Stupid question: 15 inch wheels measure what?

[Ken Mild]

I have a set of Rallyes that measure 15 inches from top to bottom. Problem is, on them, are mounted 14 inch tires. :puzzled:

So, what gives, do I have 14 inch or 15 inch rims??

Do 15 inch rims measure 16 inches in diameter? :puzzled: :confused:

[Keith Seymore]

Yes. You measure where the bead of the tire seats on the rim.

In other words, if you were looking at an unmounted tire laying on the floor, it would be that smallest diameter you can measure.

K

[Ken Mild]

So Keith, does that mean that I cannot accurately measure if there is a tire mounted on the rim? Because the "outside" lip of the rim is what I measured as 15 inches.

As I said, does that mean that the outside lip of a "15 inch" wheel would actually measure 16 inches?

[carbineone]

Its kinda hard to explain but inside the outside lip there is a surface that the tire actually goes against,your rims are more likely 14x6 and they should be stamped as to their size and you can see this stamping with the tire removed,and yes a 15 would measure app. 16 inches overall.

[Ken Mild]

Thanks Bruce. So 14's it is I guess. :ball:
Oh well, at least they are a little cheaper. :Do No:

[Keith Seymore]

So Keith, does that mean that I cannot accurately measure if there is a tire mounted on the rim? Because the "outside" lip of the rim is what I measured as 15 inches.

As I said, does that mean that the outside lip of a "15 inch" wheel would actually measure 16 inches?

It is kinda hard to explain without the two of us standing over a wheel, but you can sort of estimate with your measurements and subtract off the material thickness.

That probably didn't help, but based on your comments I think you are getting it...

Bottom line is if the tires say 14" (and they are not falling off the wheel!) then they are 14" wheels.