Wheel questions

Dumb guy questions

When a wheel has an offset does that mean it sticks out farther than a 0 offset? Is the purpose af an offset to fix rubbing issues?

What does backset mean?

What difference does it make if a wheel is 9” wide compared to 7”? Will this make the tire wider and shorter?
Thanks

 

They're round and they roll.... what more do you want to know?

Seriously though.... Offset is related to the bolting surface relative to the centerline for the wheel.
Negative offset moves closer inward, positive offset moves further outward.
Backset is the total distance from inner rim edge to bolting surface.
Wheel widths are related to the rim width from inner to outer bead lip. the wider the width, the wider the tread that can be supported (first number in tire ratios). If you use a narrow wheel with a wide tire, or a wide wheel with a narrow tire, you risk tire bead related failures (flat/failed tire). This would be more pronounced when airing down for offroad.

Hope that helps and I'm sure others will chime in.

 

Just so people don't get confused and second guess themselves like I just did...

Negative offset (or a larger backspace) moves the TIRE further owtwards.

@NoOne said it correct, just in a slightly confusing way for someone who is trying to learn.

I have a -12mm offset on a 9" wide wheel to provide clearence. Otherwise my tire would rub my UCA (it still does a little bit) . This also caused the tire to rub the body and front bumper more. Those things can be trimmed, UCA's cannot be trimmed.

 

Negative offset = less backspace, not “larger”

 

the lower your offset is the more it will push your wheels out further pass the fender.

 

If your head isn't already spinning, let me toss this out there:

Remember that backspacing is measured based on the overall width of the wheel. For example, a 16X7 wheel is actually 8" wide at it's outer edges. So, a zero offset wheel would be 4" of backspacing to the rear, and 4" to the front. If you move to a 16X8, which is 9" wide, with zero backspacing, then you've added another 1/2" to both the front and rear. The safest thing to do is measure possible contact points (control arms, fenderwell liners, etc.) based on what you have on your truck now, get the specs on your current setup, then look at the backspacing available on various wheels you're interested in.

Clear as mud, right?

 

Yep... I was just about to point out that you can’t compare a 7” to a 9” wheel... because now you have to account for the extra overhang. Also, moving offset can create issues with inner wheel components such as calipers, rotors, control arms, steering knuckles, etc. look at the photo I provided above and you can see how the spokes vary to accommodate the offset.

There is a whole wealth of information on what has been tried here... probably best to take advantage of that. It sure beats expensive mistakes. Craigslist is full of those....

 

[(rim width + 1")/2] + (- or + offset)

Example;
16"x8" et -12mm
[(8+1)/2] + (-12mm)
4.5" - 12mm
4" backspace

17x9 et +12mm
[(9+1)/2] + (+12mm)
5" + 12mm
5.5" backspace


Or...




Here's a calculator you can play with to visualize. Caveat: This calculator fails to use wheel width instead of rim width to calculate backspace. Add 1/2" to backspace calculations.

 

Someone want to quote the OE tire/rim info... I can’t recall, but I think it is a +25 offset?