I have a set of Mickey Thompson L60-15" on the back of my car. It has 10.5" of tread with a 5.5" sidewall. 10.5" equates to 266 millimeters and 5.5" is 140mm. So would this tire roughly be a 260/45 15?

Also I was wondering how well these tires would fit onto an 8" wide wheel. The Centerlines on there now are at least 9" and probably 10", I bought the car this way.

thanks

Well, years ago when they changed from the "letter" series tires to the metric style they said a 275/60-15 was the equivalent to the L60 15
If you want to go with a taller tire you can go with a 255 70 15....
if you get on to : tire rack .com you can get the spec's of what ever tire you want to compare to what you have. Hope this helps.

and yes, both L60-15's and 275/60-15's can be run on an 8" wheel

Thanks for the info.

The "275" spec. of a p-metric tire is the section width - the widest part of the tire when mounted.

If you check your L60s you might find a few extra mms. One variable is the mounted wheel width, it is not standardized. For example, your L60s might be 265mm on a 8", 275mm on a 9", & 285mm on a 10" wheel.