Originally Posted by
noglider
As von Neumann said, in theory, there's no difference between theory and practice, but in practice, there is.
Those of us who have more experience than you, and we do exist, know that the tire's width does not match the rating. There are many reasons for this. One of them is that the width rating is not a measurement of inflated width but of bead-to-bead distance, divided by 2.5. Reading the specifications and telling us that this is what we encounter is not a substitute for knowledge gained empirically. Stating that you are the expert does not make it so. Enough of us know about the variations between rating and measured width that asking about experience makes sense to many of us, though you lack enough experience to understand the usefulness of the question. So listen and learn rather than call the rest of us wrong. OK? Try it.
Sorry man. I like you,and have a modicum of respect for you, but your wrong.
There's already one example of an HS420 is this thread that is dead on. 39.1mm with a 40 ETRTO width rating (which is tyre width and not bead to bead width.)
My guess is that most users here are not using the ETRTO but this old system with inches or the 700c system, which is also not the same.
Several Schwalbe tyres will be 700x32c but 35-622 and will measure that size exactly. The is very true for tyres over 2 inches in width.
I think most people in this thread are incorrectly using (the needlessly unfortunately complicated) two non-interchangable measurement systems.
Thus, I challenge people to actually post the ETRTO and the actual measurement of the width with a caliper and let me know how it goes.
I will do this on the next day that I ride into work to demonstrate that Schwalbe does keep it within ±1 mm of the ETRTO.