DPE

Tried a couple different forums and Google and could not find this info. Anyone know the piston diameter of the OEM front calipers? And I assume the pistons are the same size? Sometimes they stagger sizes, but I have not seen that done on a simple OEM 2-pot. Looking at some BBKs for my 2010 GT, but want to make sure they keep the system relatively balanced front to rear. Seems like Stoptech is the only company who overtly pays attention to this.

Phil
2010 GT

Sleeper_08

Note that the GT500s with the Brembo brakes use the same size rear calipers as the GT.

Why do you want a BBK?

What are you planning to do with your car?

Remember - brakes don't stop cars - tires do and your stock brakes will easily kick in the ABS.

There are some very good threads about BBKs in this forum. Have you done a search?

Welcome to the group.

DPE

I'm the same guy who posted the thread asking if the S197 has any major vices on track. In that thread, I was advised to get a BBK given my prior track experience . And honestly I pretty well knew that already; 12.5" rotors on a 315hp, 3500lb car just aren't going to be a big enough heat sink for someone hard on brakes.

I've searched quite a lot. The GT500 Brembos seem like the obvious choice given they should keep everything pretty well factory as far as front to rear balance and such. My only qualm with them is that they require mostly very wide wheels for clearance.

Stoptech I already trust to keep the system balanced properly, but it's always good to do your own homework anyway. And presumably Stoptech will also require similarly wide wheels, given the similarity of the caliper design.

Baer is the wildcard. They use that PBR 2-pot from the Vette that sticks out far less than a Brembo or Stoptech toward the spokes. Might have a chance at still using my OEM 19s, which would be nice. Got the template from Baer, just need to put it on cardboard and cut it out later this weekend to see if it fits.

My concern is that even if it does fit, if Baer uses the same-sized or larger pistons than OEM, that combined with a larger rotor (by 1.5") will significantly bias the system forwards. Yeah, the car has ABS so it's not necessarily a safety concern, but if the fronts take on even more of the work then it'll somewhat defeat the purpose of getting a BBK. And the other wrinkle will be if it can be compensated for by that 13" Steeda rear kit that uses the factory calipers. I wouldn't object to doing that if it kept the balance proper.

Anyway, more than anyone cared to know, but if I can find out the OEM piston sizes up front and find out the piston sizes in the PBR/Baer caliper (which I think are 40.5mm, but not 100% sure on that), I can calculate how much the bias will move forward (if it does) with the Baer kit.

Phil

Philostang

Hey Phil,

Just a heads up, the Stoptech ST40 calipers are not as wide as the Brembos (off the top of my head, I can't speak to the ST60 calipers, if that was what you had your eyes on). Those Brembos are insanely wide! You'll have a bit more wheel options going with the ST40s, but I suspect not a ton more.

As for the need for a bbk, there's quite a bit of controversy here. If you're seasoned, then it starts to make much more sense...that is, if you plan on tracking the car more than half a dozen times this year AND if you are going straight to R-comps. If not, I suspect most of the real angst the experienced guys feel with the OEM system won't be much of a serious issue.

Sure, you'll go through rotors faster, but take-offs are cheap as hell compared to anything for a bbk. That also frees you up to use about as aggressive and resilient a pad as you please (like Hawk DTC-60s or 70s - though I've heard some folks not like the 70s as much in the OEM calipers). So you're not going to go through tons of sets of pads either. Motul fluid will survive with good upkeep. Standard bleeding before the event should suffice, unless you're really hard on the brakes, and then bleeding both mornings should do it (I know SGD was known to bleed at lunch as well, but he was pretty fanatical about it...and damn hard on his brakes). Cooling ducts should be mandatory at your level, and you can fabricate them pretty easily if you're inclined.

Obviously, all that gets real old real fast if you're heading out more than half a dozen times this year. But I don't know, not a biggie to me if you're doing it a few times (to each his own I guess).

I have my set of OEM calipers somewhere in the other garage; I'll see if I can find them and measure the pistons for you. Give me a few days if you can wait.

Best,
-j

chrumck

Yes, they are the same size

chrumck

Just measured them, 41.5mm

DPE

Thanks fellas! That was fast! Good info to have.

Philostang, I was thinking of the basic ST-40 kit. Might even go 1-piece rotors given the price differential between them and the kit with the 2-piece rotors. Glad to hear they are a bit narrower than the Brembos (or are at least positioned in such a way as to not be AS hard to fit wheels over. At least that pretty well confirms they'll fit anything that'll fit Brembos.

This year I suspect I'll be in the range of 5-8 events. And this year I will almost certainly be running on OEM brakes. Just bought the car last week; can't go too crazy throwing cash at it already. Planning on Motul, ducts, and Carbotech XP10s at all four corners. Tried DTC-60s before and they are great, but for whatever reason I like the feel of Carbotechs better. Had a pretty good relationship with Carbotech back when I sold parts for a living, so that doesn't hurt. Anyway, more just planning ahead on a BBK for next year because I'm pretty confident I'll want one. And since I'll need track wheels and tires this year, I'll need to know what BBK I'm likely to go witih so I can buy wheels that fit over my chosen BBK even if I'm not running it this year.

Won't go R-comps this year either, and anticipate I'll be running something like NT-05s or the like in the future. Might even go with a cheapie summer tire this year just to get my feet wet in what to me is a totally different car. Only RWD car I've driven on track at length is an RX-8, and needless to say it has a bit of a different feel to it than the Mustang .

Anyway, I'll hopefully get a chance to pull a wheel off tomorrow and see if the Baer kit will fit my OEM 19s, and do the math to see how much it's going to bias the system forwards. Given slightly smaller pistons, it may not be too awfully much. Of course, if it doesn't clear my OEM 19s, then I'll almost surely go Brembo or Stoptech anyway since 2 sets of new wheels will eventually be in the cards. Thanks again.

Phil