15x8 w/3.75" backspace question

15x8 w/3.75" backspace question

Terrible backspacing for BBP brakes front and rear.

In the front 205/60/15 is as wide as you should go. They'll already stick out further than 225/60/15's on 15x7's with 4.25" of backspace, which were just about maxed out for size on my Duster. They didn't rub but those 205's with 3.75" of backspace will stick out another 1/8" already. They're shorter though so that will help.

In the back the 15x8's with 3.75" of backspace and a 245/60/15 would be a little further out than the 295's are on my Duster. I needed to trim and roll the quarter lip about a 1/2" to make those fit, but I wasn't running SS springs. So, maybe. I also ran a 1/2" spring offset to get the 295's but with 245's and that small backspace that wouldn't be necessary, you'll have a ton of room to the springs.

33IMP said
He told you what the offset is, indirectly, but as usual it has to be calculated, as opposed to BACKSPACE, which is simple, and measurable. Exactly why I don't like that offset bullshit, besides the fact I can't be bothered to figure out which direction is + and which is minus.
15x8, which is really 15x9, with 3.75 backspace is 3/4" offset, or 18 or so mm, and I don't know or care + or-. The b.s. tells me that.
Since I don't know what year barracuda he is talking about.... 64-66 MIGHT fit, with the SMALLEST appropriate tire for the rim width. (Assuming no wheel adapters. If it has wheel pattern adapters,, there is NO way that wheel fits!) A 67-69 should be easier, considering the more open ww opening, IF it doesn't have too much tire on it.
As always, the wheel with the correct b.s. will fit the best (4.5 bs).

Offset is really useful. For example, if you're looking at two different width rims but the offset is the same, you know that the centerline of the wheel is in the same place. So for example if I'm comparing an 18x9 to an 18x9.5 and they're both +35, I know that the centerline of the wheel is in the same place and the 9.5 will add a 1/4" to both the inside and outside. The backspacing will be different, 6.41" vs 6.66".

It's also super easy to calculate, all you have to know is the centerline of the wheel and either the front space or the backspace. The +/- thing is also really easy. 0 offset means the mounting surface is at the centerline. + means the mounting surface is outboard of the centerline, - means the mounting surface is further to the inside. Easy. Both of the rims in question with a 3.75" backspace have a negative offset, -7mm for the 15x7 and -19mm for the 15x8. And that's with the same backspace! So it tells you the mounting surface moved inboard from center by a 1/2", which means the extra 1" of rim width is all to the outside.