Road Runner Nest

Hey I know there is already a topic sort of like this but mine is a bit different. Ok the question is, what is the biggest tire size that can fit on the back of a '72 road runner if it is mounted on a Rallye size 15-8 with NO backspace?
Could a 275/60-15 work, or maybe a 295/60-15?

I'm not sure where you are going with "NO backspace". That would have the wheel itself partially outside the quarter panel. I'm not sure you could get a set of rallye wheels made up with no backspace at all and have them look ok from the front.

Unless you mean a 15x8 rallye with just the factory backspace, which I think is 4.5". (Ok all you rallye wheel guys, correct me if I'm wrong there. ) Anyway, if you mean just using a stock rim, you could easily to 275's, 295's would be pretty close clearance to the quarter panel. On the rims I have for Project Blue Bird, they have 4.75" backspace, and I have the 295's exactly centered in the wheel house, with 3/4" clearance from both the spring on the inside and the quarter panel on the outside. Figure the factory rallye would move that whole thing 1/4" outward, so you'd be looking at 1/2" or less from the quarter.

If you looked at 275's you'd have a good bit more clearance due to the smaller tire in general, but also, you'll drop a good bit in section width on the tire since you wouldn't have the same sidewall bulge that you do fitting a 295 on an 8" rim.

Hope that helps!

Dave, good response, do you have a picture of the 295 under your car?

Yea I don't know what I was thinking with the whole"no backspace" thing, but thanks for the info, although I am a retard.

72, don't feel bad, we all have those days. Only way to learn is to ask questions. As I've always said, there's no such thing as a dumb question - just dumb people... er... no wait... that's dumb ANSWERS.. yea, thats it.

Anyway, glad I was able to help you. If you want, I can see if I can dig up the spreadsheet I used in working out tire widths, wheel size and backspace. I'm not sure if I saved it, but knowing me, it's around here somewhere.

71GTX, well, here's what I have:

A couple from when I did a test fit on my SSP:









This is the only one I have of them on the Road Runner. It doesn't have the best detail, but it's better than nothing.

Dave - thanks for the picture, that tire looks small (dia) in the first pic but looks great in the rest. I know you say it is a 295 but what is the complete number on it.
The rims are 4 3/4" backspace, correct?
You have made my day!!!!

I too would also like to see the spreadsheet.

Nick

Those are 295-50-15s.

I'll dig for that spreadsheet tonight, and see what I can find on it. I'll post here if I do find it!

Dave wrote:Those are 295-50-15s.

I'll dig for that spreadsheet tonight, and see what I can find on it. I'll post here if I do find it!

any luck finding it?

To convert Metric to inches just multiply by .03937

for tread width....
EX. 275/60/15 275mm = 275 X.03937 = 10.82 inches tread

Tire diameter
10.82" X .6 ,(60%)= 6.5" sidewall height

6.5 X 2, ( to sidewalls) = 13" + 15" diameter wheel = 28" tire diameter


That will get you your tire dimension- the backspacing you'll have to figure with a straight edge from the wheel mounting face and a ruler to the wheel housing lip and spring. You should be able to determing the back spacing from there.