Wheel offset and backspacing

[Louisiana Overland]

first, forgive me for being 50 and not understanding this. I am considering aftermarket wheels. I had bought spacers but never installed for fear of a weak link and over stressing wheel bearings etc. so when I buy wheels, Id like for them to have the correct offset or backspace to push the wheel out some. I have a 3” lift and run 285/70 BFGs. What am I looking for on backspace/offset?

 

[Dave 41079]

Wheel width becomes a factor too.

For example, a 17x8 with a 4.5" BS will have a 0 offset and 4.5" sticking out from the hub face.

However, a 17x9 with a 4.5" BS will have a -25 offset and 5.5" sticking out from the hub face.

If the 17x9 had a 0 offset, then it would have a 5" BS and 5" sticking out from the hub face.

To get your BS, take your width and add an inch to it. Divide that number by two. That is your wheel's centerline. The next part is where it gets tricky because you have to convert mm to inches. Take your offset and divide it by 25.4 and that will give you the same number in inches. If the offset is negative, subtract it from your centerline...positive, add to your centerline. That gives you your backspace.

If you take your wheel width and add one inch, then subtract the backspace, that will give you the distance the wheel will stick out from the hub.

Now that I've :deadhorse:

A 17x8.5 with a -10 offset should get you pretty close to flush with the fender flare on a 285.

Then again...tire sizes vary by make and model...

 

[JohnTheLuck]

Maybe this little app could help your understanding. I did it for me:

https://www.1010tires.com/Tools/Wheel-Offset-Calculator#

 

[Bossman]

This is a helpful thread to review:

http://www.toyota-4runner.org/5th-gen-t4rs/156378-going-bigger-5th-gen-tire-fitment-guide.html

 

[Louisiana Overland]

A 17x8.5 with a -10 offset should get you pretty close to flush with the fender flare on a 285.

Then again...tire sizes vary by make and model...

I am looking at a wheel made by SCS
8.5” wide 4.3” backspace, -10 offset

Another made by Icon
8.5” wide 4.75” backspace, offset = 0

What would be the difference in how these look in relation to the flare and would either cause me to do a BMC?

 

[FattyHunter]

It depends on tires too, I used to have the stealth 6 17x8.5 -10mm 4.30 bs, running 285 ko2, it's almost flush with fender. Then I ran the same wheels with 295 STT Pro, then it sticks out a little bit. Then I got the F5 17x9 -38mm 3.5 bs running 295 STT Pro, it's perfect for me.

 

[Dave 41079]

I am looking at a wheel made by SCS
8.5” wide 4.3” backspace, -10 offset

Another made by Icon
8.5” wide 4.75” backspace, offset = 0

What would be the difference in how these look in relation to the flare and would either cause me to do a BMC?

The Icon would sit inboard an additional .45" compared to the SCS. Tires matter too. As far as a body mount chop is concerned, that will also depend on your alignment.

 

[Dadlevel1000]

New memeber new 5th gen

TI too am completely with out knowledge in this dept. What off set can I run with a leveling kit and pretty much stock tires and not have to do any cutting to avoid rubbing. Thank you I’m advance. I am looking at 17x9 with a 0 mm offset. But what size rim and offset will allow me to turn without rubbing and also drive over shit without hitting the fender

 

[emmantik]

TI too am completely with out knowledge in this dept. What off set can I run with a leveling kit and pretty much stock tires and not have to do any cutting to avoid rubbing. Thank you I’m advance. I am looking at 17x9 with a 0 mm offset. But what size rim and offset will allow me to turn without rubbing and also drive over shit without hitting the fender

You might rub a bit with that size. I only have a 1" front level, my wheels are 17x8.5 0 offset. I only rub on the mud flap (very minimally) when reversing at full lock on a incline. I run stock size Falken Wildpeak AT3. Since it is very minimal rub I have not made any modifications. Since you will stick out a but more at 9" width you may rub a bit on the fender liner or mudflaps.

Before I upgraded my wheels, I measured spacing between tires and liner/mudflaps when steering wheel was at complete steering lock both left and right side. This would give me an idea of spacing I would have and would help me decide what size wheels to go with. I also used this site which also helped a lot.

Alloy Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit

 

[Captain Spalding]

TI too am completely with out knowledge in this dept. What off set can I run with a leveling kit and pretty much stock tires and not have to do any cutting to avoid rubbing. Thank you I’m advance. I am looking at 17x9 with a 0 mm offset. But what size rim and offset will allow me to turn without rubbing and also drive over shit without hitting the fender

TRD Pro’s with +4 mm offset and stock size tires require cutting. So the 0 mm offset wheels wil require cutting too.

Pasted from elsewhere:

When you widen the track of your vehicle with either wheel spacers or changes in offset you increase the scrub radius. The scrub radius is the distance between the center of the tire and the point where the steering axis meets the ground. Increasing the scrub radius contributes to an increased arc prescribed by the wheel as it turns, and it’s the increased arc, primarily, that causes the rubbing.

This is a (mostly accurate) scale drawing of the 4Runner front susension. As the label denotes, it shows a stock 265/70r17 tire on a 7½x17 rim with a +15mm offset. Take note of the scrub radius at the bottom of the drawing:

What if we replace the stock wheel with the very popular 285 tire on the 7x17 rim with the +4mm offset?

Comparing the two drawings, notice in the second drawing that the offset is decreased and the scrub radius has increased.

Looking down from the top, we still see the dashed line prescribing the steering axis. From this view it is apparent that not only is the point of the tire’s rotation on the ground not centered on the tire laterally, it’s not centered front to back either. An effect of this is that as the tire is turned left and right, the leading outboard corner and the trailing outboard corner of the tire prescribe 2 different arcs, drawn in orange.

Now let’s swap out the 265 wheel for the 285.

The arc of the 285 wheel is purple. The arc of the 265 wheel is orange. The 285 wheel fits in the wheel well just fine. So why does it rub? Because the 4Runner is not very tolerant to changes in the diameter of this arc. It’s so intolerant, in fact that just pushing the wheel outboard of the steering axis a scant 4 tenths of an inch, (as occurs when the TRD Pro rims are fitted) causes Toyota to cut the fender at the port. It’s not merely the wheel being pushed outboard that causes the rubbing. It’s the wheel being pushed away from the steering axis that causes the trouble.