14 to 15 inch tires and wheels

[Kevin J]

I have a '73 convert that needs tires so I'm considering upgrading from the 215/70/14 white walls to an aftermarket aluminum wheel and 15" tires. Tire rack recommends a 7" wheel with 215/65/15 tires but I'm reading that a lot of members are using tires larger than that.

Id like to go as large as reasonably possible.

The car has good springs and no sag but I'm still concerned about the tires hitting the wheel wells.

Any advice on sizes, wheel offset, etc. would be greatly appreciated.

 

[Mister 4x4]

Just for an idea, I'm running 245/60R15s on 15x8s up front, and 295/50R15s on 15x10s (with 5.25" custom backspacing) out back.

No rubs, no steering issues, no nothing.

I think there are a few who are running even wider wheels/tires without issues, but not many and not that much wider.

Edit: Oh yeah, here's a couple pics (before I swapped on the new rear wheels with the custom backspacing, that is).

Austin Vert (Greg) has a sweet '73 'vert with a similar wheel set-up, and it's oh-so-nice. He went with Magnum 500s, as well.

Hope this helps.

 

[Boss1Ray]

Be careful. Various backspacing on wheels can cause you problems.

Personally - I like to find someone who has a setup I like and copy theirs (complete tire size, Wheel size & backspacing for front and back - if different. I did that with Chuck (c9zx) and his setup on his KILLER 72 Mach 1. (THX Chuck!) BTW this is one of my favorite Mustangs!!!!!





Here is his (and soon to also be mine) setup:

... 245x60x15, on a 15x7 rim with 4.25 inch back spacing, is the largest 15 inch tire that will clear in the front. A 275x60x15 will clear in the rear using a 15x8 rim with a 4.5-4.75 back spacing. All 4 rims and tires being the same size will permit tire rotation. Chuck

235/60/15's or 245/60/15's work well if you want all 4 to be the same size.

Ray

 

[Mister 4x4]

Having 'staggered' sizes front to rear definitely eliminates some options when it comes to tire rotation.

As Ray mentioned, be careful with the backspacing and sizes - they can lead to issues that become expensive over the long run. Initially, I bought some 15x10s that came off-the-shelf with 4 1/4" back spacing, which put the tires sticking out of the rear wheel wells about an inch or some (which you can kind of see in the pictures above). After 'buzzing' the tires on the lips as the suspension compressed going over a bump, I had to get in touch with Cragar for some custom backspaced wheels (5 1/4"). That was $400 I could've saved had I known there was an option to custom order the rims.

The alternative is damage to the car and/or wheels & tires. Lose/lose either way if you're not careful about it.

 

[turtle5353]

If I had to do it over again I wouldn't of went with 15" rims. Its getting harder and harder and more expensive to get decent 15" tires anymore. I would go with 16 or 17". But that just my opinion on it. A 15" and 16 " rim side by side isnt much difference. Well actually about 1 " lollerz

 

[Mister 4x4]

On a 'vert, I wouldn't have any issues going with a 17" or even 18" rim - the bigger wheels and lower profile tires work with the body lines better, IMHO. With the sports roofs, not so much - I just think they look better with a little bit more sidewall on the sports roofs (again, just my weird hang-up). I am actually starting to warm up to the idea of 17" wheels on mine (when 15s become too expensive and/or hard to get), but they'll have to be just the right design for me to actually go that route. Torque Thrusts and full chrome KMC Novas are about the only ones I'd consider at this point - 17" Cragar S/Ss just look weird to me for some reason.

Yeah... apparently, I'm a picky SOB. rofl :whistling:

 

[mach71351c]

You can easily go with 235/60/15s on 7" wheels. Probably the most commonly seen on our cars. You can run a 245/60/15 which I thank looks a little better. They will rub on the steering box bolt on a hard left turn. Not enough to hear or feel it in the wheel. Just enough to polish the head of the bolt.

I'm running 245/60s on 7s up front and 255/60s 8s out back.

 

[Totalled]

245/60/15 on a 15x7 front, 275/60/15 on a 15x8 rear.

 

[Kevin J]

::thumb:: This is fantastic information! Thanks everyone!

 

[luxstang]

255/60/15 on original 15x7 Magnums on all 4. Suspension lowered a lot! (One inch shorter coils that on top had one compete turn cut off)

No rubbing except for the rubbing on the steering box bolt that Mike mentioned. That only happens when you maneuver or pull out of a parking lot and turn the wheel ALL the way to the left. Never during normal driving.

But mine did that also with smaller tires.

 

[mweeps]

245/60/15 on all four corners on 15x7 Magnums for mine.

 

[Stanglover]

I have a '73 convert that needs tires so I'm considering upgrading from the 215/70/14 white walls to an aftermarket aluminum wheel and 15" tires. Tire rack recommends a 7" wheel with 215/65/15 tires but I'm reading that a lot of members are using tires larger than that.

Id like to go as large as reasonably possible.

The car has good springs and no sag but I'm still concerned about the tires hitting the wheel wells.

Any advice on sizes, wheel offset, etc. would be greatly appreciated.

If you go to 15's will you not have to change your speedo drive gear? I guess not if the diameter of the new 15" tire is the same or very close to it as the 14's. Just sayin'

 

[Mister 4x4]

Speedometer drive gear requirements are based on a combination of the rear axle gears and overall wheel diameter. These two factors are critical making the determination of which gears you want to run, based on where you want the engine's power band to be engaged.

Changing rims/tires only affects the speedometer gear and rear axle ratio if you change the overall diameter of the wheel. Going with larger diameter rims and smaller tire sidewall aspect ratio is how you keep the overall wheel diameter the same.

The formula for reading tires is pretty simple:

P 205 / 60 R 15

P - stands for Passenger Tire (other letters can be here, like "LT" for Light Truck, etc.)

205 is the tire center section width in millimeters. 205mm is how wide the tire is

60 is the sidewall aspect ratio, based on a percentage of the tire's center section width. In this case, the sidewall is 60% of 205mm

R15 is the rim size, in this case 15 inches.

Use that information to determine the overall diameter of your wheel using an online tire size calculator such as: https://tiresize.com/calculator/

From there, you can pick out the right size tires to fit the bigger rims so you can maintain your overall wheel diameter avoid having to change the speedometer gear.

For example: my '71 came with 14" rims, and was wearing 195/75R14 tires. I upgraded the rims to 15" rims with 245/60R15 tires up front, and 295/50R15s out back, with very little change in the overall wheel diameter size... therefore, no real need to change the speedometer gear, since everything is still rolling and spinning at about the same rate as before.

 

[Musti]

@mweeps

Hi,

which back spacing have the blue stang at the pic at the front and rear axle.

Thanks

Juergen

245/60/15 on all four corners on 15x7 Magnums for mine.

 

[jbojo]

225/60/15 on 15x7 on front and 245/60/15 on 15 x 8 on rear.