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I'm looking at a set of wheels that have an offset of 48. Is that ok?

16x7 offset 48 w/ 205/50/R16 rubber.

Roo

 
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Looking in the wheel and tire FAQ I found the offset calc spreadsheet.

I punched in what the FAQ claims is the 'stock' offset (45 on a 6" rim)

Info about the Existing Rim
Offset (in mm) 45
Width (in Inches) 6
Width Outside Mounting Surface 31.2
Width Inside Mounting Surface 121.2

Info about the New Rim
Offset (in mm) 48
Width (in Inches) 7
Width Outside Mounting Surface 40.9
Width Inside Mounting Surface 136.9

Inches Millimeters
Difference in Width 1 25.4
Offset Difference 0.118110236 3


The outer edge of your new wheel will be 9.7 mm further out than the existing wheel 0.381889764 Inches
The inside edge of your new wheel will be 15.7 mm further in than the existing wheel 0.618110236 Inches


Still concerned...
Roo

 
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I'm gonna move this to the wheels/tires section...

 
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Yeah, I should have put it here originally. This is a hypothetical question -- I'm mostly hoping to understand what offsets are valid.

There is plenty of information about how to calculate the offset (see the FAQ). But once you've got the number that says "ok, your new tire will be different than the old one" -> you don't know if that's too far or not.

An extreme example would be say: I'm using an offset of 24mm on a 17x7 wheel. The offset calculation can be done by the spreadsheet, but nowhere does anyone provide data on how big the civic wheel well is. Of course it will also matter if you're dropped too.

What we need is a 'super offset/drop/tiresize" calculator. If someone can figure out the formula, I'll hack up a java-script webpage to do it.

Roo

 
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Too much offset. Its gonna rub.
Offset should be between 35 and 45 at the extremes, but more like 38-43

 
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Thanks, I can accept that answer as a "rule of thumb".

But the difference between 45 and 48 is 3mm -- heck, the popular 40mm offset is only 8mm difference. That's not even 1/3 of an inch. Hard to believe that its going to "rub" for certain.

I'm sure there are people here with 7.5inch wide rims and a 40mm offset. So let's do the math.

Info about the Existing Rim
Offset (in mm) 45
Width (in Inches) 6
Width Outside Mounting Surface 31.2
Width Inside Mounting Surface 121.2

Info about the New Rim
Offset (in mm) 40
Width (in Inches) 7.5
Width Outside Mounting Surface 55.25
Width Inside Mounting Surface 135.25

Inches Millimeters
Difference in Width 1 25.4
Offset Difference -0.196850394 -5


The outer edge of your new wheel will be 24.05 mm further out than the existing wheel 0.946850394 Inches
The inside edge of your new wheel will be 14.05 mm further in than the existing wheel 0.553149606 Inches


So a 7.5" wide rim with an offset of 40mm has is barely more than 1mm difference from the 48mm offste 7" wide rim. Why would one rub and not the other?

I'm not saying your advice is bad, its a good rule of thumb. I just can't make it make sense on paper.

Roo

 
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Lower the car, set your camber and then account for the fact that the rear suspension moves in an arc. The gas filler neck is in the way of the left rear tire. Put all that together, load your suspension and feel around for clearances. The other difference is the profile of the spokes You have calipers that you have to clear, the more offset built into the wheel, the less is built into the hub. So its not just rubbing the car, you can also rub the calipers. Since every rim has a different spoke depth, its hard to say what fits and what doesn't. So to be safe... people have come up with these limits of what works for sure, and what has less than 100% liklihood of fitting on.

 
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I appreciate the detailed follow-up. Can I request that the "rule of thumb" of 35mm to 45mm offset information be put into the FAQ?

Possibly with a few common examples of wheels/tires that do work. IE: if you want to be super safe, get this tire/rim combo in 17. In 18's do this.. etc..

Roo

 
Rep Power: 265

So if you were gettin' 18X7.5" would you go with the 35 offset or 45 offset? Since they're both extremes?