Sorry for beating a dead horse about tire size

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Yerk

Yerk

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Going to apologize first if this is screwed up. I just signed up and have not figured out how this works yet. I seen a old post by Old Man Mopar about fitting a 275/60/15 under the rear of your Duster. I'm wanting the same set up but have a question about the spacer. From what I have read it looks like a 15x8 with 4.25 BS is the wheel I need. I do want to set the back of the car down on top of the tire but cant find anyone that says the tire clears up top. This is my first Mopar so I'm learning as I go. I called Mancini on the spacer as recommended but they had no idea what I was talking about. Hope this gets to you or someone who can help. Thanks!!
 
Yerk said:
Going to apologize first if this is screwed up. I just signed up and have not figured out how this works yet. I seen a old post by Old Man Mopar about fitting a 275/60/15 under the rear of your Duster. I'm wanting the same set up but have a question about the spacer. From what I have read it looks like a 15x8 with 4.25 BS is the wheel I need. I do want to set the back of the car down on top of the tire but cant find anyone that says the tire clears up top. This is my first Mopar so I'm learning as I go. I called Mancini on the spacer as recommended but they had no idea what I was talking about. Hope this gets to you or someone who can help. Thanks!!
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Here is the original post
1/4" spacer 275/60
 
Here's a shout-out to Old Man Mopar. He will get a ping on his email and can get in touch with you for your questions.

@Old Man Mopar
 
An 8" rim in the 275 is a bit narrow for cornering, like with a street car..
For long tread life, you will have to drop the tire pressure to get the tread flat, so you don't burn off the centers.This is fine in a straight line. But if or when you get down to 24psi, the car corners kindof funny. The tires roll over onto the sidewalls and the inside tread barely has any pressure on it, and the back of the car heels over like a ship at sea. This causes the back of the car to steer to the outside of the turn, and if you come in to the turn too hot and are not ready for it... there is a good chance that with gas applied,you will spin out of control. So practice first, on a deserted parking lot, with no cops around.
8.5s are a lil better,
but those tires really want 9.2s, which there is no such thing... but there are 9s and 10s available.
I used the 8.5s and just lived with it, until I got my 295 on 10s combo worked out. Which the 10s are still too narrow, but I got to liking the roll-over, at the no more than 24psi, that I have to run, and the 294s have enough sideways rubber that I no longer spin out...
 
AJ/FormS said:
An 8" rim in the 275 is a bit narrow for cornering, like with a street car..
For long tread life, you will have to drop the tire pressure to get the tread flat, so you don't burn off the centers.This is fine in a straight line. But if or when you get down to 24psi, the car corners kindof funny. The tires roll over onto the sidewalls and the inside tread barely has any pressure on it, and the back of the car heels over like a ship at sea. This causes the back of the car to steer to the outside of the turn, and if you come in to the turn too hot and are not ready for it... there is a good chance that with gas applied,you will spin out of control. So practice first, on a deserted parking lot, with no cops around.
8.5s are a lil better,
but those tires really want 9.2s, which there is no such thing... but there are 9s and 10s available.
I used the 8.5s and just lived with it, until I got my 295 on 10s combo worked out. Which the 10s are still too narrow, but I got to liking the roll-over, at the no more than 24psi, that I have to run, and the 294s have enough sideways rubber that I no longer spin out...
Click to expand...
I only go straight A to B, red light to red light so cornering is not an issue.
AJ/FormS said:
An 8" rim in the 275 is a bit narrow for cornering, like with a street car..
For long tread life, you will have to drop the tire pressure to get the tread flat, so you don't burn off the centers.This is fine in a straight line. But if or when you get down to 24psi, the car corners kindof funny. The tires roll over onto the sidewalls and the inside tread barely has any pressure on it, and the back of the car heels over like a ship at sea. This causes the back of the car to steer to the outside of the turn, and if you come in to the turn too hot and are not ready for it... there is a good chance that with gas applied,you will spin out of control. So practice first, on a deserted parking lot, with no cops around.
8.5s are a lil better,
but those tires really want 9.2s, which there is no such thing... but there are 9s and 10s available.
I used the 8.5s and just lived with it, until I got my 295 on 10s combo worked out. Which the 10s are still too narrow, but I got to liking the roll-over, at the no more than 24psi, that I have to run, and the 294s have enough sideways rubber that I no longer spin out...
Click to expand...
WOW! Thank for the reply but red light to red light is more my speed.
 
Just remember what might happen when you have to avoid an accident. It may not have been your fault that that other guy came into your space. But that thought won't comfort you when your classic car becomes a write-off.
Practice anyway.
just saying
 
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Most cars I see with fat rear tires have the jacked-up stinkbug stance. If you want it to sit low you have to center the tire in the well, meaning you have to have the right backspace for the wheel width. For example, say your current 4.5" wide wheel is perfectly centered, and it has 3-inch backspacing. If you go to an 8.5 inch wheel, you want it to fit so that it extends 2 inches further to the outside and two inches further inside, so add 2 inches to the backspacing — you need 5-inch backspace. Note that this is a hypothetical example — do not refer to these specific numbers. It may also be true that 1/4 to 1/2-inch either way doesn't matter, depending on your tire width.
 
Yes sir I agree. I have basically Have the same car as Old Man MOPAR, color, etc. so just wanting to reach out to see what he done. He looks like he has it figured out with the right ride height and tire size. If anyone knows him would you please have him contact me, his in box is full. Thanks for all the input, I do appreciate it.
 
What backspace you need really depends on what rear axle you have. The A-body rear axle housings are NOT all the same size. A-body 8 3/4's are wider than the A-body 7.25's and 8.25's, and even the 8 3/4's are different depending on whether you have BBP or SBP axles or not.

With a 15x8, 4.25" backspace would only work with a 7.25/8.25 unless they car is really jacked up in the back. 275's are the widest tire you can fit with the stock spring locations and untrimmed quarters, assuming you want the tires to actually fit inside the wheel wells. If you like the '70's "street freak" style with the rear end jacked up in the air and tires hanging out like a 4x4, it doesn't matter. But if you want them inside the quarter lips you have to get the backspacing right.
 
Yerk - depend on 72bluNblu - he knows his tires/rims combinations. He helped me a bunch with my 73 Sport with relocated springs.
 
I know this is a dump question but keep in mind this is my first Mopar. How do I know what rear end I have. I just got this car yesterday, it’s a 72 duster 340 clone. Have not verified it has a 340 or a 318, it is a 4 speed car from the factory.
 
Guess I need to add, I don’t want the car jacked up in the rear. I like em stuffed full of Tire and dragging the ground.
 
Here's one chart I've run across. Picture are not perfect but you should be able to figure out which one you have.
rearspotter.jpg
 
Here’s what the 275/60/15 look on a set of 15x9’s with a 4.5” backspace. I have an 8.8 rear with the 1/2” doctor diff spring relocation I know it’s a barracuda. But just to give some ideas.
DB28CC2B-36DF-49E1-B8A4-3BDB097DA81E.jpeg
E9EFF489-0440-4F9C-B2C5-04C257BE83BD.jpeg
 
66fyssh said:
Here's one chart I've run across. Picture are not perfect but you should be able to figure out which one you have.
View attachment 1715434098
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Now we are cooking with grease. Visual aid, I like it. I have a 7 1/4 so sounds like the 275 on a 8’’ wheel with 4 1/4 BS will work. Right? If so back to 2 of the original questions. The spacer? Do I need to do that and how much room will I have from the top of the tire to the top of the wheel well? Thanks 66fyssh! Appreciate the info, I’ll hang on to that.
 
Thanks for the pics of the tires and wheels. I’ve always owned chevelles, Camaros, etc. you can shove a 275 on a 7” rally on about any Chevrolet. This car seems to be a little more difficult. It currently has rinky dink 14’ wheels that just want work for me. I also didn’t realize the lack of wheels with the small bolt Pattern. So looks like a 15’ mopar rally will go back on it which I’m okay with. Just wish I could get some made that are 15x4’s for the front. Googled it to death with no luck. Any ideas?
 
Yerk said:
Now we are cooking with grease. Visual aid, I like it. I have a 7 1/4 so sounds like the 275 on a 8’’ wheel with 4 1/4 BS will work. Right? If so back to 2 of the original questions. The spacer? Do I need to do that and how much room will I have from the top of the tire to the top of the wheel well? Thanks 66fyssh! Appreciate the info, I’ll hang on to that.
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If it has a 7.25 and a 340 and you put a set of 275's on there you can probably measure the life of that rear axle in hours. One good launch and that extra tire will probably dump the rear axle guts right in the street.

With a 15x8 and a 4.25" backspace you should be pretty close to the right spot with a 7.25". If you need a wheel spacer it will be a small one, 1/8" at most. I would mount up the wheels first, then see if you need anything at all. As for the distance from the top of the tire to the wheel well, that will depend on what springs you have and how worn out they are.
 
72bluNblu said:
If it has a 7.25 and a 340 and you put a set of 275's on there you can probably measure the life of that rear axle in hours. One good launch and that extra tire will probably dump the rear axle guts right in the street.

With a 15x8 and a 4.25" backspace you should be pretty close to the right spot with a 7.25". If you need a wheel spacer it will be a small one, 1/8" at most. I would mount up the wheels first, then see if you need anything at all. As for the distance from the top of the tire to the wheel well, that will depend on what springs you have and how worn out they are.
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Thanks brother, greatly appreciated! Many thanks to all for you input.
 
One last thing and I will leave you gentlemen alone. If you have any leads on where to get wheels that’s my next step. I’ve called Stockton wheel co but they have not called back. I have the small bolt pattern. Thanks again.
 
You can get 15 x 4 in a steel wheel from Coker. In small bolt it is just , steel wheel only. They are rather pricey.
15 x 4 in small bolt , big bolt and cop wheels ( I have a pair of the cop wheels )

Frank
 
duster2 said:
You can get 15 x 4 in a steel wheel from Coker. In small bolt it is just , steel wheel only. They are rather pricey.
15 x 4 in small bolt , big bolt and cop wheels ( I have a pair of the cop wheels )

Frank
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Thank you sir!
 
Yerk said:
One last thing and I will leave you gentlemen alone. If you have any leads on where to get wheels that’s my next step. I’ve called Stockton wheel co but they have not called back. I have the small bolt pattern. Thanks again.
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[/QUOTE]

Wheel Vintiques. Directly or through Summit Racing.
 
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