last one...
Left: GT500 13.8" rotor and caliper installed. Right: The OEM rear discs are 11.8" in diameter and use the same caliper and brake pad
The 2014 GT500's brake components are becoming popular upgrades on the various Mustang forums. The 2014 GT500's front 15" 6-piston brakes are a bit extreme, and most of the draw is to the hard parking crowd, for the Big Brake/6-piston looks. Hey, I get it - looks cool, but very few racers have moved up from the 14" brakes to 15" brakes. Some of the Pro teams and endurance cars, sure, but not the club racers or Time Trial guys. What intrigued me more was the fact that the 2013 model GT500 got a
big bump up in rear rotor size, from 11.8" up to 13.8", so we went with this upgrade first. Why? Because we were seeing problems in the rear, not the front, and this upgrade is fairly substantial for a very modest cost.
Left: GT500 13.8" rear rotor is 16 pounds. Right: The 11.8" rotor it replaces was only 12.5 pounds
We searched high and low and have rounded up the OEM GT500 13.8" rear rotors, the taller caliper brackets, and even the "GT500" calipers. The weights for these parts vs the 11.8" parts are shown here. Note where all of the added weight is - almost all of it is in the rotor. And the GT500 caliper? It is identical to the '11-up Mustang caliper, and even superceeds the 2005-2010 GT rear calipers. That is something we found after digging and testing, but Ford says this shouldn't be. They will have to revise their books, because the '11-up GT rear caliper is identical, from the casting numbers to the final machined part.
Left: The taller caliper bracket for the 13.8" brakes is 5.3 pounds. Right: The caliper bracket + support for the 11.8" brake = 4.84 pounds.
The 2" larger diameter GT500 rear rotor is almost 3.5 pounds heavier than the old 11.8" rotor it replaced, but my pic above was a very worn rear rotor (which had lost about a pound of metal), so it really only went up about 2.5 pounds. This is added metal that can
absorb and shed heat, which isn't a bad thing. The taller caliper racket is almost a wash, with the GT500 version being about a half pound heavier than the shorter GT version. One thing to note is the GT's 11.8" rear caliper bracket has an axillary support bracket that clamps around the axle tube and adds some lateral support. This extra bracket doesn't exist on the GT500.
Left: The GT500 caliper is the same unit as the GT. Right: The rear dust shield for the smaller GT brakes
We went ahead and kept the "GT500" caliper we bought and used it on our 2011 Mustang, mostly because our old calipers were looking a bit worn and crusty. Ford insisted these were different calipers, but that just was not the case. We did another GT500 13.8" rear brake upgrade on a 2012 GT a week later and re-used the guy's old OEM calipers, which were identical so they fit identically. There is no dust shield for the 13.8" GT500 brakes, so the old one is removed (doesn't weigh much). The old brake lines worked on the new caliper location, too.
13.8" rotor installed with the old 11.8" rotor slide over the lugs, for scale
All told we added about 3 pounds per side on the 13.8" rear brake upgrade, compared to the brand new weights of the 11.8" disc brake parts. That's not bad for a TWO INCH upgrade in rear rotor diameter. This increase in diameter will increase rear braking torque, the added rotor mass will add more surface area and should help with rear brake cooling, and we hoped the ABS system can keep the braking balance in shape on track (it did).
The hardest part of the swap was pulling the axles out of the housing to be able to change out the caliper brackets. Not hard really, just messy. So you will need to replace the diff fluid and re-seal the diff cover if you plan on doing this rear brake swap. Since the axles have to come out it is a great time to upgrade the rear wheel studs (ARP 3" long rear S197 studs), but these technically can be done on the car (it is just more of a PITA). Also check your outer axle seals for melting/wear. Ours had been replaced earlier this year, so it all went back together and was about a 2 hour job, start to finish. We will go back and make/add rear brake ducting for this car soon, too.
Left: These larger 13.8" Rear brakes fill out the inside of the 18" wheels on our 2011 GT. Right: Same brakes on a 2012 GT with stock 19" wheels
After the new 18x12" wheels were fitted, new springs were in, front fenders were on and trimmed, the rear brakes were upgraded, axles were back in and diff fluid changed, the ride heights were finally squared away and the car re-corner balanced. Damn... this car is heavy.
We brought both R6 and A6 compounds of mounted Hoosiers to Hallett, a first for us
Another planned change for our TT3 car from all previous NASA events for 2013 was the switch from Hoosier A6 to R6 compound. The A6 tires just don't last very long on this heavy car, and we were hoping the R6 tires would be a better compound to test with. This is helpful when we go to the NASA events early and run the Friday Test-n-Tune, on tracks where we don't know the layout (driver training) or if we have had significant changes to the car since we ran here last (always!). The longer wearing R6 would help Amy and I learn this brand new (to us) track layout, but we didn't get wrapped up with the car in time to go to the Friday testing, so we had to learn the layout on race day. And then I broke the car almost immediately on Saturday... long story, tune in next time to hear more!
So the Hoosier A6 tire is terrible for track use. TERRIBLE. I wouldn't do it if this tire was penalized like the non-DOT racing slicks (it should be), but this is part of the TT Arms Race, so I keep bringing them. The A6 is
very heat sensitive and after 1 hot lap on our car it has been falling off about 1 second per lap, and after 3 laps they are just a greasy mess. It has gotten to where I have to get in my best lap on my first lap, usually in the first (coolest) session, and I've stopped even scrubbing the tires at all on the warm-up/out lap. The R6 should be a lot more forgiving with regards to heat, we have nothing but hot months of racing and testing ahead, and I didn't know the next track on the schedule (Hallett) at ALL. The R6s went on the new 18x12" set and a set of worn A6s went on the older 18x11/18x12" set of wheels... but hopefully we wouldn't need them, and that set could stay in the trailer this weekend. I told my guys here that I'd only mount them if I was getting beat, heh.
Our shop was slammed that week so the guys handled all of this 12" wheel/fender/brake prep work on our 2011 GT in about a day and a half, in between customer jobs. Our service workload has gotten pretty heavy of late - so much so that I've hired a third technician to help, who starts this week. We had no less than 7 Mustangs at the shop one day last week, along with the regular BMWs, Subarus, Miatas, Corvettes and LS1 swap. I've been busy looking at bigger buildings to move us into, and will update this thread after we find the right place.
Gotta stop it here. More soon,