10 inch rims and backspacing

keel5 · Feb 19, 2005

I know this post is like beating a dead horse.

I am going to order some 33x12.5x15 Goodyear MT/Rs and some 10 inch wheels. Here in NJ I have to go through a stability test for inspection. The last time I went I almost failed. The guy doing the test told me that if I had 10in wheels instead of 8in I would have had no problem passing.

Here is my question. With the 10in rim will the tire stick out any more then with a 8in rim? I'm talking about the tire tread. Am I right in thinking that the backspacing is the same no matter what width rim I go with? So, with that I should be ok with 3.75 or 4 inch backspacing?

Thanks!

BillR · Feb 19, 2005

keel5 said:
I know this post is like beating a dead horse.

I am going to order some 33x12.5x15 Goodyear MT/Rs and some 10 inch wheels. Here in NJ I have to go through a stability test for inspection. The last time I went I almost failed. The guy doing the test told me that if I had 10in wheels instead of 8in I would have had no problem passing.

Here is my question. With the 10in rim will the tire stick out any more then with a 8in rim? I'm talking about the tire tread. Am I right in thinking that the backspacing is the same no matter what width rim I go with? So, with that I should be ok with 3.75 or 4 inch backspacing?

Thanks!

If an 8" wheel and a 10" wheel both have 4" of BS, then the tires would stick out 2" more on each side with the 10" rim. Remember, BS is the distance between the WMS and the inner rim. So if that distance is the same, and the rim is wider, then the added width is all on the outside. Actually, most 10" wheels have less than a 4" BS. Most are around 3 5/8" -3 3/4" or so. This makes the tire stick out even more.

BrettM · Feb 19, 2005

actually that's wrong Bill. the wheel will stick out 2 inches farther, but the tire tread will only be 1 inch farther out. it's like adding a 2 inch longer shackle; you only gain half the amount.

BillR · Feb 19, 2005

BrettM said:
actually that's wrong Bill. the wheel will stick out 2 inches farther, but the tire tread will only be 1 inch farther out. it's like adding a 2 inch longer shackle; you only gain half the amount.

I gotta disagree Brett. It's not like a shackle. If the wheel is wider on the front side only, then the tire is only wider there also. To get some of the tread width on the backside of the wheel, you'd have to have more backspace.
NOW, if we're talking about putting a 12.50 tire vs. a 10.50 tire on the SAME wheel, then your analogy would be correct and half of the tread width WOULD be on the backside.

EDIT- Brett IS correct. My bad!

BrettM · Feb 19, 2005

the tread is going to sit centered over the center of the wheel. by adding 2 inches to the outside of the wheel you only move the center of the wheel out by 1 inch.

MaXJohnson · Feb 19, 2005

Let me know when the voting starts so I can give Brett my vote

BillR · Feb 19, 2005

BrettM said:
the tread is going to sit centered over the center of the wheel. by adding 2 inches to the outside of the wheel you only move the center of the wheel out by 1 inch.

Hmmm...
I believe you're right! :lecture:
Thanks for the explaination. That clears it up.
So the wheel would stick 2" further out, but the tread ony 1". That's also a reason that the rim's not protected as much with a 10" wheel.
Thanks Brett!

keel5 · Feb 19, 2005

BrettM said:
the tread is going to sit centered over the center of the wheel. by adding 2 inches to the outside of the wheel you only move the center of the wheel out by 1 inch.

That is exactly what I was thinking. Now, is the 10in wheel going to make the tire side wall inflate more? If so will I need more backspacing?

BrettM · Feb 19, 2005

hey, no problem, I'm glad I was clear. it can be kinda confusing figuring that out.

also, the tire at the bead is 2 inches wider, but only 1 inch wider at the tread, so that means the widest part of the buldge will be about 1.5 inches wider on a 15x10 rather than 15x8.

10 inch rims and backspacing

keel5

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BillR

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BrettM

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BillR

Toy Jeep driver!

BrettM

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MaXJohnson

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BillR

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keel5

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BrettM

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