I'm confused about wheel backspacing and offset. What would make my wheels stick out more: one's with 4.5" backspacing or one's with 3" backspacing??? Same with offset, what is that? I want my wheel base wider than it is by a few inches.

 

Backspacing & offset are related - CLICK HERE for several sites explaining the relationship.

This is the best pictorial explanation I have ever found:


3" backspacing will stick out further than 4.5" backspacing.

 

^^^

4.5" of backspacing on a 15x7 wheel is perfect imo. It flirts with the wheel wells but is an aggressive stance. I think 3" is too much. Your whole wheel will practically stick out of the wheel well up front.

The short answer: The lower the backspacing, the more the wheel sticks out. But this all depends on how wide the wheel is too.

The definitions:

Backspacing is the distance from the hub mounting surface to the inside lip of the wheel (measured in inches).

Offset is the distance from its hub mounting surface to the centerline of the wheel. And then you get into the 3 types of offset after that. Goes into a lot of detail. But the 3 types are zero, positive, and negative offset.

 

It's worth noting that wheel width should be considered together with backspacing.

4.5" BS on a 7" wheel will be different than 4.5" BS on an 8" or 10" wheel.

Offset combines wheel width and backspacing so that you only need to compare the one number which, in my opinion, makes it easier. However, backspacing seems to be a more tangible concept that people have an easier time understanding.

If you follow swartlkk's link and then click the image search, there are a number of simple charts that combine wheel width, backspacing and offset which often makes it easier to understand how they work together.

 

Matt, I think what you meant to say is that offset will change for a fixed back spacing & variable rim width since it references a center plan between tire beads that changes location in relation to the back of the rim as the rim width changes. If you are holding BS fixed, offset must change as rim width changes. If you hold offset fixed, BS must change as rim width changes.

Lets say that the back of the rim is 0.25" away from the inside tire bead. With 4.5" BS and a 7" wide rim, the offset is +1.25". Stretch that to a 10" wide rim and the offset now becomes -0.75".

If you hold offset fixed, then backspacing would change. So for an offset of 0.00", a 7" wide rim with the same 0.25" lip would have 3.75" BS while the 10" wide rim has 5.25" BS.

 

Yeah, I forgot to put I was basing my backspacing number off of a 15x7 wheel. On a 15x7 wheel, I think 4.5" of backspacing is perfect. My bad on that one. But yeah, the wheel width matters a good bit. I know those 17x9 'Maro wheels (Of course, they had 5.25 or 5.5" of backspacing) that I tried to put on my blaze wouldn't work worth a darn. They rubbed frame along with half the front end lol.