'j' Markings On Wheels, How Accurate Are They?

[johnnyboy666 195 1 Cars]

Something that I've always assumed up untill recently is that a wheels 'J' measurement was the width in inches.

 

Whether that is measured from the inside of the rim lip or the outside seems to make little difference to the fact that most rims I've measured differ to what they are supposed to be.

 

Any reason for this or am I just incapable of using measuring implements correctly?

 

This sort of thing could cause issues when judging whether wheels will fit an application or not

[MiniGibbo 142]

Ive never understood it, ive measured some 8.5j wheels in the past and they where nowhere near 8'5"s...?

[Slo 283 1 Cars]

http://www.driverstechnology.co.uk/wheel-offset.htm Edited May 24, 2012 by Slo

[welshpug 1,623]

J is the bead type, wheels are measured bead to bead.

[johnnyboy666 195 1 Cars]

Yeah I think my wording was a little off, I realise that J refers to the bead, but youd expect for example a 7J rim to measure 7" from bead to bead, but it seem this isnt always the case

[welshpug 1,623]

they probably just use the closest complete marking, i.e 6.5" 7" etc, though I've never measured any, what have you measured and found to be different from stamped markings?