Looking for new wheels; need help with sizing

[Pious_Paladin]

Hello everyone! So I have a 72 Dart with 73 4.5bp discs up front and an 8 1/4 rear out of a B body in the back (at least that is what I believe I have). Currently I am sitting on 15" Cragar SS wheels front and back and they are starting to get rusty, so time to replace since repair is more than replacement. Right now I am running 215/65/15 in the front and 235/60/15 in the back without issues. I say that because I have no idea what the backspacing on the wheels are, so I am hoping that will help determine it. Attached a couple of pics to show the current setup. I have been admiring these https://www.jegs.com/i/JEGS/555/670106/10002/-1 but not sure if the backspacing will work.

 

[srduster340]

My brother has a '71 Dart with 15 X 7 police wheels front & rear. I just measured the backspacing & it's 4.5". He ran 255R6015's with no issues. We tried 27560R15's but they rubbed the during turns. Hope this helps.

 

[Pious_Paladin]

Update: I did some more digging and since my wheels are the 5x4.5/4.75/5.0 I have determined that they are 15x7 +3mm 4.13" backspace on the front and 15x8 -6mm 4.15" backspace on the rear.

 

[72bluNblu]

Hello everyone! So I have a 72 Dart with 73 4.5bp discs up front and an 8 1/4 rear out of a B body in the back (at least that is what I believe I have). Currently I am sitting on 15" Cragar SS wheels front and back and they are starting to get rusty, so time to replace since repair is more than replacement. Right now I am running 215/65/15 in the front and 235/60/15 in the back without issues. I say that because I have no idea what the backspacing on the wheels are, so I am hoping that will help determine it. Attached a couple of pics to show the current setup. I have been admiring these https://www.jegs.com/i/JEGS/555/670106/10002/-1 but not sure if the backspacing will work.

View attachment 1716378878View attachment 1716378879

The 3.75" backspace won't work for you on a 15x7". In the front you'd want more like 4.25" of backspace. If your current rear wheel are 15x8 with a 4.15" backspace and they are well centered you definitely don't have a B-body 8.25" in there unless it was cut down, you'd need more backspace than that. If your current set up is well centered between the quarter and the springs your rear axle has to be fairly close to A-body width, although that's a range itself between the A-body 8 3/4 and narrower A body 8.25.

These would work, 15x7 with a 4.25" backspace

Vision Wheel 141H5765GB6 Vision American Muscle 141 Legend 5 Series Black Wheels | Summit Racing

And these are the 15x8's, they have a 4.5" backspace so you'd want to make sure you have about 3/8" to give up to the springs with your current wheels.

Vision Wheel 141H5865GB0 Vision American Muscle 141 Legend 5 Series Black Wheels | Summit Racing

Since you have 235's in the back you could easily run those with 15x7's and just use the same wheels front and rear. Even a 255/60/15 will fit on a 15x7" wheel pretty nicely, although on a Dart even with good backspacing a 255 is pretty tight (But definitely has been done!). A 245/60/15 is usually a safer bet on most Dart's just because of the wide range of body tolerances on these cars.

My brother has a '71 Dart with 15 X 7 police wheels front & rear. I just measured the backspacing & it's 4.5". He ran 255R6015's with no issues. We tried 27560R15's but they rubbed the during turns. Hope this helps.

Factory 15x7" police wheels have a 4.25" backspace, just FYI.

 

[Pious_Paladin]

The 3.75" backspace won't work for you on a 15x7". In the front you'd want more like 4.25" of backspace. If your current rear wheel are 15x8 with a 4.15" backspace and they are well centered you definitely don't have a B-body 8.25" in there unless it was cut down, you'd need more backspace than that. If your current set up is well centered between the quarter and the springs your rear axle has to be fairly close to A-body width, although that's a range itself between the A-body 8 3/4 and narrower A body 8.25.

These would work, 15x7 with a 4.25" backspace

Vision Wheel 141H5765GB6 Vision American Muscle 141 Legend 5 Series Black Wheels | Summit Racing

And these are the 15x8's, they have a 4.5" backspace so you'd want to make sure you have about 3/8" to give up to the springs with your current wheels.

Vision Wheel 141H5865GB0 Vision American Muscle 141 Legend 5 Series Black Wheels | Summit Racing

Since you have 235's in the back you could easily run those with 15x7's and just use the same wheels front and rear. Even a 255/60/15 will fit on a 15x7" wheel pretty nicely, although on a Dart even with good backspacing a 255 is pretty tight (But definitely has been done!). A 245/60/15 is usually a safer bet on most Dart's just because of the wide range of body tolerances on these cars.




Factory 15x7" police wheels have a 4.25" backspace, just FYI.

Thank you!

Do you think I could get away with 235/60 on the front as well with a 7" wheel? I'd like to be consistent if the wheels are the same all the way around.

 

[72bluNblu]

Thank you!

Do you think I could get away with 235/60 on the front as well with a 7" wheel? I'd like to be consistent if the wheels are the same all the way around.

Not likely. The problem gets to be the height, a 235/60/15 is over 26” tall and is wide enough that the combination of the height and width makes the lower front corner of the fender an interference issue when turning the wheel. It also ends up being pretty darn close to the outside of the fender, but you can’t add much more backspace on the wheel with a 15” because of brake/suspension clearance. It’s been done of course but body tolerances and ride height make it a car to car kind of thing.

Usually for the front a 225/60/15 is about as big as you want to go with a 15x7 and a 4.25” backspace on the 73+ disks. Especially with a ‘71, sometime in ‘72 they made the wheel opening longer so after that the lower front corner clearance is less of an issue.

 

[Pious_Paladin]

Not likely. The problem gets to be the height, a 235/60/15 is over 26” tall and is wide enough that the combination of the height and width makes the lower front corner of the fender an interference issue when turning the wheel. It also ends up being pretty darn close to the outside of the fender, but you can’t add much more backspace on the wheel with a 15” because of brake/suspension clearance. It’s been done of course but body tolerances and ride height make it a car to car kind of thing.

Usually for the front a 225/60/15 is about as big as you want to go with a 15x7 and a 4.25” backspace on the 73+ disks. Especially with a ‘71, sometime in ‘72 they made the wheel opening longer so after that the lower front corner clearance is less of an issue.

Excellent info! Thank you so much, you have made my life significantly easier!