Wheel width vs offset

Hello everyone! How does the wheel width affect your offset and vice versa? Currently running 285s with a +5 offset, 8.5" wide, TRD Pro replica rim. I am very close to the UCA at full lock and like to move away from the UCA and looking at a 9" rim with 0 offset. Will the 1/2" of extra width of the wheel negate the 5mm of negative offset?

 

To your question. It will be worse. The inner bead will be even farther inside on the 9" 0 offset. Go with 8.5" wide 0 offset like a Method bead grip series wheels.

 

Check out @SCSPerformance wheels as well, they originally only made wheels for Tacomas and 4 runners. Designed for bigger tires, you can check out their specs
I have 8.5 wide wheels with -10 offset and 285s, lots of room to the ucas.

 

Offset refers to the wheel/hub mounting surface's position relative to the centerline of the wheel. Positive offset means the surface is outward from the wheel's centerline (which brings the wheel closer to the center of the vehicle), negative offset is inward (pushing the wheel farther from the center of the vehicle). Offset can be combined with the wheel width to calculate backspace, which refers to the wheel/hub mounting surface's position relative to the inner edge of the rim.



It sounds like you're concerned about backspace. If you have too much backspace, the wheel will contact suspension components--most likely the upper control arm.

If you increase wheel width without changing offset, you also increase backspace. If you increase wheel width while maintaining the same backspace, you reduce offset.

Given any two values of offset/backspace/wheel width you can calculate the third value, assuming you paid attention in algebra.

BS = ((WW + 1) / 2) + (ET / 25.4)

BS is backspace
WW is wheel width. This is measured at the bead, so add 1" to account for the flanges.
Divide by 2 to get the center of the wheel.
ET is offset, which is in millimeters. Divide by 25.4 to convert to inches.

If you don't want to do the math by hand you can use an online calculator, or get approximate conversions using a lookup table. I just found this lookup table via Google Image Search.



An 8.5" wide rim with +5mm offset has 4.95" backspace (closest approximation is +6mm/5.0" using the table).
A 9" wide rim with 0mm offset also has 5.0" backspace.

So your wheel will move slightly inboard (and closer to the UCA) but it shouldn't be a problem unless you're practically touching it already.

Keep in mind that UCA contact isn't the only concern when fitting wider wheels or wider/taller tires. Too little offset (or excessive negative offset) can cause the wheel to rub the frame, mud flaps, or inner fender/cab mount.

More on that here: https://www.youtube.com/watch?v=LAYGdcKSA3o

 

Thank you for all of the replies guys. I really appreciate it. I think I will be going with the TRD wheels in the SEMA style 17x7”. These are essentially the same offset as my current wheels at +4, but the narrower width should gain me extra clearance at my UCA, correct?

 

I have been reading from a distance and I'm not sure of the end game here. If you have say a 1/4" or 6mm UCA clearance through full turn range, it should be good.

You say you have 285 tires, so you really don't want to drop to 7" wide rims. For those, you'd want a 255 skinny tire, which of course would eliminate the tire closeness to your UCA by tire dimension alone.

If this is just about UCA gap on current setup, a BORA 10mm spacer with longer lug bolts is cheaper than 4 new wheels at the wrong size for 285 tires. Or skip spacers and get min 8" wheels with more negative offset.

 

Yes, the MFGs usually recommend a 7.5 rim at 285, but there are many in here running 285s on 7” rims, so I’m hoping it’ll be fine.