Bigger brakes ...bigger master brake cylinder?

denniskgb · Dec 19, 2012

Need a little bit of help. :dunno:

I had a big brake kit installed on my 02 GTS (purchased from Vapair Performance) srt10 14" rotors and srt10 front calipers all around. Now my question is since everything is way bigger than the doctor prescribed when i left the factory, do you need to upgrade your master brake cylinder to balace the combination?
Any ideas and thoughts would be appreciated. thank you. dennis

scottmarston · Dec 19, 2012

Have you tried them out with your current setup yet? Maybe this will help once you try it out :dunno:

(if it isn't working right, that is)

http://www.outlawdiscbrakes.com/faq.html

denniskgb · Dec 19, 2012

Yes i am currently braking them in. Seems like they are biting better and better. Just waiting for longer studs in the rear and thiker spacers to move the caliper away (have stock wheels).

GTS-R 001 · Dec 19, 2012

Dennis,

The stock master should be fine, it works fine for everyone else with the upgrade, you should find that your stopping distance is about 20 feet less at least now.

I have some extended neck lug nuts if you want to forgo the longer studs

denniskgb · Dec 19, 2012

GTS-R 001 said:
Dennis,

The stock master should be fine, it works fine for everyone else with the upgrade, you should find that your stopping distance is about 20 feet less at least now.

I have some extended neck lug nuts if you want to forgo the longer studs

steve just erased my message since we already talked on the phone. will pm you for emergency brake kit. thank you for your help.

dave6666 · Dec 19, 2012

I have the 14" SRT brakes front and rear on my '01 with the factory master cylinder. No issues.

vancouver-gts · Dec 19, 2012

denniskgb said:
Yes i am currently braking them in. Seems like they are biting better and better. Just waiting for longer studs in the rear and thiker spacers to move the caliper away (have stock wheels).

I have the DBB kit on my 99 GTS with 03 srT 14" calipers and rotors. The DBB kit requires 14" front rotors all corners but the rear caliper, albeit physically the same size as the front , the pistons in it are smaller in diameter. The 5/16 spacers are fine for the front, get the 3/8 spacers for the rear to get the proper gap between the spokes and caliper. You may find too much rear bias now with the bigger rear calipers, so watch for the rear during heavy braking! I've shortened the spring coil by coil in the proportioning valve to find balance without locking up front or rear. Didn't want to use an adjustable PV since it's illegal on the street here and case of a mishap, insurance comp would find the added valve during investigation.
What stops the car better is the bigger rotor diameter and larger pad clamping area.

gutterworks129 · Dec 19, 2012

Make sure you bleed them and it is a night/day difference. I will up grade again if I buy another GTS. I installed a proportional valve on my set up(1996 GTS).

GTLaser · Dec 19, 2012

dave6666 said:
I have the 14" SRT brakes front and rear on my '01 with the factory master cylinder. No issues.

Same here, no issues and it's a different braking machine.

denniskgb · Dec 19, 2012

vancouver-gts said:
I have the DBB kit on my 99 GTS with 03 srT 14" calipers and rotors. The DBB kit requires 14" front rotors all corners but the rear caliper, albeit physically the same size as the front , the pistons in it are smaller in diameter. The 5/16 spacers are fine for the front, get the 3/8 spacers for the rear to get the proper gap between the spokes and caliper. You may find too much rear bias now with the bigger rear calipers, so watch for the rear during heavy braking! I've shortened the spring coil by coil in the proportioning valve to find balance without locking up front or rear. Didn't want to use an adjustable PV since it's illegal on the street here and case of a mishap, insurance comp would find the added valve during investigation.
What stops the car better is the bigger rotor diameter and larger pad clamping area.

I have abs brakes on my model year (2002). would that make any difference? also definitely going bigger spacer, i believe it is 3/8, just waiting for longer studs to arrive. the space now with 5/16 are fine like you said in the front ....the back however, is credit card thin.

denniskgb · Dec 19, 2012

gutterworks129 said:
Make sure you bleed them and it is a night/day difference. I will up grade again if I buy another GTS. I installed a proportional valve on my set up(1996 GTS).

definitely the brakes were bled when they were installed. thank you

Allan · Dec 19, 2012

I think as it's been said, that most guys have no problem with the stock master cylinder. I've seen a few gen II's at the track with the gen III brakes and stock master cyl with no problems.

steve911 · Dec 19, 2012

But on the other hand, I believe that there are just as many who have converted to the gen3/4 Master Cyl. The reason being is that the Gen 3/4 Master puts out more volume pers troke thatn the Gen 2 one. With bigger calipers in all four corners after a brake upgrade, there is more surface area that needs brake fluid to make it work the best that it can. Remember you went from a single piston rear caliper to a 4 piston caliper

dave6666 · Dec 20, 2012

steve911 said:
But on the other hand, I believe that there are just as many who have converted to the gen3/4 Master Cyl. The reason being is that the Gen 3/4 Master puts out more volume pers troke thatn the Gen 2 one. With bigger calipers in all four corners after a brake upgrade, there is more surface area that needs brake fluid to make it work the best that it can. Remember you went from a single piston rear caliper to a 4 piston caliper

You have to at the same time remember some of the basic principles of hydraulics. Like a bigger piston in the master cylinder means more force required to move the same amount of fluid. But less stroke. Out to the calipers, more and bigger pistons takes more fluid but given the same fluid pressure, generates more clamping or braking force. Throw in the booster, line sizes and any other balancing devises, and you have your braking package.

So, changing the master cylinder to a bigger piston size will alter the pedal force and stroke, in theory. I've never driven a Gen 2 BBK car with a Gen 3/4 master cylinder, but I do know with my Gen 2 BBK car with Gen 2 master cylinder, the pedal feel and stroke is just fine, and honestly I can't remember it being any different than before the BBK.

denniskgb · Dec 20, 2012

Thank you all for your responses. I guess you just saved me some $$$$$$ :2tu:

merry x mas to all

Green Viper · Dec 20, 2012

I have the same thing on my GTS, including ABS from a wrecked 02. I have also added the Gen 3 master cylinder and brake proportioning valve and honestly not sure if the bigger cylinder made any difference at all.

The only thing you might want to look at is on my GTS there was a "ball bearing" in the lower part of the master cylinder to help prevent rear wheel lock-up by adjusting the bias, if you remove that and add a brake bias controller (simple and inexpensive) then you will be surprised how much rear brake you can use! Not sure if they took out this when they added factory ABS in 2001/2002 but I can tell you that removing it did make a huge difference on my car.

Rickman6 · Dec 20, 2012

my stopping power comes from the following setup:
front 15 inch stoptech race discs with srt 10 calipers Pf 01 pads
rear 14 inch stoptech race discs with srt 10 calipers standard brembo pads rear...braided hoses allround , competition coupe wheels ,
race brake fluid. stock master brake cylinder..cooling ducts..
the only thing neeeded to create the correct brake bias was the pads...started of with Pf 06 pads rear but locked up ..changed to stock pads rear...issue solved...and of course the difference in rotor diameter front / rear...
99% track car...i.e runs hard and on Toyo R888 / slicks... no heat - fading issues whatso ever...it stops like throwing out an anchor...

SoCal Rebell · Dec 20, 2012

I went with the 14.2" Stoptech 4 wheel BB system on my 2000, original master cylinder works great no proportional valve needed, braided brake lines all around, Brakeman 3 track pads, Castrol SRF high wet temp brake fluid, I bleed my brakes after every track day.

denniskgb · Dec 20, 2012

Green Viper said:
I have the same thing on my GTS, including ABS from a wrecked 02. I have also added the Gen 3 master cylinder and brake proportioning valve and honestly not sure if the bigger cylinder made any difference at all.

The only thing you might want to look at is on my GTS there was a "ball bearing" in the lower part of the master cylinder to help prevent rear wheel lock-up by adjusting the bias, if you remove that and add a brake bias controller (simple and inexpensive) then you will be surprised how much rear brake you can use! Not sure if they took out this when they added factory ABS in 2001/2002 but I can tell you that removing it did make a huge difference on my car.

i will look into that. thank you

GTS Dean · Dec 26, 2012

It takes very little fluid volume to operate the pistons in the calipers during normal braking. If you have moisture in the fluid, or air in the system, you could run into volume shortage if either case is severe.

The main reason for large reservoirs is to make sure you have plenty of brake fluid behind the pistons as all the pads wear down to zero. The more pistons you have, the more fluid volume required to cover wear.

On very large piston area racecars without power boosters, pedal ratio and MC piston area/volume displacement become very critical.

dave6666 · Dec 27, 2012

GTS Dean said:
It takes very little fluid volume to operate the pistons in the calipers during normal braking. If you have moisture in the fluid, or air in the system, you could run into volume shortage if either case is severe.

The main reason for large reservoirs is to make sure you have plenty of brake fluid behind the pistons as all the pads wear down to zero. The more pistons you have, the more fluid volume required to cover wear.

On very large piston area racecars without power boosters, pedal ratio and MC piston area/volume displacement become very critical.

But is the reason someone would want to change to the Gen 3 m/c for the size of the reservoir, or the bore/stroke of the pump?

GTS Dean · Dec 27, 2012

I don't know. You'd have to check the manual. Early Gen II MC has 27mm bore x 32mm stroke. Front/rear displacement split = 65:35 %. The later cars have ABS, Gen III/IV have 4 piston rear calipers and likely have different engineering requirements.

opnwide · Mar 3, 2013

I upgraded to front GTS calipers all around on my car, not the larger srt calipers. I am still using factory '97 MC. I bought a new SRT 2003 MC due to the extra volume, but I never had to install it. The bigger SRT unit will likely make my pedal more hard and possibly harder to modulate. However, if you have the SRT calipers all around, your situation may require something with more volume. It makes sense to use what Dodge intended.

Bigger brakes ...bigger master brake cylinder?

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