Wheel backspacing and tire size
 

As much as I like the sidewall appearance of the Polysteel tires I have, they're too skinny. So I'm going to put 255/60 15's on the back and 245/60 15's on the front. I could put them on the 15x7 wheels I have but the rear's would balloon out a bit so I think I'm going to go with 15x8's all around.

The question is, what backspacing should I use 4" vs 4.5"? I believe my 15x7's are 4". Right now the outside edges 225/70's are sitting pretty deep into the wells, especially on the rear. If I'm understanding this correctly, if I go with the 4.5" then that's going to split any additional wheel and tire width between the inside and outside, leaving the wheel/tire more or less centered where it is now. So basically I get a little more width on each side. If I stay with a 4" backspacing then it's going to put all the additional width on the outside, correct?

I don't think there would be any clearance issues either way. Which do you think would look better? Or should I use 4.5" for the front and 4" for the back to give it more of a staggered look, a little more narrow track in the front and wider in the back?

jhein, I have both BFG TA's and MT Sportsman S/T's in 255/60R15 size on 15x7 Honeycomb and plain steel wheels and they don't appear to balloon much, if any at all. Either set doesn't rub anywhere front or rear. It's interesting that the MT's are a little taller and narrower than the BFG's of the same size.

I think a 4 1/2" back spacing would be about right for the F-body for a 15x8 wheel.

Dennis

245 60 15 Front & Rear for reference.

Thanks gents for the helpful info. Based on the way those 255's look on those 7" wheels, I think I'm gonna just go with my current 15x7 wheels and put 245's on the front and 255's on the rear.

Not only will that save me from buying new wheels, but right now the 15x8 wheels with the more correct finish aren't available. You can find them in a chrome finish on the "spokes" and rim, but not the flat/matte finish. I don't really mind the chrome look myself but I'd like to keep it as close to stock in appearance as I can.

I think that is a wise decision! The TA looks great btw!

Dennis

This is 255 on the rear and 245 on the front. Never rubbed

Craig, Where is that at? I see Mike's Formula behind your TA (he runs 245's I believe?). The 245/255 look is a natural for the 2nd Gen Birds.

Dennis

Are those on 7" wheels too?

Nice car, BTW and to everyone one the thread, all nice cars.

Wheels
 

A little off topic but if you were to order wheels,where would you buy?
Specialty wheels or wheel vintiques.? Which ones have a better color an finish.thanks

Dennis, that is Uncle Judges Estate. 245 is the go to on these cars. Here are pics of mine with the Repop F60 and BF Goodrich 245s all around. Not sure why it’s upside down lol

Mine are 15 / 7 stock rally II

I was looking at Wheel Vintiques. The reviews have some complaints about the durability of the finish but they also have a lot of good reviews too. I think these are the wheels on my car now but I haven't looked that closely. I do have some small chipping/peeling of the powder coat around the lug nuts.

Just now heard of Specialty Wheels for the first time. Looks like Coker Tire sells them. Wheel Vintique seems to offer more size and backspacing options but Specialty Wheels has a better warranty and maybe better finish, don't know.

Correct.

Timely thread as I'm also in the market for both wheels and rims...thx

Because my car sits higher than it should in the back I prefer to push the wheel out so the outer edge of the tire is just inside the top edge of the opening to try and "hide" all that space...so the 4" backspace to push the tire towards the outside is what I'd prefer...my question then is, what's the widest tire I could put in back so that the outer edge of the tire just stays inside the top edge of the fender opening and should a smaller backspace be considered?

IAs far as the rally2 wheels go,,,,I ordered some custom 4.75" BS 15x8 rally 2's for my 70 back in august from wheel vintiques.,,,yep august. I call every month and they say theyre still waiting for the outer rings from their supplier which is a company here in the states. Couple of weeks ago they told me hopefully Ill have them in June. They powder coat the rim in argent silver which is a good match and durable. Then they paint the center in the charcoal grey which is not a good match and it scrapes off very easily. I scraped off the charcoal grey,sanded and repainted the centers in eastwoods charcoal grey and clear coated with their satin clear in a can. Much more durable now,,,,I actually got the center caps on without flaking it off. I have the vintiques 15x7 on the front with 4" BS. Just waiting on the 15x8's for the back. 245/60-15 in the front and 255/60-15 in the back but this is on a gto not a firebird. Like was said,,,you cant even find their off the shelf rally 2 sizes right now.

The only way I can think of is to actually take measurements. You would need to know what your current wheel backspacing and rim width is. Then you'd have to take measurements of where your current tire is sitting in the well. Then you'd have to look at all the combinations of rim width, backspacing and tire width to see where they would all sit compared to what you have now.

My rears are sitting pretty deep in the wells, I haven't actually measured but it's at least 2-2.5". If I stayed with 4" BS then I could easily do a 275/60. That has a section width of 11", 2" wider than my 225/70. Also that tire is 28" tall so it would help fill up space if the car sits high. You may even get away with a 295/50 as far as width, but that is a 26.7" tall tire so it won't fill the well as much. Don't know for sure about clearance for a tire that wide but I think if you stay with a stock 4" BS then it shouldn't rub on anything on the inside. All of that assumes you're staying with a 15" wheel of course.

thx, i'm fairly sure my 15x7s are stock rims, i'm not sure what the stock backspacing is, 4? 4.5? have no idea......

I think the stock BS is 4", but hopefully someone else will confirm that.

It's fairly easy to measure if you take the wheel off.

I checked the backspace on a few factory Pontiac 15x7” Rally II wheels and they measured close to 4-3/8”.

I would assume just about any 15x7” factory wheel should be the same or very close.

thats what the 14x7 Rally2 has for a BS also.