Wheel backspacing question

[TJim]

Hello!

I have a 2004 TJ 2.4L 4-cylinder.

It came stock with: 215/70r15 (27”), on 15x7 steel rims with 5.5” backspacing (+38 offset)

Currently, I run: 235/70r16 (29”), on Rubicon Moab aluminum rims, 16x8 with 5” backspacing (+12 offset)

I want to run 31/10.5r15 tires, so I am searching for new rims. After research I understand that I have to buy some 15x8 aluminum rims.

My question is: How much backspacing should I get? And why?

 

[CodaMan]

This site can show you what you need to know:

https://tiresize.com/wheel-offset-calculator/

 

[CodaMan]

This chart may help as well:

 

[Jerry Bransford]

Forget you ever heard the term 'offset' where Jeep and truck wheels are concerned. Offset is more for car wheels.

For 31x10.50 tires you can run anything between 3.75" and 5" of backspacing, with the closer you can get to 5" the better but 4" being about as much as you'll find on an aftermarket aluminum wheel. 4" works very well for anything up to a 35x12.50 size but it's not easily found. For aftermarket aluminum wheels you're more likely to end up with 3.75 which works fine, it just protrudes out a bit more than a wheel with more backspacing would have.

Too much backspacing for wider tires causes the tires to rub on the suspension when the wheel is turned all the way right or left.

 

[TJim]

Forget you ever heard the term 'offset' where Jeep and truck wheels are concerned. Offset is more for car wheels.

For 31x10.50 tires you can run anything between 3.75" and 5" of backspacing, with the closer you can get to 5" the better but 4" being about as much as you'll find on an aftermarket aluminum wheel. 4" works very well for anything up to a 35x12.50 size but it's not easily found. For aftermarket aluminum wheels you're more likely to end up with 3.75 which works fine, it just protrudes out a bit more than a wheel with more backspacing would have.

Too much backspacing for wider tires causes the tires to rub on the suspension when the wheel is turned all the way right or left.

Thanks!

Do you believe that I am going to have any rubbing issues with 5" backspacing with 31x10.5 tires?
Is there any disadvantage by running 3.75" instead of 5"? Is there anything I should have in mind?

*I should mention that I am not likely to run bigger tires in the future.

 

[TJim]

This site can show you what you need to know:

https://tiresize.com/wheel-offset-calculator/

Thanks! nice link!

 

[Jerry Bransford]

Thanks!

Do you believe that I am going to have any rubbing issues with 5" backspacing with 31x10.5 tires?

If there is any it will be minor and only noticed when the steering wheel is turned all the way right or left. If that happens it is easily corrected by simply adding a washer under both steering stop bolts as described here... http://www.4x4xplor.com/steerstop.html

 

[LukesfirstJeep]

Do you believe that I am going to have any rubbing issues with 5" backspacing with 31x10.5 tires?

When I bought my Jeep, it had 31x10.5 Falken tires on wheels with 5.5" backspacing. I only got a light rubbing when I went full lock. If I had kept those wheels and tires, I would have added a washer, like Jerry B suggested.

 

[ToddDerrArtist]

I was worried that I may have issues with my factory Grizzly wheels, which are considered 5.5" backspacing and 15x7. It has been a non-issue. I did put two washers on the steering stop bolt and I have had no rubbing at all and no significant diminishment in turning radius that I can tell.

These are 31-10.50-15 BFG's and I wanted to maintain the tire under the flares. Including photos to hopefully illustrate.

Rear upper spring perch clearance on drivers side, which is the tightest since 1" lift springs do offset the rear axle just a smidge to the passenger side

No rubbing on front sway bar

No rubbing on front lower control arm

Two washers on steering stop cure all.

 

[Michigan TJ]

When I bought my 2003 X, it had 235/75R/15 tires on wheels that had 5.5” backspace. I didn’t like the wheels plus I wanted a little more aggressive look. I went with 31x10.5x15 tires on aluminum wheels with 3.75” backspace. Wheels are 15x8. My suspension is stock. I like the look and it rides and drives with no issues.

 

[Rubicon88]

3.75 BS is perfect for an 8" wide wheel.

It's the most diverse. Perfect for running 10.50 tires and it also allows you to run 12.50 tires should that day ever arise.

If you ever wish to sell them they'll be really easy to pedal.

 

[TJim]

Thanks everyone. I will come back with some 15x8 rim options!

 

[Rubicon88]

Thanks everyone. I will come back with some 15x8 rim options!

I've run these on several TJ's i owned and installed many for customer.

Look great...the finish holds up really well..pretty damn tough too

I don't know if these guys are sponsors and I'm not in bed with them other than a vendor of ours but here is a retail link to some 3.75 BS in 15x8

https://www.4wd.com/p/pro-comp-69-s...6!3!389350609662!!!u!293946777986!&s_kwcid=AL!{7836}!{3}!389350609662!!!u!293946777986!&ecmp=s:google&utm_source=google&utm_medium=cpc&utm_campaign=shopping&emlprox=out&ppcfon=1&gp=1&gclid=Cj0KCQiA1KiBBhCcARIsAPWqoSqHzRr7raqkrC83PXqotik3G_F3SaesULvRY8OvU-7USOhiALjSbHoaAhHMEALw_wcB

Just know the 3.75BS will be out past your flare but it's a small amount. It's not ignorantly out too far like some weird ass mall crawler.

The photo is with a 31x10.50x15

 

[Michigan TJ]

When I bought my 2003 X, it had 235/75R/15 tires on wheels that had 5.5” backspace. I didn’t like the wheels plus I wanted a little more aggressive look. I went with 31x10.5x15 tires on aluminum wheels with 3.75” backspace. Wheels are 15x8. My suspension is stock. I like the look and it rides and drives with no issues.

Here’s a couple pics.

 

[TJim]

I've run these on several TJ's i owned and installed many for customer.

Look great...the finish holds up really well..pretty damn tough too
View attachment 226623

I don't know if these guys are sponsors and I'm not in bed with them other than a vendor of ours but here is a retail link to some 3.75 BS in 15x8

https://www.4wd.com/p/pro-comp-69-s...6!3!389350609662!!!u!293946777986!&s_kwcid=AL!{7836}!{3}!389350609662!!!u!293946777986!&ecmp=s:google&utm_source=google&utm_medium=cpc&utm_campaign=shopping&emlprox=out&ppcfon=1&gp=1&gclid=Cj0KCQiA1KiBBhCcARIsAPWqoSqHzRr7raqkrC83PXqotik3G_F3SaesULvRY8OvU-7USOhiALjSbHoaAhHMEALw_wcB

Just know the 3.75BS will be out past your flare but it's a small amount. It's not ignorantly out too far like some weird ass mall crawler. View attachment 226626
View attachment 226628
The photo is with a 31x10.50x15

I think I found my next rims. Its more expensive here in Greece, but I think it is going to be worth it. Thanks