Rim Size VS offset VS backspace question(s)

[kapp_badbloodz]

Hello all,

I am sure these questions have been asked before but the search feature and google thrashing has yet to reveal the answers I desire.


So I am on the quest of searching the best fitment and functional rim setup possible. Since I am new to truck rim setups I have been doing a lot of converting and researching with more converting and yet even more researching which leads to more converting... its irritating as **** but I am getting there.

So the stock rim size (via the tire size chart) is a 17x7.5 with a backspace of 4.875" but it doesnt mention much about offset. I am sure an offset yields the desired backspacing required for specific tire specs. After some google thrashing I found some specs not sure how accurate they are. But I came to this specific measurement for the stock tire.

265/70R/17 on a 17x6 et 15 with a bolt pattern of 6x139.7


SO....

I start hunting for rims thinking I am good to go right...? WRONG! A LOT of the rims on the market (especially truck rims) are converted to inches rather than the traditional "mm" measurement that I was used to. The bolt pattern converts to:

6x139.7 = 6x5.5" with threads of M12x1.5


NOW...


Offset and backspacing.... how do I tie this all in? Ideally, I would like a 285/70R/17 with a little bit more wider stance (think slightly more poke). I would like to avoid using spacers on the hub to push the rim out more unless absolutely necessary. If the offset is really +15 what would be some aftermarket offsets that provide proper form and function? Would a -5 be pushing my limitations at all? Would that be ridiculous?

What about dropping rim size? Does this generally lead to any issues down the road? If I cant find the offsets or style rims I want what would stop me from getting a 16.5 or a 15 inch rim?

I am genuinely inexperienced with truck tires. I had a 400hp street car and could talk to earth's end about racing tires and slicks... just never had to deal with these conversions and deal with backspacing. Go on NASIOC and ask about backspacing and everyone will be like "huh" lol.

Thanks for the help and apologies for being long winded.

Corey

 

[WTERUNNER]

I just purchased a set of rims with a -10 offset and I've learned a stock size 265/70R17 BFG KO2 will rub with my setup. Not much but it will still rub. I'd say this is about the limit.

 

[LandCruiser]

Offset: distance of mount to centerline of wheel.

Backspacing: distance of mount to inside lip of wheel.

4runner takes 17" minimum, won't clear the brakes, otherwise.

 

[wfo9]

Its really simple.

Offset is distance off center line.

Given 8" wide rim and 0 offset. backspacing = 4.5". This reason for 4.5 vs 4.0 is that measured rim widths do not take the lip into account, so you always add 1" and divide by 2 to get the 0 offset backspacing. .

From there, negative offset will move the centerline inboard creating more track width, while positive will move it outboard. A -10 offset on a 8" rim will yield about 4.1 backspacing.

Ideal backspacing for these trucks is 4.5-4.0.

If you want the best possible fit on a 5th gen with the least amount of rubbing on a 285/70 17... Get a 17x8 0 offset wheel. The more negative offset the more chance of scrub angle rub and need for a body mount chop...

BTW, if you are looking for wheels here is a great guy to deal with https://www.fnwheels.com/

 

[flyrv9]

Look at any post by 1engineer. At the bottom there will be some cool links - one of which is a tire fitment guide that should cover your questions and more.

 

[jasonv]

that guide helps, but by no means "covers all questions".

I agree with above you should be looking for an 8 inch wheel with zero offset, which means it will have 4.5 inches of back spacing because an 8 inch wheel is really nine inches wide. (yes its stupid, wheels are always about an inch wider than what they are listed as)

once you start messing with offset, you will likely get rubbing even with stock wheel size

i had no lift, stock tire size (a bit bigger in diameter due to more aggressive tread) and 1.25 inch spacers (which is analogous to having some offset in the sense it changes the arc of the radius of a turn) and there was rub. add a 2 inch lift, still rub. switched to 17 X 8 wheels with no offset (which means 4.5 inch back spacing) without spacers and no rub.

 

[1engineer]

that guide helps, but by no means "covers all questions".

I agree with above you should be looking for an 8 inch wheel with zero offset, which means it will have 4.5 inches of back spacing because an 8 inch wheel is really nine inches wide. (yes its stupid, wheels are always about an inch wider than what they are listed as)

once you start messing with offset, you will likely get rubbing even with stock wheel size

i had no lift, stock tire size (a bit bigger in diameter due to more aggressive tread) and 1.25 inch spacers (which is analogous to having some offset in the sense it changes the arc of the radius of a turn) and there was rub. add a 2 inch lift, still rub. switched to 17 X 8 wheels with no offset (which means 4.5 inch back spacing) without spacers and no rub.

That's because that guide was designed to help people help themselves, not answer all questions.

"More aggressive tread" does not mean a larger diameter. Several aggressive tread tires have a smaller diameter than all season tires in the same size callout. Actual diameter is solely determined by the manufacturer, not the tread type.

On the 4Runners, moving your tires outboard, either through different offset wheels or with wheel spacers, increases your chances of rubbing incrementally with your spacing. Lifting does not help much, if at all.

 

[Jeremy556]

Another thing to be aware of - center bore. Toyota hubs are 106.1mm. You'll want wheels that have that size bore, or get hub rings to adapt a larger bore size down to 106.1mm.

Most aftermarket wheels are thicker than Toyota OEM wheels and the front wheel studs are short. Depending on your wheels, you may need extended thread lug nuts and/or replace the front wheel studs with longer ones. I did both and used the OEM rear studs, which are a few mm longer.

 

[WTERUNNER]

So here's a question, will the stock Dunlop 265/70R17 fit "properly" on a 8.5 inch rim. I'm emphasizing properly because I don't want the stretch look which is what I'm afraid may happen. Tread width on Tirerack for the tire is listed at 8 inches.

 

[1engineer]

So here's a question, will the stock Dunlop 265/70R17 fit "properly" on a 8.5 inch rim. I'm emphasizing properly because I don't want the stretch look which is what I'm afraid may happen. Tread width on Tirerack for the tire is listed at 8 inches.

Is that tread width or section width?

 

[WTERUNNER]

Is that tread width or section width?

Tread width, section width is 10.6

 

[1engineer]

Tread width, section width is 10.6

Then it will give you that stretch look!

 

[WTERUNNER]

Then it will give you that stretch look!

That's what I was afraid of. Need to run a larger tire size then. I'm thinking a 275 or possibly even a 285 series tire.

 

[jasonv]

That's because that guide was designed to help people help themselves, not answer all questions.

"More aggressive tread" does not mean a larger diameter. Several aggressive tread tires have a smaller diameter than all season tires in the same size callout. Actual diameter is solely determined by the manufacturer, not the tread type.

On the 4Runners, moving your tires outboard, either through different offset wheels or with wheel spacers, increases your chances of rubbing incrementally with your spacing. Lifting does not help much, if at all.

i was directly responding to the other guy, who referred to it as "answering all questions". but thanks for clearing that up.

and yes a more aggressive tread on a similar spec'd tire CAN mean it will rub as opposed to a less aggressive tire. thats blatantly obvious, and the direct experience of anyone who has ever put a more aggressively treaded tire on their rig. does it mean it always will, or that the aggressive tread pushes you into a different size tire? of course not but sometimes rubbing is a matter of mm's, or /16ths of an inch)

you truly are insufferable

 

[1engineer]

i was directly responding to the other guy, who referred to it as "answering all questions". but thanks for clearing that up.

and yes a more aggressive tread on a similar spec'd tire CAN mean it will rub as opposed to a less aggressive tire. thats blatantly obvious, and the direct experience of anyone who has ever put a more aggressively treaded tire on their rig. does it mean it always will, or that the aggressive tread pushes you into a different size tire? of course not but sometimes rubbing is a matter of mm's, or /16ths of an inch)

you truly are insufferable

First, the guy said "all your questions" which is quite different than "all questions."

Even though your opinion of me is not the highest I don't want you going through life thinking something is true when it is not. So for your edification I spent 30 seconds and went to Tire Rack, picked out four random tires of differing treads in the stock 4Runner size and compared them. You will see that IT DOES NOT MATTER what type of tread the tire has in determining what the O.D. will be. There is no rhyme or reason! You can be rubbing with an All Season tire and put an aggressive tread tire on there and not rub. If you pick four different tires from four different manufacturers you will get different results! What really boggles the mind is a specific tire will be larger than the others in one size (265) and that same tire will be smaller than the others in a 285 size! That's why the guide is so general and people need to do their own research instead of reading posts like yours that will steer them in the wrong direction. Look at the pics below.

 

[WTERUNNER]

First, the guy said "all your questions" which is quite different than "all questions."

Even though your opinion of me is not the highest I don't want you going through life thinking something is true when it is not. So for your edification I spent 30 seconds and went to Tire Rack, picked out four random tires of differing treads in the stock 4Runner size and compared them. You will see that IT DOES NOT MATTER what type of tread the tire has in determining what the O.D. will be. There is no rhyme or reason! You can be rubbing with an All Season tire and put an aggressive tread tire on there and not rub. If you pick four different tires from four different manufacturers you will get different results! What really boggles the mind is a specific tire will be larger than the others in one size (265) and that same tire will be smaller than the others in a 285 size! That's why the guide is so general and people need to do their own research instead of reading posts like yours that will steer them in the wrong direction. Look at the pics below.

I'm trying to stay out of this argument but the information you provided is applicable to my current issue. A couple of forum members who have the Stealth 6 wheel and are running the BFG KO2 in the stock size have had issues with rubbing. How bad I'm not sure. I'm 100% sure that this is mostly due to the -10 offset. Using the info you posted I'm assuming (we all know what that means) that if I choose a tire with a diameter less than 31.6 inches I can lessen the amount of rubbing or trimming I'm going to have to do.

Thanks!
Jim

 

[1engineer]

I'm trying to stay out of this argument but the information you provided is applicable to my current issue. A couple of forum members who have the Stealth 6 wheel and are running the BFG KO2 in the stock size have had issues with rubbing. How bad I'm not sure. I'm 100% sure that this is mostly due to the -10 offset. Using the info you posted I'm assuming (we all know what that means) that if I choose a tire with a diameter less than 31.6 inches I can lessen the amount of rubbing or trimming I'm going to have to do.

Thanks!
Jim

Correct.

 

[kapp_badbloodz]

Look at any post by 1engineer. At the bottom there will be some cool links - one of which is a tire fitment guide that should cover your questions and more.

Check the tire guide. Didn't have anything on offset/backspace/etc

Thanks for the info on 16" rims. What about 16.5s and a little tire stretch?

 

[WTERUNNER]

Check the tire guide. Didn't have anything on offset/backspace/etc

Thanks for the info on 16" rims. What about 16.5s and a little tire stretch?

Need a 17 inch wheel to clear the brakes

 

[ChloroFiend]

Didn't see this mentioned in the thread (or in 1Engineer's wicked link)...

Say i wanted to throw on some of those 8" wide rims from like FM Wheels, while retaining the stock rubber. Is it likely I'll run into rubbing issues with that? Does wheel width have as much to do with clearance issues as overall diameter?