Just wanted to give folks a heads-up on the 700x37c Conti Contact (2011) tires. They measure just over 34mm when mounted on a 24mm (outside) rim. This was after 24 hours at max psi. By contrast, my 700x32 Vittoria Hypers were only 1mm narrower, and actually taller than the Contacts.

I think it would be helpful if we could compile a list of actual widths for the popular commuting tires. Once I replace the batteries in my calipers I'll post some exact measurements.

Good luck!

Tire manufacturers are notorious for bad sizing. Racers want the lightest gear, so tire manufacturers started claiming wider values than actual so they could say they have the lightest tire in its size. It's followed suit with quite a few non-race tires, but for non-racing rubber the problem seems to be batch-to-batch variability due to sloppy manufacturing tolerances. In an article from Velo News over the summer (about UCI changing the 34mm width max in CX racing) it was brought to light that one manufacturer has a tolerance of +/- 2mm. That means one batch of 28mm tires might be 26mm, while the next is 30mm, and they're within spec.

interesting, I just ordered a pair of Kendas and went up to 38's for my SS and was worried they were going to be too wide but when I got them today I was surprised by how narrow they actually are.

Put a caliper to them. My Conti Gatorskin 28s measured between 26.1 and 27. My 28mm Pasela TGs are 27.6 (closest I've ever seen to claimed) but the 32mm version is 30.8mm

Continental is notorious for having narrower than advertised tires. That said, it does depend, to some extent, on the rims. I've got 700x28 Conti GP 4 Seasons on one of my bikes. The front tire, on a Salsa Delgado Cross rim, measures at 28.4. The rear tire, on a Ritchey Silhouette rim, measure 26.3.

Pasela 28, actual is 27. Michelin Dynamic 28, actual is 29. Michelin Dynamic 32, actual is 33. Michelin City 35, actual is 35.

Width depends on the rims, which accounts for much of the variation.

Yes, but if you always use the same rims, you've eliminated that variable. For example, I have a 700x37 Conti that measures 34mm wide, and a 700x32 Vittoria that's 33.5mm. Both were mounted on the same rim, and inflated to their respective max psi. That discrepancy is not due to the rim(s), but the fact that one company's tire is undersized.

...or they made their width claims based in different rim widths. I know I'm splitting hairs here, but if a rim exists on which the Conti 700x37 measures 37mm wide, then arguably it isn't undersized.

That's a stretch of logic.

Like this guy thinking his tires fit.

Is it? Would you say that the Vittorias in MileHighMark's example are oversized?