Larger Rear Brake Rotors?

[VoodooBoss]

I've decided to stick with the stock size rear rotors for now. If I was going to change them I'd go with the Steeda which is in-between the stock and GT500 rear rotor size at 13". Thanks for everyone's comments.

 

[Jimmy Pribble]

I've decided to stick with the stock size rear rotors for now. If I was going to change them I'd go with the Steeda which is in-between the stock and GT500 rear rotor size at 13". Thanks for everyone's comments.

Wait a minute; I ain't done yet.

I also agree with Grant's point about bias. However, if the same rear brakes are to be found on the standard GT and the Brembo/Boss, wouldn't a rear upgrade just restore the bias found on the standard GT? Was the bias incorrect and then corrected with big brakes up front? That seems unlikely to me. Either way, it can't be the same. One is better than the other. Obviously, I don't expect it to be perfect; just speaking in general terms. Also, just trying to get the bias in the ballpark. The ABS takes care of the rest.

Thoughts?

 

[VoodooBoss]

Wait a minute; I ain't done yet.

I also agree with Grant's point about bias. However, if the same rear brakes are to be found on the standard GT and the Brembo/Boss, wouldn't a rear upgrade just restore the bias found on the standard GT? Was the bias incorrect and then corrected with big brakes up front? That seems unlikely to me. Either way, it can't be the same. One is better than the other. Obviously, I don't expect it to be perfect; just speaking in general terms. Also, just trying to get the bias in the ballpark. The ABS takes care of the rest.

Thoughts?

There's plenty of first hand experience using a 13.8 or 14" rear rotor with a 14" front rotor with no issues. I guy I have done many track days with has the BAER 14" kit front and rear and he has noticed no difference. When I'm behind him coming down from 120 mph into a 40 mph corner his car is stable. It's the hardest braking zone of the tracks here in NorCal. The Steeda kit splits the difference and looks to be a safe bet. Plus the costs is similar to the GT500 rear setup including replacement rotors. When my current DBA 4000 T3 rear rotors need replacing I'll revisit this.

 

[travelers]

I have a GT that I plan on upgrading to the stock Brembo 4 piston calipers (14 rotors) this spring. I also have the Shelby 13.8 rotors and brackets for the rear. I am going to try and get to the NJ motor sports park this spring or summer. Most of my driving is on the street and it's not a daily driver, although its a lot more fun driving then my pickup.

I have also read that with the upgrade some people have experienced a harder peddle. I know there is a difference in the brake boosters between the GT and the Boss/Brembo package. I already have the upgraded booster also along with SS brake hoses.

With reading all the comments, I'm thinking of doing the front brakes first and see how it works and then the back upgrade. There is also the Boss 302S/R upgrade ABS module.

 

[Grant 302]

Wait a minute; I ain't done yet.

I also agree with Grant's point about bias. However, if the same rear brakes are to be found on the standard GT and the Brembo/Boss, wouldn't a rear upgrade just restore the bias found on the standard GT? Was the bias incorrect and then corrected with big brakes up front? That seems unlikely to me. Either way, it can't be the same. One is better than the other. Obviously, I don't expect it to be perfect; just speaking in general terms. Also, just trying to get the bias in the ballpark. The ABS takes care of the rest.

Thoughts?

Restore the bias? No. Considering the specific braking dynamics and geometry of only stock cars...then maybe 'corrected with big brakes up front' is the best/right answer. It's hard to judge from crazy instability under hard braking with my Brembo GT when stock. The stock Boss was always more composed. Most of the brake hardware is the same but the Boss is another 1/2" lower in the front.

But given that many or most of us are lowered and have geometry adjustments like LCA brackets, then the generalizations are a crapshoot at best. Testing and examples from similarly setup cars would be the best info. For my GT, with rear 'brake squat' via the LCA brackets, I am sure that I can greatly increase the rear brake torque. That is, until my stock rubber bushings give up and cause hopping! : Doesn't mean I'm rushing to find out where that limit is. I know that under trail braking, I can still push the fronts. So there's some 'proven' capacity for increasing rear brake torque on my setup.

One more point... increasing braking in front does not always mean ability to increase braking in the rear. For example, if there is a lot of weight transfer, increasing front braking can cause the need to reduce the rear braking. Think circle of traction separately for the front and rear. Now only if we had a volunteer to put a big brake setup on a Boss with stock suspension! (please don't do it)

 

[ufnavy06]

Sooooo general consensus is bigger rear brakes not necessarily good. Spend money on more aggressive pads and heat dissipation. Got it.

 

[VoodooBoss]

Sooooo general consensus is bigger rear brakes not necessarily good. Spend money on more aggressive pads and heat dissipation. Got it.

The point of the larger rotors, whether it's rear or front, is improved heat dissipation.

 

[neema]

FWIW, my rear rotor temperatures are always 50-100 degrees higher than my fronts when I'm done with a session (Carbotech XP12 front, XP10 rear; FRPP brake ducting). I realize there may be a change in brake bias from using a larger rear rotor, but I would offset that with brake pad compound.

 

[further]

One tiny thing I've done which may or may not make a difference, in addition to removing the brake shields, is to remove the small gravel blocker in the front of the rear wheel well, hoping to improve airflow to rotor. TC off would certainly help, as it engages brakes to center the car, but I'm not that adventurous.

 

[VoodooBoss]

One tiny thing I've done which may or may not make a difference, in addition to removing the brake shields, is to remove the small gravel blocker in the front of the rear wheel well, hoping to improve airflow to rotor. TC off would certainly help, as it engages brakes to center the car, but I'm not that adventurous.

I was like you a couple of years ago when Gary and Pete kept telling me that turning the TC off will not only allow you to go faster but you'll have more control over the car on track. I finally got the balls to turn it off and have never looked back and you know what? They were right. ;D Earlier this year I accidentally left the TC on for a session and when I pulled into the pits the rear rotors were smoking.

Pete has also noticed more heat in his rear rotors. I'll be checking that more carefully at track days in 2014.

 

[cloud9]

One tiny thing I've done which may or may not make a difference, in addition to removing the brake shields, is to remove the small gravel blocker in the front of the rear wheel well, hoping to improve airflow to rotor. TC off would certainly help, as it engages brakes to center the car, but I'm not that adventurous.

If you still have side pipes with the discs removed, you don't have to remove those because with enough track time you'll just melt them off!

 

[ufnavy06]

Speaking of temperatures in the rotors, what infrared/thermal imaging gun are you using to check the temps? I'd definitely like to pick one of those up.

 

[cloud9]

Speaking of temperatures in the rotors, what infrared/thermal imaging gun are you using to check the temps? I'd definitely like to pick one of those up.

I have a Longacre with a separate attached probe for checking tire temps as well.

 

[ufnavy06]

Not one of those $300 ones that compensate for pressure differences though, right?

Sent from my SCH-I605 using Tapatalk

 

[cloud9]

Not one of those $300 ones that compensate for pressure differences though, right?

Sent from my SCH-I605 using Tapatalk

This is the one I have from Longacre. I'm not sure where I bought it but they list it on their site for $219.90

http://www.longacreracing.com/catalog/item.asp?id=1314&catid=7

 

[further]

If you still have side pipes with the discs removed, you don't have to remove those because with enough track time you'll just melt them off!

Haha, yeah, one of them was partially melted. I am going to keep the side pipes, it's a measly 11 lbs for that rich sound.

 

[further]

I was like you a couple of years ago when Gary and Pete kept telling me that turning the TC off will not only allow you to go faster but you'll have more control over the car on track. I finally got the balls to turn it off and have never looked back and you know what? They were right. ;D Earlier this year I accidentally left the TC on for a session and when I pulled into the pits the rear rotors were smoking.

Pete has also noticed more heat in his rear rotors. I'll be checking that more carefully at track days in 2014.

I am with you on that. Now that I finally have a roll bar, I am going that route when it gets warm. Just little bites at first, then working my way up. I really feel it at turn one and Hogpen at VIR.

The TC and rear rotor heat is a very real consequence. My stock rear rotors were the first to go, rubbed down to a wafer thin hot plate. I even melted one of my rear ABS sensors. I always have a spare now, in the event of a crack.

 

[jim woodruff]

Rick,

I ordered the Baer kit through Chicane23 (www.chicane23.com); ask for John. I also installed the Baer front 2-piece/slotted rotors at the same time. They were both shipped direct from Baer.

You can also get them from Kenny Brown.

http://store.kennybrown.com/product/brake-rotors/baer-eradispeed2-rear-rotors-2005-2014-mustang-boss-302-and-shelby-gt500

r
Eric

It is my understanding that Performance Friction is offering a rear brake rotor up grade kit also where you do not need to pull the rear axles. Does anyone know about this kit or have any information?

 

[VoodooBoss]

Stoptech has a bunch of good tech articles and here's one on rear rotor size.

http://www.stoptech.com/technical-support/technical-white-papers/rear-brake-upgrades

http://www.stoptech.com/technical-support/technical-white-papers

 

[ls110]

Stoptech has a bunch of good tech articles and here's one on rear rotor size.

http://www.stoptech.com/technical-support/technical-white-papers/rear-brake-upgrades

http://www.stoptech.com/technical-support/technical-white-papers

Great articles Rick. Thanks for posting them!