FastJake

In one of his articles, Sheldon mentions dishonestly in tire sizing. Tire manufacturers would make tires narrower than they were labeled to save weight on the spec sheet and sell more tires.

I acquired a pair of old looking Specialized Turbo LS tires. On the label they clearly say 700x25. On another part of the tire in tiny font the I.S.O. size of 20-622 is printed. The tires measure 21mm wide when mounted on my rims.

Any insight on this? It's not critical to anything, I'm just curious.

JiveTurkey

What are you asking? Your answer is literally spelled out on your tire. (The answer is yes.)

HillRider

This type of intentional mis-labeling is less prevelent now but still occures. I sometimes think current the 700-23 tire size was just a move to truth-in-advertising for what would have been claimed as 700-25 in the past.

FBinNY 

While tires are truer to the published ISO size, I'm not sure that dishonesty is the right word to describe the variation from the non-ISO nominal sizes in the past.

There was a slow process in moving toward narrower tires, and before people got used to the ISO sizing system makers were probably nervous about marking their tires with a new narrower size, lest potential buyers think there might be a fit issue. Decades ago the standard 27" tire was a 1-1/4. Some makers started making narrower versions, but still called them 27x1-1/4 for a long time before anyone was brave enough to start calling them 27x1-1/8. Dealers and consumers who were more familiar with specific tires knew which ran narrow or wide.

In the tubular world, tire width was never even mentioned, you got to know tire by tire how wide each model was.

Also remember that the marketplace has changed. In the past 99% of the tire business was through a specialty retailer who (hopefully) was able to advise and tell you about the products. Very little product in any category had published specs. These days a large percentage of the business is self service, with consumers making decisions on their own, whether in store, or via the internet. Therefore products need to publish specs and be fairly true to those specs, so buyers can know what they're buying.

simonaway427

Measured width is also a ****ion of the air pressure used while measuring, as well as the rim width on which the tire is mounted.

MileHighMark

What puzzles me is when BOTH sizes are wrong. See here.

FastJake

Hey I have a pair of those Ritchey cross tires too! I actually paid money for them, and was disappointed to find out that they only measured 35mm after spending time measuring my frame and making sure I had room for the 40mm tires I wanted. Oh well, they still work..

MileHighMark

I sent them back to the place where I ordered them from. Loved the tread, but wanted something BIG. Thankfully, the Kenda 40mm Happy Medium actually measures 40.5mm (knob/knob).

ThermionicScott 

Not that this excuses Ritchey, but it looks like your rims are only 16mm wide on the inside. It's too bad the tire companies rarely tell you which rims they use when developing and measuring their tires.

tcarl

Interesting original question. Recently I've cleaned out the ancient pile of junk in the basement and found several (still good) tires from the era mentioned, including some Specialized Turbos. These tires are marked as 700x25, but when I mount them on a rim and air them up, they are the same size as today's 700x23.

Looigi

As an additional data point, I run 23mm Pro3s on HED 23mm wide rims and the tires measure 25.3 mm inflated to ~100 psi.

On a number of occasions I've ridden behind guys with what looked like very narrow tires and asked what size they were. They always said 23mm, but the sure looked way less than that.

Kimmo 

Contis always seemed pretty close to spec, IME.

MileHighMark

Yes, it would be nice to know which rims they base their measurements on. Thankfully, the Kenda Happy Mediums do measure true, width-wise.