[Roger Bettoni (Roger)]

Age old question I know, but here goes anyway.
I'm considering buying a set of rims - 2 x 15"x7" and 2 x 15"x8" that are available second-hand (multi-style to suit 4.5) for my '71 chally. I've read a few of the previous threads on tyre sizes but am looking for some advice. BF Goodrich radial Tee/Ay's are my tyre choice and from what I have read the P235/60 R15's for the front and P275/60 R15's for the rear seem to be a popular set-up. Any conflict with springs, guards on the front or rear with this combo?
Thanks for your considered opinions...
By the way Dave, when I tried to post the tee/aa's in capitals as you would normally read them, an error message came up advising me that this discussion board didn't permit this??

[Roger Bettoni (Roger)]

Okay Dave - I know what you're thinking, so don't say a thing...

I did find several posts on the topic and eventually found your answer to my above query, given some two years ago as below...

Thanks mate for having the info on the site for me to find. Unless you have any new ideas to add, I assume that there's no conflict with springs or rubbing of the fenders with my choice of tyre sizes.

Cheers...R

Here are what I think (with my limited understanding of tyre technology) are the MAX tyre sizes that fit these wheel widths.

On a 5.5 inch wheel I would fit a 195 to a 205 tyre.

On a 6 inch wide wheel I would fit a 215 or 225 tyre.

A 7 inch wheel I would use a 235, 245 max.

An 8 inch a 265 - 275 max.

The IDEAL situation is to have a tyre tread width that is just 2 inches over the wheel width. The wall of the tyre can only work as designed if fitted to the correct width wheel. The wider the tyre you fit to a wheel the more the tyre wall moves from the vertical to the horizontal.

[Dave-R (Roppa440)]

The only thing you have to watch out for is the backspacing (sometimes called offset) of the wheels. Too little and the tyre will be rubbing the wheel arch. Too much and the tyre will rub the spring.

[Roel Bester (Roelb)]

Roger, I just fitted last week the following to my '71 Challenger, with no problems:
15 x 7 with 235/60 fronts
15 x 8 with 255/60 rears
Tyres are Uniroyal Rally GTS

[Roger Bettoni (Roger)]

Not having even seen these wheels I'm considering buying, I don't know what back spacing they have. I'll contact the seller and ask if he knows.
Roel - how much clearance to the spring and/or fender do you still have with the 255's? Do you think you could have gone (20mm) wider still?
I'm looking for the best appearance and stance I can get at the rear. I read somewhere on these pages that someone else put a set of 275's on the rear and had no problems.

[Tim Ellison (Tim)]

Roger,

I'm going through the trauma of fitting 10x15 wheels on my '70 at the moment. From what I've learned along the way (mostly from Dave) if you go with 8" wheels with a backspacing somewhere between 4.5" and 4.75" you should be clear of the leafsprings and the wheel arch lips.

Does this sound ballpark to you Dave?

[Roger Bettoni (Roger)]

Thanks for the advice Tim. I've contacted the seller of the wheels and he says the backspacing of the fronts is 4" and the rears is 3 3/5ths" although he says he's relying on his memory and will re-measure to confirm. Ultimately, I'll make the decision about tyre sizes based on what I find myself and can organise through a "mate" who can get me tyres at cost price + 20% which is a big savings.
While the wheels are not new and require a bit of spit and polish, they look great and the "price is right" so was too good an opportunity for me to pass-up. As they're 15" they'll suit my plans for the disc brake front end improvements too.

[Phil Raynor (Philth)]

Love them wheels! Keystone Classics, aren't they? You were right to snap 'em up, Roger!

[Tim Ellison (Tim)]

They look to be in excellent condition from the photo Roger, nice style too.

I think the fronts should be ok. My backspacing is 3.75", and they fit fine. Not sure about the rears though, the lack of backspacing may push them out towards the wheel arch lip. I've heard from other MB members that you can gain a few crucial mm by removing the wheel arch trim.

Dave's the guru though, he answers about 20 wheelfit related questions a week (18 from me).

[Roel Bester (Roelb)]

Roger, looks like youre all sorted out, but anyway, I have measured my clearances as follows:
45mm between wheel and spring, about 15mm outward to the fender, mind you the innerlip has been rolled by previous owner. Beautiful wheels you have there

[Dave-R (Roppa440)]

ooh! I used to have a set of them on my Aussie Charger. I still had the rear 15x8 pair until recently when I gave them to Dave McBride. They were rusty and pitted though. These wheels do not like living outdoors on the car in all weathers.

Sorry i have not been around today. Been watching someones bladder being cut out via a very small hole or two in their belly. It was a 9 hour operation because they make a new bladder out of a length of bowel. I just get to transmit TV and audio to groups of interested people. Boring for me but it's a living.

The best thing to do when thinking about new wheels is to MEASURE!

Take off the rear wheels (both sides) and sit the axle on stands so the car is about level. Then get your tape measure out. If you know the backspacing of the wheel you can deduct that from the wheel width and that gives you the measurement from the face of the rear drum out-over. Take into account the width of the tyre too of course. Work out how much wider the tyre is and add half that to your measurement.

Putting a straight edge vertically up against the wheel lip gives you something to measure too.

You can put an edge across the brake drum and measure back to the spring too. Be sure to measure to the rear half of the spring because that is the tightest part (about 10-12 inches from the centerline of the axle).
It is not a perfect way of doing it but as long as you are not pushing the limits of what will fit then it should do.

[Roger Bettoni (Roger)]

Yup, Keystones they are, and like 'em I do - very much. Apart from minor surface rust, they look to be in great condition (came off a '68 Charger so I'm told).
Not in a hurry to buy the tyres just yet, as I must first repay my mates at Visa, so plenty of time to ponder and research the issue.
Roel, I think that given your measurements, I can go the extra 20mm to 275's but will check the backspacing carefully first. I'll let you know how I go when I see my tyre mate. I may well end up doing the DR surgery on the wheel arch lip to accommodate the extra 20mm's and get that extra wide stance. After all, these are American cars and as they say "bigger is better".

[Roger Bettoni (Roger)]

Figured that they would rust easily too Dave, given they're chrome on steel. Mine is thankfully parked indoors all the time, so should not be too much of an issue. Thanks for the guidance in measuring technique. Am I to understand that the leaf springs taper outboard at the back, thus your suggestion to measure 12" from the axle?

[Dave-R (Roppa440)]

That's right.