear following suit, both front and rear push down, slowing the car. Make sense? Not really, but I can't think of another way to say it.

 

The center of gravity is above the point where the force is being applied (road surface). The car will rock forward - there's no way to avoid that. You can control how much it rocks, but it will load up the front, and unload the rear.

The fundamental problem here is asking rear brakes (which, while decent, aren't as strong as the front brakes, because they don't need to be, and having identical braking power is downright dangerous) to hold 500WHP - even if it's not wound up to that power, if he wants to be spooling the turbos on a big motor, they're going to be trying to hold 200+WHP, probably more.

Transmission brakes were invented for a reason. For those unfamiliar:
http://www.hotrod.com/techarticles/d...ech/index.html

Holding that much power on the starting line is going to be basically impossible to do with the stock brakes, or anything resembling a sane (safe) braking setup.

The solution to your problem is a transmission brake.

-=Russ=-

 

Hench why I keep to try to figure out how why a 50/50 wouldn't be good, or even a 60/40. Weight shift to the front for obvious reasons, but wouldn't you want the rear to still have a much weight on it as possible to prevent the car from spinning out. I feel like I'm losing something in the translation here guys, is it me, or am I explaining in an unclear way.