Still dont get what the deal with wheel offset is - Ranger-Forums - The Ultimate Ford Ranger Resource


Wheels & Tires Semi-Tech General discussion of wheels and tires for the Ford Ranger.
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  #1  
Old 07-05-2008
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Still dont get what the deal with wheel offset is

So i need new wheels and i know the lug pattern is 5 on 4.5, but i keep seeing all different offsets on these wheels. my ? is what is an appropiate range for the offset to be
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Old 07-05-2008
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You know....i've never gotten what the "offset" is either. It's ususally listed in millemeters. But backspace...i do get. Rule of thumb, smaller the number = more it'll stick out. bigger the number = more it'll suck in.
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Old 07-05-2008
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guys....

offset is the relationship of the center of the wheel to the mount surface

backspacing is the inside lip of the wheel to the mounting surface

if the mounting surface is changed then both the offset and the backspacing are effected.

both are measurements which change in relation to each other.
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Old 07-06-2008
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so how important is it to get the correct offset? can u just get the bs u want and not worry about the offset?
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Old 07-06-2008
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As far as i know as long as you have the proper BS then the offset really shouldnt be that big of a deal. From what I have gathered if you are running a little lift and want a little larger tire with no rub then you need at least 4 inches of back spacing. If you are running even larger/wider tires something closer to 3.25 BS would be better. I was going to run 16x8 Mickey Thompson Classic Locks with 4 inches of BS wrapped in 285/75R16 Super Swamper Irok's. This would have made it stick out a little more then stock and make it to where i would not rub at all.
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Old 07-06-2008
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I would look for a BS around 3.75-4, thats the perfect amount for a 15 inch rim IMO
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Old 07-06-2008
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Quote:
Originally Posted by rededge02 View Post
so how important is it to get the correct offset? can u just get the bs u want and not worry about the offset?
The ideal offset is the factory offset (+12mm). However, when larger/wider tires and/or wider wheels are installed, it is often not possible to run the factory offset.
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Old 07-07-2008
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If i remember correctly and i usually dont. If your wheel has a 3 inch lip, then you have 3 inch backspacing(from lip to hub,ie mounting surface) but if you get bigger tires you need more offset, it determines how far out the tire sticks out from the truck, bigger tires need to stick out more, YOU WANT THE BACK OF THE TIRE TO BE AT THE SAME POSITION AS STOCK FOR INNER CLEARANCE ISSUES.

so if you have a stock tire on the front and a aftermarket tire on the rear the inside sidewall of both tires should be in line with each other but the aftermarket tire will stick out more, the suspsension stuff will never change, but you can always cut or roll a fender.
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Old 07-07-2008
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See if this helps

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Old 07-07-2008
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Zach that pic doesn't work.
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Old 07-07-2008
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Backspacing: The distance from the wheel mounting surface to the back plane of the wheel. Commonly in inches (SAE)
Offset: The distance from the wheel mounting surface to wheel centerline. Commonly in millimetres (Metric)
1"=25.4mm

Backspacing and offset are related to one another. You must know 2 variables in order to find the third, the 3 variables being Width, Offset and Backspacing.


Backspacing
- (Width/2) = Offset
Example: We have an 8" wide rim with 5" of backspacing. Divide 8" by 2 gives us 4". Using the formula, 5" minus 4" equals 1" of positive offset, or 25.4mm of offset.

Offset + (Width/2) = Backspacing
Example: We have a 10" rim with -48mm of offset. Divide 10" by 2 gives us 5" Divide -48mm by 25.4mm/inch gives us -1.89" of offset. Using the formula, -1.89" offset plus 5" equals 3.11" of backspacing.

2(Backspacing - Offset) = Width
Example: We have a rim that has a backspacing of 4", and an offset of 12mm. 12mm divided by 25.4mm/inch gives us roughly 0.5". 4" minus 0.5" equals 3.5". Multiply that by 2 equals 7" The rim is 7" wide.


Backspacing
Backspacing is the distance from the wheel’s rear mounting surface (hub) to the edge of the rim. The best way to measure backspacing is to place a straight edge across the rims and measure to the mounting surface.

Offset

The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel. The offset can be one of three types.

* Zero Offset - The hub mounting surface is even with the centerline of the wheel.
* Negative Offset - The hub mounting surface is toward the front or wheel side of the wheel.
* Positive Offset - The hub mounting surface is toward the outside of the rim. These are generally found on front wheel drive cars and newer rear drive cars.

If the offset of the wheel is not correct for the car, the handling can be adversely affected. When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be split evenly between the inside and outside. For most cars, this won’t work correctly.
Example Formula

offset = backspacing - (overall wheel width/2)
wheel = 156.5
backspacing = 4″
overall width = 7.5″
4″ - (7.5″ / 2) = 0.25″ positive offset

Last edited by got-dirty; 07-07-2008 at 12:47 PM.
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Old 07-07-2008
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Quote:

Backspacing
- (Width/2) = Offset
Example: We have an 8" wide rim with 5" of backspacing. Divide 8" by 2 gives us 4". Using the formula, 5" minus 4" equals 1" of positive offset, or 25.4mm of offset.

Offset + (Width/2) = Backspacing
Example: We have a 10" rim with -48mm of offset. Divide 10" by 2 gives us 5" Divide -48mm by 25.4mm/inch gives us -1.89" of offset. Using the formula, -1.89" offset plus 5" equals 3.11" of backspacing.

2(Backspacing - Offset) = Width
Example: We have a rim that has a backspacing of 4", and an offset of 12mm. 12mm divided by 25.4mm/inch gives us roughly 0.5". 4" minus 0.5" equals 3.5". Multiply that by 2 equals 7" The rim is 7" wide.
Sorry, these are all incorrect because backspace and width are measured to two different places on the wheel.
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