SaharaMike

OK,
I am familiar with wheel offset from the standpoint of I know it is where the wheel connects to the hub (spindle, etc) in relation to the midline of the rim.

So my Sahara has a particular offset which is "X". Obviously with a stock tire -255/18/70- I am not rubbing at all. Yet, from what I have read, when I go to a 315/17/70 I will need a spacer (1" to 1.5") to offset my wider tire. Why couldn't I just get a rim with a 1" greater offset? If my current offset is "X", why couldn't I buy a rim that was "X" +1"? It doesn't appear that anyone is doing that, rather they are going with the spacers. (note to add I do realize my stock rim is 18" and my new rim will most likely be a 17")

Also, if my current tire is approximately 32", and I want to go to a 35", are there tire choices that have the same width but a taller sidewall? I am not looking for a tire that sticks out. I would rather have tires that either remain under the fenders or stick out only minimally.

I'm just really hesitant about spacers in general. I am not planning on doing any hard core rock climbing.

Thanks for the help everyone.

Mike

armycop

If you want to add a new wheel and wider tire, you just have to look for a wheel with less backspacing than the factory rims. The standard backspacing is around 6 inches and many aftermarket wheels have rims with less backspacing which would not need spacers to fit larger tires. If you go with 4.5 to 5 inches of backspacing, that will have the same effect as a 1.5 inch spacer. (Pushing the wheels out more). As for adding a 35" tire, the problem is height and rubbing the fenders while steering. If you buy a budget boost lift, that will help with the clearance for height. The 35s will fit stock, but if you hit some bumps, you run the risk of damaging your fenders.

SaharaMike

Does anyone know what the stock offset is for a Sahara 18" wheel? That way I can start looking>?
Thanks

BLKRUBI

6.25" . You have to use a spacer to use the stock wheels with larger tires. If you want aftermarket wheels, you should get them with less backspacing which eliminates the need for a spacer. People are doing one or the other. I haven't seen people using aftermarket wheels w/ spacers but I'm sure some have. Too me, that kind of defeats the purpose of getting the aftermarket wheels unless you can't get the wheel you want with the backspacing you need.

gjeepguy

actually 6.25 is the backspacing. the mounting surface is 6.25" from the back of the 7.5" wide rim.

the offset is +2.5". or 2.5 inches from the center of the rim (3.75)

gjeepguy

From AEV website:

Offset
What the book says: Offset is a measurement from the mounting surface of the wheel to the centerline of the wheel. This measurement is typically expressed in millimeters and can be positive or negative. In the case of all newer factory Jeep wheels, they are all a “positive offset,” meaning that the mounting face of the wheel is outboard of the centerline.

What the engineer says: “Many aftermarket wheels come with a generic offset that is designed to “fit” as many vehicles as possible so that dealers only need to carry one wheel…the issue here is that the wheel doesn’t really “fit” any application…this is why you see Jeeps with the tires sticking out three inches past the flare. This may be OK in sunny southern California, but guys who live where it snows can be in for all sorts of white knuckle handling not to mention a huge mess on the side of the car. With the proper offset, even 35” tires can stay neatly tucked under the Jeep, it’s a common misconception that you need to have them stick out to clear.”

Backspacing
What the book says: Backspacing is the measurement from the wheel mounting surface to the outside rear lip of the wheel. Backspacing is not used in the wheel industry because it really doesn’t mean much unless you know the width of the wheel and what kind of construction was used to make the wheel. Backspacing can be helpful if you are comparing the exact same width and type of wheel.

What the engineer says: For instance, your friend might tell you to get a wheel with 4” of backspacing to make your Jeep work really well. If you purchase a 16x7, the outside edge of the wheel will be 3” outboard of the wheel mounting surface, however if you purchase a 16x10 also with 4” of backspacing, you’re outside edge will be six(!) inches outboard of your wheel mounting surface. So while your friends Jeep might look great with the 16x7 with 4” of backspacing, your Jeep might end up with the tires sticking out three more inches on either side, a totally different look. The other factor in backspacing vs. offset is how the wheel is made. Wheel width is measured between the bead seat surfaces on the inside of the wheel. Backspacing is measured to the outside of the wheel, so if you have a thick bead like many aluminum wheel do, or a different type of wheel weight seat, you may not end up with what you want.

BLKRUBI

Sorry, that's what I meant 6.25" backspacing.......and offset is usually in millimeters, not inches.


Here's a cheat sheet on wheel size/offset/backspacing.....

https://rsracing.com/tech-wheel.html


........plus other useful info.

gjeepguy

thats what i said... i was just comparing the 6.25 backspacing and the +2.5 inches offset.

SaharaMike

So if I want to run 17" or 18" wheels, should my offset be 1.5+ rather than the stock 2.5? That would bring the mounting surface closer to the center hence, preventing the necessity of a spacer.

gjeepguy

yes but, it really depends on what width rim...

7.5" stock rim width - 6.25" backspacing (or +2.5" offset) = face of rim is 1.25" past mounting surface.

8" rim - 4.25 backspacing (or +0.25 offset) = face of rim is 3.75" past mounting surface.

10" rim - 4.25 backspacing (or -0.75 offset) = face of rim is 5.75" past mounting surface