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I've got a non-standard set of rims and I'd like to know what Offset they are as I believe they are incorrect for the car they are on.

I have a rough idea what Offset means but how do I easily and accurately measure the Rim Offset?
Can it be done while the wheels are on the car or do I have to remove one?
Can it be done without removing the tyre from the rim?
Is it likely that the offset is stamped somewhere on the rim (I can't see it, but maybe I should look harder)?

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    we've been having a lot of discussions about effective questions - I think it would be helpful to add the vehicle and the specific wheels that you are using.
    – Bob Cross ♦
    Jun 3, 2011 at 14:36
  • Actually Bob, I was going for quite the opposite. I believe the subject matter is simple enough so I wanted the question (and subsequent answers) to be general enough to apply to any set of rims. Why have questions about measuring the offset of every different set of rims out there when the answer is going to be (pretty much) the same for all of them. The idea being that if you have a generalised question with a solid generalised answer it can be used to point people with more specific questions to for years to come, this is where the Stack Exchange software and community model really shines.
    – Scott
    Jun 6, 2011 at 2:03
  • (I ran out of comment space) With that said, if you still want me to change the questions let me know and I will.
    – Scott
    Jun 6, 2011 at 2:03
  • hey, it's your question - you should do what you think best. Maybe it's worth having another question for your specific situation. Just thinking about google targets: then you would show up for "how do you measure offset?" and "what is the offset for vehicle X?"
    – Bob Cross ♦
    Jun 6, 2011 at 13:14
  • The offset (and diameter and width) should be stamped on the rim. If not, measure as Bob said.
    – Atto
    Jan 17, 2020 at 9:20

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To measure offset, you really need to know two numbers (illustrated here):

  1. The inner to outer edge distance: this is effectively the track width of the wheel if you were to drive around without a tire mounted.
  2. The inner edge to the hub or outer edge to the hub: either will give you the basic number, though you'll need to apply the appropriate minus sign to in the equation.

The offset is then the difference between the half the number you found in step one and the number that you found in step 2. I.e., the distance of the hub from the true middle of the wheel.

It is possible to measure the offset either with or without the tire mounted, though measuring unmounted is far more convenient. I would recommend that you contact the vendor and see if they'll just provide you with the offset, though. That isn't trade secret information and Tire Rack, for instance, has specific guidance on which offset is appropriate to which vehicles.

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