Backspacing question

[BaliLover]

I know backspacing and offset are related, but are also 2 different things completely. Offset is the distance the mounting surface of the wheel is from the center of the wheel, and backspacing is the distance the rear lip of the wheel is from the mounting surface. This got me thinking, shouldn't there be a specific max backspacing, no matter what wheel, for a particular vehicle since no matter what wheel it is, the distance between where it mounts to the hub and where the suspension is will always be the same?

[hannibal]

Offset, backspacing and WIDTH: the three are related.

Only reason there's no magic backspacing (or offset) is because wheel mfg have to consider both the front and back (inside) of the wheel. You gotta know width plus either backspacing or offset to determine how a wheel will fit.

[BaliLover]

There is a MAXIMUM backspacing for each vehicle because the distance from the surface of the hub to the suspension will never change no matter what width wheel you go with. Backspacing is just that, the distance from the mounting surface to the innermost part of the rim. Assuming your tires don't bulge out beyond this point, you could physically measure the distance. Say you're running an 18" wheel. You measure 9" up from the center of your hub, and measure inward from that point and see how far the mounting area is from the suspension. This is your maximum backspacing for ANY 18" wheel no matter how wide. If you exceed that backspacing, you will hit your suspension. However, you can go with less backspacing and end up farther from the suspension.

You can modify fenders, add flares, roll, widebody, etc to correct for wheels that are too far out of the body (too low of an offset/ too little backspacing) but there isn't much you can do aside from running spacers to correct for too much backspacing without modifying your suspension. My post never mentioned total fitment, only the fitment when it comes to your suspension; IE backspacing.

From what I can tell on a 17" wheel, the maximum backspacing (once again, assuming your tire doesn't buldge beyond the rim) is 5.25" and that is pretty damn close to touching my coilovers. Theoretically I could run a 17x20 in the front and as long as it had no more than a 5.25" backspacing, it wouldn't touch the suspension. Mind you, you would't have any turning radius because you'd touch the framerails/inner-fenders, and you'd be sticking out ~15" from the hub, but you'd still clear your coils.

[hannibal]

Youre right. Not sure what was going thru my head.

I guess domestic guys always talking about backspacing instead of offset were on to something.

I would depend on diamater as you said. Coming up with a backspacing/diameter fitment chart sounds like a good project.

you're running an 18" wheel. You measure 9" up from the center of your hub, and measure inward from that point and see how far the mounting area is from the suspension. This is your maximum backspacing for ANY 18" wheel no matter how wide.

You would ahve to add an 1/2 inch to your horizontal measure, but your absolutely right.

BaliLover for Wheels/Tires/Suspension moderator!