Trying to underdstand backspacing and offset

blk-4runner

blk-4runner

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looking thru the search forum I still dont understand backspacing/offset but was wondering if this rim would fit into my 07 4runner, moto metal MO957 seem like it would fit with the right backspace of 4.53" but from the offset it seem to be at a high negitive 12mm.
 
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blk-4runner said:
looking thru the search forum I still dont understand backspacing/offset but was wondering if this rim would fit into my 07 4runner, moto metal MO957 seem like it would fit with the right backspace of 4.53" but from the offset it seem to be at a high negitive 12mm.
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WheelsFAQ-diagram.gif
 
Desert Fox said:
Great pictorial but does a negative offset mean the center of the wheel is left of the center line?
Click to expand...

Yes.

You dont really need to know backspace AND offset. They are both are different ways of measuring the same thing - where the wheel mounting pad sits in the wheel.

Basically pick one method and use it. Pretty much all aftermarket wheels will have offset and baskspace info available.
 
Can you guys try to help me out here? I've tried to understand this stuff, but it's hard for some reason. I have my stock wheels and 1.25" spidertrax. What offset do I have to get for aftermarket wheels to get the same effect?

Thanks

Jack
 
Anyone care to note stock offset and/or back spacing for stock 4th Gen wheels and stock FJ wheels? Seems like this thread won't be complete without it.

It's my understanding their are 4 stock 4runner options, correct?

1. 16" SR5 -5 spokes
2. 17" Sport -6 spokes
3. 18" Limited -5 spokes (look like the SR5s just bigger)
4. 18" Urban Runner -6 spokes (look like Sports just bigger

All are 9" width? Or are they 7.5"

FJ stock options (a common swap) are hard to track down but according to this They are all 17x7.5"

FJ Cruiser Specific 16"17" Wheel/Tire Fitment Guide - Toyota FJ Cruiser Forum

Ad it seems like increasing offset/backspacing with wheels and/or spidertrax doesn't necessarily resolve rubbing issues, it might just change where the rub occurs?
 
1. 16" SR5 -5 spokes
2. 17" Sport -6 spokes
3. 18" Limited -5 spokes (look like the SR5s just bigger)
4. 18" Urban Runner -6 spokes (look like Sports just bigger



^ Wrong. SR5 are 17" rims. Urban Runners are also 17" I believe. There is a 16" Rim that came on early 4th gen 4runners though.
 
I believe those SR5 5 spokes are 17" as well. The urban runners I have seen have the same 18" wheels as the limited, with 6 spokes. I think they are all 7.5" wide.

In response to your other question, the 18" limited wheels with 1.25" spidertrax should have an effective offset of -6.75mm.
 
17" Sport wheels have a +30mm offset
18" limited wheels have a +25mm offset
17" FJ cruiser wheels have a +15mm offset
 
I think a separate thread with a pic of the wheel and a measurement of backspace only would be a great sticky. I will pull my stocks out and also my TRD's and post a photo of each and the corresponding backspace. If we keep the thread limited to that it would be a great resource for anyone trying to work out the changes they can expect with different set-ups. If someone is getting a new set of wheels, take the time to accurately measure the back space and post it with a pic of the wheel and brief description of same. Will start the thread and post initial pics tomorrow along with a description of how and what is being measured so we can all compare apples to apples.
 
jdkilroy said:
I think a separate thread with a pic of the wheel and a measurement of backspace only would be a great sticky. If we keep the thread limited to that it would be a great resource for anyone trying to work out the changes they can expect with different set-ups. If someone is getting a new set of wheels, take the time to accurately measure the back space and post it with a pic of the wheel and brief description of same. Will start the thread and post initial pics tomorrow along with a description of how and what is being measured so we can all compare apples to apples.
Click to expand...

I've been looking all over for exactly that!

Or even a excel chart showing stock measurements vs aftermarket sizing with the amount that it moves out over stock!
 
knightsfs4 said:
Can you guys try to help me out here? I've tried to understand this stuff, but it's hard for some reason. I have my stock wheels and 1.25" spidertrax. What offset do I have to get for aftermarket wheels to get the same effect?

Thanks

Jack
Click to expand...

Im with him... I have 17" stock rims with 1.25 spacers. Im running 285/70r17 BFG KOs. What offset will I need if I go aftermarket? Staying with a 17x8in wheel.
 
4RunnerB4 said:
Im with him... I have 17" stock rims with 1.25 spacers. Im running 285/70r17 BFG KOs. What offset will I need if I go aftermarket? Staying with a 17x8in wheel.
Click to expand...

Check out Tire Rack for tire/ wheel info

Wheel offset and backspace measure the same thing but in a little different way. They tell you where in the wheel well a particular wheel will sit.

Offset is a measurement in millimeters from the backside of the mounting plate to the center line of the wheel. A positive number puts the mounting plate further away from the backside of the rim. A negative measurement moves it closer to the backside. Since offset is based on the center line, the width does factor in. That is to say an 8-inch wide +45mm offset and 7-inch wide +45mm offset results in a 1/2" difference in wheel positioning. The 8-inch wide will be further into the wheel well. To gain a better understanding of the offset of a wheel, read our tech article on this topic.

Backspace measures the distance from the mounting plate to the back edge of the wheel. The higher the backspace the further into the fender well it will sit.
 
boondoggle said:
Anyone care to note stock offset and/or back spacing for stock 4th Gen wheels and stock FJ wheels? Seems like this thread won't be complete without it.

It's my understanding their are 4 stock 4runner options, correct?

1. 16" SR5 -5 spokes
2. 17" Sport -6 spokes
3. 18" Limited -5 spokes (look like the SR5s just bigger)
4. 18" Urban Runner -6 spokes (look like Sports just bigger

All are 9" width? Or are they 7.5"

FJ stock options (a common swap) are hard to track down but according to this They are all 17x7.5"

FJ Cruiser Specific 16"17" Wheel/Tire Fitment Guide - Toyota FJ Cruiser Forum

Ad it seems like increasing offset/backspacing with wheels and/or spidertrax doesn't necessarily resolve rubbing issues, it might just change where the rub occurs?
Click to expand...


The stock or standard backspacing for the 17x7.5 rims is 5 inches.

adding wheel spacers and or decreasing back spacing gives room between your upper control arm and the inside side wall of your tire as well as increase the distance between when your tire is fully turned and the body mount just behind the front tires (for installing wider tires). This modification does alleviate tires rubbing the UCA; however you are correct it doesnt resolve rubbing issues between your tire and any fender contact points.

For what its worth.. I'm running a 16x8 rim with a 4.25" back spacing. This would be equivalent to a factory rim spaced out with a 3/4"-1" spacer.

and as previously stated, you dont need to worry about offset if you know backspacing and vise-versa. If you know back spacing and you know how wide your rim is then you can figure the offset.

If you know the offset and you know the width of your rim you can figure the backspacing

16x8 rim with 4.25 backspacing = .25" positive offset.

17x7.5 rim(stock) with 5" backspacing = -2.5" offset

so the stock wheel center sits 2.5" behind the hub face. This gives the hub bearings there maximum load rating.

On a side note the further away the center of the tire is from the hub face, the lower the hub bearing load rating becomes.
 
knightsfs4 said:
Can you guys try to help me out here? I've tried to understand this stuff, but it's hard for some reason. I have my stock wheels and 1.25" spidertrax. What offset do I have to get for aftermarket wheels to get the same effect?

Thanks

Jack
Click to expand...

4RunnerB4 said:
Im with him... I have 17" stock rims with 1.25 spacers. Im running 285/70r17 BFG KOs. What offset will I need if I go aftermarket? Staying with a 17x8in wheel.
Click to expand...

any ideas to these questions...im in the same boat.
 
a 3.5" backspacing on a 7.5 inch wide rim would be equivalent to factory rim on 1.5" spacer

a 3.75 backspacing on a 7.5 inch wide rim would be equivalent to a factory rim with 1.25in spacer

a 3.25" back spacing on an 8" wide rim would also be equivalent to factory rim with 1.5" spacer

and a 3.5" back spacing with an 8" wide rim would be the equivalent to a factory rim with a 1.25" spacer

P.S. happy hunting to you to find a rim with an backspacing less than 4.25 for a toyota 6 x 5.5 bolt hub
 
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