Tires: Offset, Rim Dimensions

Question
Hello.

I have 16" wheels, 5x100mm, with 45mm offset.

I'm might buy some second hand wheels but wanted to be sure I'm getting the right size.  Is it the 5x100mm what I mostly need to be concerned about.  Or do I need to be sure on the offset as well?

Also, I've heard of these being sized as 5x6.5 JJ.  What does the 6.5 and JJ refer to?

Thanks.

Answer
Ray,

This is not a job for amatuers.

Not only is the bolt circle:

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=92

But there is also offset:

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101¤tpage=91

and centerbore:

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=91¤tpage=92

But those dimensions don't complete the picture.  The brake components have to have clearance and there is no dimension that specifies that!!  That is specific to the wheel so you neeed to know the manufacturer of the wheel and the part number!

Here's a more in depth look at this area:

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=95¤tpage=90


And your last question:  

"Also, I've heard of these being sized as 5x6.5 JJ.  What does the 6.5 and JJ refer to?"

I think you mean 15 X 6.5:

- 15 is the nominal diameter of the rim in inches.  This matches up with the tire size.

- 6.5 is the width of the rim

- JJ is the rim flange contour - and for practical purposes you can ignore that.