Considering swap from 17" to 15" wheels

[CCRsAC]

I'm looking for thoughts on a mid-stream change in my build. When I started this project, I was going for a more track-friendly build with just a few period correct touches. Now, I'm leaning way more towards vintage and not intending any track-use at all. I have the SVT brakes, though, so I went with 17" FFR Halibrand-replicas (9" front / 10.5" rear). Given the path my build has taken, I'm considering modifying or replacing the front caliper brackets and going with smaller diameter rotors, then switching to the 15" FFR wheels with Goodyear billboards. I've done some research, and the caliper mount and rotor change are doable mods that allow the use of 15" wheels, but I'm not sure whether I'll have issues with getting the backspacing correct on the 15's, unless I go with custom made wheels.

Thoughts?

[Gordon Levy]

I have some 4 piston systems that would clear 15" wheels just fine. You would need to drop your rotor size to 11" and modify the brackets extensively to work. It's still going to be tight.

[daltmcintyre]

My plan is to use SN-95 ('94-'95) with PBR calipers with a PIN drive width setup. It's my understanding that this setup will work with 15" Trigos.


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[NAVYDUDE]

I have new unused rotors and calipers from my complete kit if interested...


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[timp2]

I have the setup that daltmacintyre referred to and it works just fine. I have pin drive IRS and I can tell you that extended drives (road trips) are comfortable. I think the 15 inch wheel and tire combination also softens the ride somewhat. It is comfortable and predictable.

[steno]

Chris,
It's your car, so do your own thing. I will tell you this...I've seen your build first hand...it's stunning! I'm sure it will be a good call.
Sten

[CCRsAC]

Thanks for the tips, guys!

And Sten, thanks for the compliment - it was fun having so many members from the Windy City Cobra Club stop by a couple weekends ago. Drop by anytime!

[CraigS]

I think you should go w/ your original wheel/tire plan. Heck, if you want to, look into some slightly taller 17 tires. I am just guessing here but usual rears are 315/35x17s. Are there any 315/40 or 45 or 50 x 17s available? That's just me thinking...

[CCRsAC]

Originally Posted by CraigS

I think you should go w/ your original wheel/tire plan. Heck, if you want to, look into some slightly taller 17 tires. I am just guessing here but usual rears are 315/35x17s. Are there any 315/40 or 45 or 50 x 17s available? That's just me thinking...

You know, that's a very interesting idea. That would accomplish a few things; 1) the tires would have a bit less of the "black rubberband" look from the sides, 2) the ride would be cushioned just a bit more, 3) the tire to body clearance would look better - i.e., the tires would fill-in the wheel wells a bit better, and 4) the increased sidewall would allow a bit higher ride height, while still looking good at the tops - i.e., tucked up into the flares.

I'm going to look into this - thanks for thinking outside the box on this one!

[DMW]

I agree with you. I have 17" Bullitt wheels which I love but the tires are too skinny on the sidewall (Sumitomos: 17x315x35 rear and 17x245x45 front).

I really like the look of the taller sidewall of 15" wheels and they seem to fill the wheelwell better. I am in the market for tires over the winter and will be looking for some taller ones.

[DMW]

I did some quick research on Tire Rack.com

I currently have 315/35/17 in the rear. This translates to a side wall of 4.34 inches and an overall diameter of (4.34+4.34+17.00) = 25.69 inches

I think a typical size for a 15" wheel is about 195/65/15 for a sidewall of 4.99 inches and an over diameter of (4.99+4.99+15.00) = 24.98 inches.

If my math is right, they are just about the same size overall but I think the curved sidewall on the 15" rim makes it look much fatter.

I found some tires that are 225/65/17 for a sidewall of 5.76 inches and an overall diameter of (5.76+5.76+17.00) =28.52 inches - pretty big.

Another is what is found on a typical late model Mustang GT: 235/55/17 for a sidewall of 5.09" and an overall diameter of 27.18 inches.

So far this is the best I found in 17" tires. Send me a PM if you find a good 17" solution.

[CraigS]

I did some searching at tire rack today and my idea didn't pan out too well. So maybe try 16 inch.If you go to tire rack and 'search by size' you will come up w/ a list of tires that size.If you click on one of them, you will then have some tabs available one of which is 'specs'. That gives the dimensions of that size tire and of all the other sizes that tire has available. Pay attention to the 'overall diameter' column.
If you don't find anything to suit you I would suggest doing a search on this forum for 'goodyear billboards' or similiar. I think you will find that they are not a very nice tire to drive on. I remember one thread where someone made some faux billboards w/ stencils and paint. If you decide to go 15 inch here are two possibilities.
CooperTiresConsumer - Cobra Radial G/T<span class='trademark'>™</span>
235 on the front and 295 on the rear which may be a little wide but doable as a friend w/ a MkI found out recently. They zing just a little over big bumps which could be fixed by a ride height increase.
Mickey Thompson Performance Tires & Wheels
26x10s on the front and 26x12s on the rear. I have no personal experience w/ these but they got a lot of good reviews a few years ago here so do another search. Good luck.

[306rangerfordguy]

You might want to check what size tires are available for the 15" rims first. I was considering the 15s when I bought mine so I could get the white lettered tires but the tire size selection for 15" rims seems to be slim. I think the 15s would give a smoother ride. My car has the same 17" rims you have and it is slightly rough riding because of the short sidewall. I have 245s on the front and 315s on the rear.