Width disc brake swaps add??

[Josue]

Might be a vague question, with all the different routes and manufacturers you can use for disc brake swaps, but how much will disc brakes push your wheels further out vs. drums? I know the rotor hats are a bit thicker than where the drums slide over the axles/hubs....

Specifically, I'd like to do a C5 swap on the front of my '68 Firebird, and either LS1 or C5's on the back, still need to research the difference between the two. Does anyone have any first hand knowledge with these on 1st gen F-bodies? I just bought a used set of wheels, and I'm trying to figure out the suspension setup I want/need so my tires aren't buried into the body or something! I keep forgetting that the disc brake swap is something I need to take into consideration with wheel placement too. Getting the wheels first like this, is forcing me to do things a little backwards, but I'm sure someone out there has been through this before...

Thanks!!

[CliffsBlueCamaro]

Someone correct me if I'm wrong, but I believe that the Kore3 C5/C6 brake setups keep the wheels in the stock location?

I went with 12" LS1 brakes front and rear using the swap brackets and hubs from BRP Hotrods. They also advertise that the wheels won't be moved out any, and that was exactly my experience. If anything was moved around at all, it wasn't enough to notice or cause any issues.

What are the specs on the wheels you have (diameter, width, backspacing/offset)?

[Josue]

Well, that would certainly be nice!!

Wheels are 17X8, 235/45/17, and 4 1/2" backspacing on the front. 18X9, 275/35/18, and 5 1/4" backspacing on the rear. I guess with all the bracketry, hub swapping, etc on the front, I'm not sure if it'd even be an issue. On the back though, the rotor would sit right on the axle, right? Seems there wouldn't be a whole lot of room for the rotor to do anything but stick out further than the drum surface?

Mainly, I'm trying to figure out which route to go with my rear end. I need to upgrade my 8.2 BOP 10 bolt w/open 2.56's desperately. Early 70's Nova 8.5 10 bolts are a direct swap, and are 1/2" narrower on each side, which would aid in extra clearance with these wheels. But, I'm wondering if a disc brake swap is going to negate any gains to be had by a narrower rear end?

[alocker]

Usually track width widens on front drum to disk conversions but on the rear they stay the same or very close. Definitely not by 1/2" each side in the rear.

[Josue]

That would be good, glad I went with the 235's instead of 245's up front then.

[Rod]

on my car I run the C5/C6 brake setup in front and a Right Stuff Cadillac brake kit on the rear


from what I have seen most C5/C6 brake setups keep the wheels in the stock location, the rear disc kits usually move the wheel out 1/4 inch each side the rotor hat on most kits, most of the time I have to add longer wheel studs to the factory axles, after market axles have longer studs already

[Josue]

1/4" doesn't seem too bad then.

I was wondering about the studs too. My back wheels are alright right now, but the lug nuts I have on the front have to go. I don't know if the studs are even long enough, there's maybe 1/2" of thread showing, and I can't even get a socket on the lugs well enough to tighten them down.

[alocker]

That would be good, glad I went with the 235's instead of 245's up front then.

This isn't set in stone either. If you use the stock drum hub the difference might not be that much either.

[Apogee]

For most GM short-spindle (GMSS) applications like the 1967-1969 F-body (1964-1972 A-body and 1968-1974 X-body), they use the same flange offset as the factory GMSS drum hubs, so the only difference in track width with such kits is due to the hat thickness difference between the drum (~.10") and the rotor (~.30"). The KORE3 C5/C6 kits therefore increase track width by .20" per side over a drum application. Now if you were converting from factory D52 disc brakes, then it would reduce the track width by .24" per side since the drum hubs and hub/rotors don't have the same track width from the factory.

The rear is simple, as the track width difference is solely related to the hat thickness of the drum (~.10") and rotor (~.24" to ~.28" depending on the rotor), so you're looking at a .14" to .18" increase in width per side.

Tobin
KORE3

[Josue]

So, either way, any width gained is barely worth worrying about then....would that be safe assumption?

[Apogee]

So, either way, any width gained is barely worth worrying about then....would that be safe assumption?

There is no such thing as a "safe assumption" when it comes to fitting tires and wheels under a car IMHO. For some fitments, 3/16" may be the difference between rubbing or now...others it may not matter one bit. The best method is to measure, test fit and final fit the car as it sits, because no two cars are the same. That said, if you intend to aim towards a conservative tire fitment, then you can be a lot faster and looser than if you're trying to squeeze every last millimeter of rubber under there, so use your best judgement.

Tobin
KORE3

[Josue]

Understood!

Thanks for the replies everyone!