wheel size with offset...how does it work?

[shift00]

OK, im retarded guys from everything ive read on here i still cant figure out how this works. ok, this is my situation i want to run 235/60/r15 on a 8.5inch rims with an 4.5 offset in the back and 215/60/r15 on a 6inch rims on the front with the same offset. the problem i have is when i put on a 2inch wheel adapter(or whatever size it maybe) converting it to a 5lug how do i play with my offset. Now i will be have a set of tokico hps front and rear so i don't know if that will make a difference at all. Im going for the muscle. the street/ autocross racing.

 

man your guys comment back have been alot of help...sorry if i ask stupid Q's sometimes i just don't want to make a mistake. thank you joe

[blueovalz]

...i want to run 235/60/r15 on a 8.5inch rims with an 4.5 offset in the back and 215/60/r15 on a 6inch rims on the front with the same offset.

 

 

There is a plethora of examples, drawings, and text on the internet discussing this.

 

Some of the issue may be your understanding of the terminology. You're quoted 4.5" offset is what I believe to be a term called BACKSPACING, not offset.

Any spacer creates a smaller combined backspacing, and subtracts algebraically from the offset value. The front rim in your example has a 4.5" backspacing with a positive 1/4" (~6mm) offset. Adding a 2" spacer will reduce the combined (wheel lip from the hub surface) backspacing to 2.5", and subtract from the offset by 2" (+ .25" - 2.00" = -1.75" offset, again for the combination of spacer and wheel).

 

I may have confused you even more than you already were. If I were you, I'd focus on your backspacing needs first, then figure out if you've got an appropriate amount of offset.

[OlderThanMe]

I'd try to get maximum backspacing first and then figure out how wide of a tire you want to run and size the rim from there.

4" is safe on stock struts, 4.5" is close(more narrow tires)

5" is safe on coilovers and 5.5" is close.

For the most part on 70-early 74 models...

 

BTW it isn't likely that your 235/60r15 rear tires will clear the stock fenders. Why the narrow front wheels? Drag racing? You are probably going to want wider tires for the front or I see a lot of understeer in the car's future...

 

Good luck!

[shift00]

Ok thats pretty easy to understand...So what do you guys think about my tire setup on this? i was reading a couple stickies and some people think that ia a good tire setup others dont!? OLDERTHANME, you were saying that i will understeering issue...front a smaller front tire? My thought on it was i simply didn't need a 235/60r15 in the front or a 215/60/r15 in the rear, so i mixed it up and im guessing thats not such a good idea?

[Brad-ManQ45]

I have an '83 ZXT and am running 0 offset rims and 235's on the rear and 215's on the front with no issues.

[BurnoutZ]

So in the end what is the difference between a higher offset and a lower offset for a rim? Is one more appealing? Does one perform better? I am looking at 17 x 9.5 rims for the front and back. They offer them in low offset and a higher offset.

[hughdogz]

So in the end what is the difference between a higher offset and a lower offset for a rim? Is one more appealing? Does one perform better? I am looking at 17 x 9.5 rims for the front and back. They offer them in low offset and a higher offset.

 

Offset is the distance from the centerline of the rim to the mounting surface. If the mounting surface was exactly at the rim centerline, then it would be zero offset. If the mounting surface is outward of of the centerline, it is positive offset. Negative offset is inward.

 

To quote from JohnCoffey, offset doesn't matter, offset doesn't matter, offset doesn't matter. It is overall width and backspacing you're concerned about. Offset only plays a role in how deep the "dish" is. Positive offset is less appealing to me than negative or zero in this regard, since there will be less dish.

 

Say that you have a 7 in rim with zero backspace. This gives you 7" width (inside to inside where the tire beads mount) + 1" for the thicknesses of tire mounting flange. The zero offset would put the backspace at 4 inches. Now, with an 8" rim +1" would give you 4.5" backspacing at zero offset. You can see that offset doesn't tell the whole picture.

 

If you have too much positive offset (in reality too much backspace) the inside of the rim will hit the strut tube (or the tire will hit the spring perch) when you mount the wheel. You can put the rim further out using a spacer to decrease the backspace.