IRS, 13inch Rear Brake and 17inch fr500 wheels

[wantscobra]

Apologies ahead of time for my very probable lack of quick responses. I wasn't even sure that I still had an account here after 13 years of not logging in, but here we are.

This April, my long time dream finally arrived. It is a complete kit with IRS. I ordered the rear center section, knuckles and rear brakes from a 3rd party, who did in fact send me what I ordered.

I have been very slowly making progress on my inventory - that's a whole different story - and started working on the front and rear suspension. I am just about to be ready to install my center section and the rest of the rear suspension, and I am now looking at ordering my wheels and tires.

My "plan" was to order a set of 17 x 9/10.5 inch FR500 wheels from a fairly well known outlet for mustang parts. When I ordered my rear end parts, I got 2018 knuckles and 2021 rear brakes from a GT. In my research this week, I have come to the realization that not all mustang rear brakes were created equal (which I should have known), and that the 2021 GT brakes are 13" while the ecoboost or v6 would have been 12.6". This has let me to question whether or not my planned 17 inch wheels will fit over the calipers. I'm not against modifying the caliper a little, but I also don't want to have issues.

Anyone running this particular combination, or something close to it? I've seen a couple of posts here and there about calipers rubbing 17" wheels, and I want to understand what I'm getting into before I spend the money on wheels/tires.

-m

[Lidodrip]

I have the same 13" GT brakes and IRS, but I am using the FFR 17 x 9/10.5 wheels (not sure how they compare to the FR500 wheels). The wheels did rub on the calipers and I had grind down a small portion of the ridge on the caliper. It wasn't a big deal, but I kicked myself for not checking fitment before I powder coated the brakes. Had to re-powder coat, but all is well now.

Caliper modification:



Finished product:



James

[wantscobra]

Thanks. That does help. No worries about the strength of the caliper or anything with your mods I take it?

Your work looks pretty good from here. I don't plan to powder coat. I'm either going with silver or black high temp paint I think.

[Lidodrip]

Because it was already powder coated, it looks like I took off more material than I actually did. I probably took off about an 1/8" of the corner edge and a little more than that off the leading edge of the two raised support bars that sit proud of the caliper body. Since these calipers are designed for much heavier cars and breaking forces, I doubt there is any significant structural compromise after modifying. The only other consideration is that you might be limited in where one can put wheel weights when balancing. I can't put stick on wheel weights on the inside of the wheel where the caliper sits. This was not a big deal because my wheels balanced out fine with weights on the inboard wheel lip, opposite of where the caliper is located.

You might want to consider powder coating. It was fun to learn and I think you end up with a better finish. It has been surprisingly resistant/durable to brake fluid which I suspect would take paint off quickly. The only downside of powder coating is that you have to completely take the caliper apart in order to bake it in the oven. Not a big task, but getting one of the retaining spring clips in can be tricky when re-assembling (until you figure out the technique). I have found having a small powder coat setup has been tremendously useful, particularly with all the small FFR parts (hinges, brackets, etc.).

James

[wantscobra]

That's a fair point. i hadn't really yet thought about the finishing of the trunk hinges and other things that are currently bare steel.

My current body plans are to paint Brittany Blue with white (unknown which white currently) stripes. I ordered my roll bars bare metal and I am planning to paint them the stripe color. Now, I am thinking about painting all of my hinges and other small parts that same white as well.

Is that your car in your avatar photo? That's very close to what I was thinking mine will eventually look like.

[Lidodrip]

Yes - that is my finished car. It is Viking Blue with Wimbledon White stripes. I really like Brittany Blue too, I think that color has a little more silver in it. I used Prismatic Powders for powder coating. They have so many colors and will send you free samples - I am sure you could find a white that matches what ever you decide on. Powder coating does tend to be more durable than painting. Here is another picture of my car:



James

[wantscobra]

It looks fantastic. I'm jealous. I wanted to be a lot closer than I am to that state by now.

[Misterfubar]

I have the same 13" GT brakes and IRS, but I am using the FFR 17 x 9/10.5 wheels (not sure how they compare to the FR500 wheels). The wheels did rub on the calipers and I had grind down a small portion of the ridge on the caliper. It wasn't a big deal, but I kicked myself for not checking fitment before I powder coated the brakes. Had to re-powder coat, but all is well now.

Caliper modification:



Finished product:



James

I had this same issue, but got lazy and used a 5mm hub-centric wheel spacer. No issues 5k miles later with the spacers.

You'll also need to pay close attention to where any wheel weights are placed when balancing.

[CraigS]

Unfortunately you have to try and see. I did my 15 IRS retrofit and found one set of my Bullit wheels would not fit. The other 2 sets cleared. I would order one of the 10.5 wheels for a test fit. Worst comes to worst you are only out the cost of one wheel. You could also hold off on swapping in the new wheel studs. Could be that a thin shim like Misterfubar used would fix any interference but that 'might' need a longer wheel stud.