[hdpontiac]

i have a 69 gto and are looking to put 15inch aftermarket rims and tires without rubbing issues especially the front I would like to use 275-60-15 for the rear but I need to now what rim is recommended for front and rear with correct offset and tire size any help is appreciated

[JLMounce]

This isn't really the answer you're looking for, but you're going to have to measure it. Especially when you are pushing fitment sizes, nobody here can account for any abnormalities for your specific vehicle.

If you came here saying you wanted a 245 series tire in a 15" fitment, I could tell you that you'd be fine picking up a 8" wheel on a 4.5" backspacing without a problem.

Going with a 275/60/15 in the back is a large tire that will require you to measure and nail the wheel fitment for your car. Otherwise I can pretty much guarantee you'll have rubbing issues you'll have to deal with after the fact.

Off the top of my head if you ran a 9" wheel with 5 to 5.25" backspace in the rear, you'll probably be close. Run a 235-245 section width tire on a 8" wheel up front and assuming you haven't done anything to the track width you should be fine at 4.5" backspacing there.

[redhawk44]

While I am not yet ready to tackle this problem I know this will be an issue when I do get to that point. I don't know if this item would be of use ( http://www.summitracing.com/parts/php-01201 ) but I saw it in Summits catalogue. The catalogue actually shows it assembled and it is easier to envision it in use. Please keep us updated on your progress.
Jeff

[HWYSTR455]

Is there a reason you are limiting yourself to 15" wheels and tires? 17s and 18s provide a much broader tire selection.

Depending on your brakes, or should I say potential 'future' brakes, the wheel 'spokes' can also be a concern. Depending on the caliper, it's possible to have clearance issues.

The upper control arm you run up front can also be a concern, once you go beyond 4.5" backspacing. Not to mention your brake setup, which can lead to the tire contacting the sway bar on full lock.

If you get your ducks in a row, it is possible to run a 295-305 in the rear, and if you're lucky, 315, with no body mods.

Up front, you should be able to run a 255 with no problem, and up to a 275 if you plan properly.

Another thing to note is some wheel manufacturers measure from the inside of the bead lip of the wheel, and some measure from the outside. If a wheel size is listed as a '15x8.5' for example, they measure from the outside, '15x8' is measure from the inside, both are the same width.

Backspacing is the best measurement to use when going for fitment, since 'offset' can be calculated slightly different due to how the manufacturer measures.

I ran a 17x11 on the back of my stock LeMans, with 6" backspacing, and was able to squeeze a 305 on there. I dropped back to a 295 at one point due to the fact I couldn't find a matching front size I wanted.

I ran 17x9 on the front of the same car, with a 5" backspacing, and 275s, but I had tubular uppers, not sure if it would have cleared with OE arms.

I had an Eastwood wheel fitment tool and it was more difficult to use and read than it was worth. Best way would be to have a friend with wheels and tires that are close to the size you want to run and swap them, then take measurements.

Keep in mind that tires vary in width too, not just tread width, but overall width too. If you look on TireRack.com, under 'specs' for a particular tire, you will see total width and tread width dimensions.

.

[John62]

Have a talk with ABC Performance in Michigan. They carry things like sway bars designed for large tires and so on.

[David Jones]

I ran 245/60's on the front of my 69 a few years ago. Hated it. I went back to 215/70-15's a while back and the car is much nicer to drive.

[HWYSTR455]

Originally Posted by David Jones

I ran 245/60's on the front of my 69 a few years ago. Hated it. I went back to 215/70-15's a while back and the car is much nicer to drive.

Ok, I'm curious, what did you hate about running a wider tire? It's only 3/4" wider than a 215?

.

[David Jones]

Originally Posted by HWYSTR455

Ok, I'm curious, what did you hate about running a wider tire? It's only 3/4" wider than a 215?

.

A quick look at the spec's for a 215/70 Radial T/A show it at 6.5"wide. A 245/60 is 8.5". Unless I'm figuring incorrectly that's a 2" difference in tread width, not 3/4". 2"s makes the 245 loosely 30% wider at the tread than the 215. 30% finds that much more to track along with or bounce off of. The ride with the 215's is markedly better. I did like the look of the 245's better but I drive my car a good bit and the trade off simply isn't worth it for me.

[HWYSTR455]

My bad, was comparing 60 series, overlooked you went to a 70 series.

Tracking/tramming can be controlled by alignment I believe. Some also has to do with tire design/construction.

.

[David Jones]

Originally Posted by HWYSTR455

Tracking/tramming can be controlled by alignment I believe. Some also has to do with tire design/construction.

.

The alignment was in spec.
I suspect the 6 pound weight difference 25/31 has an impact also.
Tire design/construction? May be, but when buying white letter tires these days and liking the overall look of the Radial T/A, well, they are what they are.

[78w72]

always thought tire size numbers worked like this. the first number is the width of the tread in millimeters, so a 245 is 245mm wide. then the next number is the ratio of the sidewall based on that millimeter number, so a 60 series is 60% of 245 sidewall.

if thats correct, a 245/60 is only 30mm wider, which is 1.182inches wider than a 215/70... not 2" & not 3/4". but the 215/70 has a taller sidewall based on 70% of 215 vs 60% of 245. right? or wrong?

either way, a 215/70 may "drive" better for road feel etc, but a wider 245/60 will "handle/perform" better being its wider & less sidewall.

[David Jones]

Originally Posted by 78w72

always thought tire size numbers worked like this. the first number is the width of the tread in millimeters, so a 245 is 245mm wide. then the next number is the ratio of the sidewall based on that millimeter number, so a 60 series is 60% of 245 sidewall.

if thats correct, a 245/60 is only 30mm wider, which is 1.182inches wider than a 215/70... not 2" & not 3/4". but the 215/70 has a taller sidewall based on 70% of 215 vs 60% of 245. right? or wrong?

either way, a 215/70 may "drive" better for road feel etc, but a wider 245/60 will "handle/perform" better being its wider & less sidewall.

I cheated. I looked up what BF Goodrich said the widths are.
I do believe your calculations are correct in theory though.

[78w72]

another thing to mention, check other companies specs too... not all brands measure the same or calculate differently for some reason. a bfg 245/60/15 isnt always the same size as another245/60 brand.

[Blued and Painted]

Originally Posted by David Jones

The alignment was in spec.

The old school alignment spec's with positive camber and negative caster may not be compatible with the wider low profile tire. Wider tires on modern cars is common, along with Zero or negative camber and +2 degrees or more caster.

But yes, in general, lower profile tires will give a more sensitive ride.

[SS-TA]

The 245 mm is the cross sectional width NOT the Tread width. Your calculation of sidewall height is correct.

[android 211]

A few people have posted on here that a 245/60-15 in front rubbed inside the wheelwell on their 69's. 235 was as wide as most people could go with a 15" wheel. A 245 fits fine on a '70 because the wheel opening shape is different.