I'm ready to upgrade front brakes. I have new 17" zr1 wheels, so I think I should be able to fit these calipers with the 12.8" rotors. In my research I think I decided on the c6 base corvette setup. I found that the front calilers look the same as the XLR and XLR-V but for some reason, the Cadillac calipers are way cheaper. Can someone confirm the calipers and all the parts, slides, bracket, are in fact interchangeable? Anyone used the XLR calipers on their third gens?

Yes, they're interchangeable. In fact, they're exactly the same calipers. But apparently having CORVETTE on them makes them more expensive than having XLR or V1 on them. Also, the XLR is built on the same platform as the C6. XLR = C6, while XLR-V = C6 Z51 (Z51 = Heavy Duty option, or HD). But the calipers are all the same, as are the front calipers on the last two model years of the GTO.

Here's a picture of a NOS V1 caliper in a C6 Z51 bracket on a C6 Z51 13.4" front rotor, mine, from when I was test fitting the various C6 brake options. V1 is the XLR-V caliper. NOS might still be available. XLR calipers are a matte dark grey, while V1 calipers are gloss black. I preferred the appearance of the lesser-descript V1 caliper, as well as the gloss black finish. Just looked more interesting to me and doesn't say CORVETTE.


C6 calipers are the Heavy Duty calipers, PBR's best and strongest dual piston design. While they're exactly the same calipers as on the C6, XLR, XLR-V and GTO, they're also interchangeable with C5 calipers. The differences in the brake options are the sizes of the rotors and pad abutment brackets. The Standard/Base 12.8" front brakes are the same on the C5 and C6, so you need the C5/C6 pad abutment brackets and rotors. You don't want brackets and rotors for the HD option, which = Z51/XLR-V, as those are for 13.4" front brakes, as pictured above.

And, yes, they should fit your 17" wheels. IROCThe5.7L has the same brakes with the new 17" IROC replica wheels. This is his thread, below. Yours, being actual Corvette wheels (or replicas), should also fit.
https://bigbrakeupgrade.com/ - Third Generation F-Body Message Boards

Thanks for all the info. I guess I'm getting confused when people refer to abutment brackets. Are those the cast steel bracket that the actual caliper mounts to, then that bracket bolts to the adapter bracket for the conversion?

So in the end my question is, if i were to get the whole used front caliper assembly pulled off an XLR, the brackets would be wrong and i would have to still buy c6 base brackets mo mount everything up?

So I just did more reading. Sounds like the abutment brackets are the ones that are the black brackets that the caliper floats in, not the adapter brackets.


So would the abutment brackets that come with a take off base XLR caliper be completely interchangeble with base c6 adapter bracket and rotors/pads?

Yes. The calipers are supported by the abutment brackets. The abutment brackets hold the brake pads and bolt to the conversion brackets, and the conversion brackets bolt to the spindles.

And yes, XLR calipers, brackets, pads and rotors are all interchangeable with C6 (and C5) Base brake parts. So if you've got a line on a set of XLR take-offs, then you'll be all set. Just be sure they're really the 12.8" base brakes with the grey XLR calipers (some people might call them black because it's sort of an in-between color, but they specifically have XLR cast into them), not the 13.4" HD brakes with the gloss black V1 calipers (for the XLR-V like in my picture above). But all are the exact same calipers, just with different IDs cast into them: CORVETTE, XLR, V1. And all use the same abutment brackets: one for the C5/C6 Base/XLR 12.8", and one for C6 Z51/XLR-V HD 13.4".

Edit: And you'll need this conversion kit (or the equivalent from your preferred vendor):
C5/C6 Partial Conversion (bigbrakeupgrade.com)

Some people do their own machining of the spindles and hubs, so if you do that yourself, then you'll just need these conversion brackets:
C5/C6 Conversion Brackets (bigbrakeupgrade.com)

Sweet, thanks for all the great info!

To confirm one hopefully last thing, the 05-06 GTO front brake calipers and brackets are identical too, just with no cast branding, right???

Looking more closely the XLR abutment brackets, they do look like they match the C6 ones.

The GTO ones though looks like the calipers match, but the mounting holes in the abutment brackets are positioned differently...

Do I have this correct?

Looks like I do...

GTO VS C6

You keep answering your own questions lol. But that's good. It shows that you're doing your own research, rather just blindly believing what you're being told.

Yes, those GTO calipers are the same but without cast branding. The ID is paint or possibly a decal. So remanufactured calipers for GTO will be plain cast aluminum that can be customized.

Correct, again, the GTO abutment brackets will not work. Only the calipers will. So if you go with GTO calipers, you will still have to use abutment brackets for C5/C6/XLR base brakes.

Caliper guide pins will also have to be correct for C5/C6/XLR abutment brackets. Not sure what, if any, might come with GTO calipers, so be sure to check those too.

In some places I'm seeing all 4 calipers listed for sale. Is there a way to fit the rears on our cars? Is there much of any benefit?

Also, anything I should keep my eyes open for when considering used calipers? Or would it be a better idea to go reman?

Rear disc brakes require a conversion, which involves pulling the axles on each side. But assuming this is for your 91 Z28, then it probably already has the 3rdgen PBR aluminum disc brake system, yes? If so, then they're supposed to be good enough to keep.

Although if you already have those rear disc brakes, then you probably wouldn't be asking such a question. So if you have drums, then there is a drum-to-disc conversion kit for 3rdgens from Ed at flynbye.com and I believe it's for those 3rdgen PBR brakes.

Personally, I like new, NOS calipers, and Rock Auto might still have some for C6 and XLR. But you'll probably only find remans for GTO. And if you're looking for no cast brandings that you can customize with paint and logos, then remans will be your only option.

Regarding used calipers, unless you like rebuilding and cleaning up calipers yourself, which sounds complex and intimidating, but it isn't really, then the simplest thing would be to get remans, as they'll be like brand new. You'd need cores though, or the price will be too high.

So if you can find cheap used calipers, and I mean cheap, under $30 each, which you'll probably only find on ebay, then get them and go from there. If you think they're good as is, no signs of leaks, then clean them up and install them, but that will be your call. Or rebuild and clean them up to your liking. Or just use them as cores toward remanufactured calipers.

Yup, my 91 Z28, does have the original PBR rear discs. Sounds like I'm best to stick with them. There were some listing on ebay that were $10 more to get the rears too. Now i know it's not nessissary.

I'm trying to do this cheaply hence looking for used ones on ebay but the best I'm seeing for the front XLR pair is about 140. (Still way better than twice that for used C6 calipers...) Maybe a used set that I clean up, paint and rebuild if they look like they need it, may be a good option. How often do calipers need rebuilding. Do they just start leaking past the seasomething? point?

Theoretically, calipers should never have to be rebuilt. But IT happens. And if you're installing used, it's not a bad idea, for your own peace of mind, to rebuild them, or use them as cores for new remans.

Here are some decent deals I just found.
A close-out on remanufactured XLR calipers from Rock Auto. No core charges. Gray emulsion coat, sounds like a primer that can be painted over; doubt it's a finished powder coat. Grind the faces smooth of the XLR if you don't want it and paint them to your liking.
More Information for CARDONE 184870 (rockauto.com)
More Information for CARDONE 184871 (rockauto.com)

C5/C6 pad abutment brackets for base brakes. I've purchased from Kore3. I can't verify any experiences with the ebay dealers, but most seem to be legit these days.
KORE3 Industries LLC: On and Off-Road Performance Automotive Components
97-04 C5 Corvette Front Caliper Mounting brackets New GM 12455799 X 2 1997 1998 | eBay
GM OEM Base C6 Corvette and C5 Front Brake Caliper Bracket 88955518 Abutment | eBay

I see several brand new XLR calipers, not remans, on ebay, for reasonable prices, no core charges, but shipping.
Some remans with brackets for reasonable prices also on ebay, no core charges, but high shipping fees.

And I did searches for C6 and GTO products from the same sources, but no better deals than the above products came up. So the XLR products seem to be the most reasonably priced.

So everything is there for you to pick and choose how to assemble your front brakes. Rotors and pads, I'd definitely get NEW though. They're not expensive through auto parts stores, Rock Auto, ebay vendors, etc.

Well after clarifying all this very helpful information, I had @acesena4 point out that we can also put the 4 pot fixed brembro calipers from the base C7 and Caddy ATS with 12.6" rotors on our cars... This option is making me think real hard if I want to peruse that route...

C7 Brembo brakes should perform better, and they'll have that updated, "exotic" appearance. Used products might be difficult to find, but new ones are still available. Such an upgrade will likely come with an "exotic" price tag too.

But projects evolve. And yours seemed to have a moderate budget when it began, shopping for used and remanufactured parts. But if you're willing to pump more into it, then go for the C7 Brembos, and don't look back.

I'm diving into the deep end on this one!!! Just ordered a pair of the ATS (C7 Singray) front 4 pot Brembro Calipers. ($250) so not that much more than the C6 option... and they're brand new, but "may" come with pads and hardware, it was mixed 50/50 with the reviews... They should show up tomorrow so we'll see.

Been talking to Scott at BBU and it sounds like he will be able to come up with the rest of the parts I need to pull it off with my current setup! (just may take a little time, I guess tax return season is a busy one for brake upgrades, lol!

Pads that come with calipers are usually cheap. And if they're anything like OE pads for Corvette brakes, then they'll leave a lot of dust. At least, that's been the complaint about recent generations of Corvette OE pads, maybe because they're geared toward high speeds and stopping power: "track" pads. I'd suggest shopping for the pads of your choice. Hardware will probably come with them.

Scott is the best! Involving him was a good thing.

And someday if you ever decide to upgrade the rear brakes, Scott can probably create/assemble a matching rear brake conversion, if he doesn't already offer one, and I think he does. The parts are still new enough that they'll be available for years to come.

Because even though 3rdgen PBR rear brakes are considered good, or at least, good enough (to keep for now), and certainly much better than the old iron calipers, they really aren't THAT good. It's mainly that special code that makes them so revered by many 3rdgen owners... wait for it... 1LE. It suddenly got really hot in here. Would somebody please turn on the AC?!

Yea, hoping to leave the rears stock for a while and see how the total braking performance is. I may switch out rear rotors though. The current ones are getting a little rusty...

Hey, so, my car is old and the brakes have sucked as long as I can remember, so I ordered a new master cylinder to install while I upgrade the front brakes. I did also install the next higher strength spring in the factory perportioning valve to push more pressure to the rear. That said, with the thirdgen master cylinder intended for non 1LE four wheel disk brakes, will i nhave the needed brake line pressure to make the most of the setup. I havent read much about upgrading the master cylinder to a 1LE variant, or one out of a later model camaro or corvette. Is this even possible? Necessary???

Shouldn't be a need to mess with the master. Some people do, but most people don't. Wait and see. At least you'll have a new one on hand.

Changing the spring might be as good as swapping the master. You'd have probably been fine without it, but since you've already changed it, leave it. It might provide the better balance you feel you've needed.

Or it might not help lol. The jury is still out on the spring mod. That decade-old thread keeps going and going, with thousands and thousands of views, and tens to hundreds of people supposedly having done it, yet very few have reported back, good or bad. Kind of makes a person wonder. But knowing the reputations of the SoCal people who brought the mod to light, they do know their stuff, so I'm inclined to believe it probably can help.

All cars used the same brake master cylinder in your year. There is no 1LE variant, they're all the same. The difference is in the proportioning valve.

The spring mod really does change how the brakes work but the guys in that old thread never understood how it worked. That's why one guy would hardly notice a difference and another guy would almost crash and do a 360 on the highway.

This thread is the one to read, especially the explanation how the prop valve and spring mod works.

https://www.thirdgen.org/forums/brak...ng-torque.html

Wow, great post over there QT.

Thanks!

The C7 (ATS) Brembros are all in, and honestly... they're pretty amazing!!!

Full story can be read here:
ATS (C7 Base) brakes on a 91 Z28 - My Experience - Third Generation F-Body Message Boards