Hey all, so I'm looking to upgrade the brakes on my 09 Bullitt, specifically trying to upgrade to 4 piston 14 inch rotors upfront from the 08/09 GT500 and the 13/14 GT500 rear brake upgrade to the 13.8 inch rotors in the rear. My question is will I see any negative issues/handling by having almost similar size rotors front and rear.
Brake Upgrade Different Sizes question
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I think it all depends on the ratio between pad to rotor contact areas. In theory if you increase stopping power in the rear you may increase braking distance. But I’m not sure how exactly our abs system works and it may not have any effect at all. I know I have a car I’ve converted from drum to disc in the rear and without a different proportioning valve the rears would lock up early under hard braking.
2008_ScarlettGT
Member
I have the 4 piston up front with the 13/14 rear brakes and I have not noticed any ill braking effects from this setup. To be fair, my car is a streetcar so I don’t push it to the very limit on public roads, but during spirited driving it hasn’t been a problem on my car.
007Stallion
Junior Member
The stock rotors are 11.8”, so using the larger 13.8” rotors in the rear will increase braking torque due to the longer lever which will be increased by 1” (1/2 of the change in diameter) I would assume clamping force would remain relatively unchanged at the rear since the stock caliper is reused. A pad with a higher COF can increase clamping force however.
You will also have increased rotational mass, decreasing acceleration by a small but measurable amount. I doubt it would affect handling and probably nothing the butt dyno would detect.
You will also have increased rotational mass, decreasing acceleration by a small but measurable amount. I doubt it would affect handling and probably nothing the butt dyno would detect.
DieHarder
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Just upgrade the fronts for now and reassess. That's what I did and never found the need to do the rears. Unless you're going to track it upgrading the rear is probably not necessary.
I did the exact set up about 5 yrs ago (Front/Back) and had no problems whatsoever. The stopping power increased by about 20% and they work like normal OEM. You will need at least 18" wheels.
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AHaze
Member
Vorshlag extensively road raced a 2011 GT and used the 4 piston fronts with both rear rotor sizes at different points. I honestly recommend going through the build thread. It's long but IMHO, worth the time if you're even semi serious about making an S197 handle.
Vorshlag 2011 Mustang GT + S197 Development Thread - Vorshlag Motorsports Forum
This forum outlines our major in-house projects that we are currently building or developing
www.vorshlag.com
Hmm I'm curious about that, why's it matter if you cant activate ABS?
That's a good question. Chicken legs? Despite I'm 6'2'' I'm more the marathon runner guy. To be fair it was with the OEM Akebono pads, after that emergency brake on the Autobahn, I changed them to more aggressive EBC Yellow pads (they brake much harder but they ruin the rotors, no recommendation from me).
The 07 doesn't have a brake assistant, so the ABS pump gets not activated from the brake pressure sensor alone, you must step on the pedal so hard that the brake pad friction is higher than the tire-road friction. When the tire stops the wheel sensor activates the ABS system.
I was not able to step hard enough on the pedal to overcome the tire-road friction at 100 MPH and the ABS got activated much later (from 70?).
Hello.
I just bought the Ford performance front GT500 Brembo 4 piston 14 inch uprade kit, waiting to be installed in spring. But I wonder, is it possible and make sense then at least to exchange the 11.8 inch rear rotors with the existing stock front 12.4 inch rotors and front calipers ? Anybody tried this? Adapters needed? Thx in advance
I just bought the Ford performance front GT500 Brembo 4 piston 14 inch uprade kit, waiting to be installed in spring. But I wonder, is it possible and make sense then at least to exchange the 11.8 inch rear rotors with the existing stock front 12.4 inch rotors and front calipers ? Anybody tried this? Adapters needed? Thx in advance
Yes, you need to use 18" rims or larger for them to fit...
I have a complete brand-new conversion kit for sale in the classified section:
www.s197forum.com
You being in Europe might be cost prohibited to ship...
I have a complete brand-new conversion kit for sale in the classified section:
S197 PARTS FOR SALE
More NEW parts... 13-14 Dynamic Friction GT500 13.8" Rear slotted and cross-drilled disc brake R/L rotors $180.00 05-14 Mustang GT to GT500 13.8” Rear brake rotor adapter brackets kit. Must use 18” rims or larger! $100.00 Will take $250.00 for the entire BIG BRAKE KIT!
www.s197forum.com
You being in Europe might be cost prohibited to ship...
Hello. I have even 19 inch 2015 Bullitt wheels. But my question was not about upgrade the rear rotors to gt500 size. I just want to reuse my stock front 12.4 inch rotors and calipers on the rear. So this would work with such adapter brackets?
hello, if you read my previous post, I am installing the genuine Ford performance GT500 Brembo 14 inch set on the front ! I am no expert in front/rear brake quotient maths, but tell me :
serial setup is 12.4 inch front / 11,8 inch rear
my target setup would be:
GT500 upgrade 14 inch front / 12.4 inch to the rear (front brake rotor and calipers relocated)
that does change the front/rear brake quotient unpredictably?
if I dont do it, it will be 14 inch front / serial setup 11.8 inch rear - which is a legal setup,
how about the front/rear brake quotient then ?
DieHarder
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No need to change anything in the rear. Many of us including me run the Brembo's up front with stock rears and everything works fine. Only upgrade to recommend for the rear is steel braided brake lines. Otherwise good to go. Cheapest route for the Brembo's is to purchase new rotors/pads; and rebuilt calipers for a 2008 - 10 GT500 from an auto parts store (I got mine at O'Reilly's). Ran about $400 for everything (expect costs to be somewhat higher now). Mine came in gloss black powdercoat and have worked flawlessly since installation. You can get brembo stickers on feebay.
Piston size bigger, pad size bigger, friction coefficient unknown, aber mach doch!
Oh, no e-brake, good luck with TÜV
helloo, thanx al lot, I think I will not touch the rear. my concern was mostly the looks, because from 17" to 19", the small rear rotors might look a bit ridiculous in that huge wheels ...
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