bragi

This question is possibly a better fit in the commuting forum, but we all ride bikes for transportation, so I'll ask here:

Earlier today, I replaced my 2009 Continental Contact 622-37 tires with new Continental Contact tires. (It amazes me that I replace rims every 18 months, and tires every 5 years...) I like moderately fat road tires, because they're comfortable in general, and do particularly well on Seattle's vast expanse of crumbling pavement. The new tires are also 622-37 tires, it says so right on the sidewall, yet they are noticeably skinnier than the old ones. What gives? I mean, they're still good-quality tires, but dammit, I thought I was buying 37s, not friggin' 32s or 34's, fer cryin' out loud... Has anyone else noticed this with other brands of tires, or is Continental the only one trying to cut back on materials costs?

prathmann

I've frequently found the stated size to be only a rough approximation. I always figured it was a result of wanting to advertize the lowest weight for a given tire size.

Barrettscv 

Most brands undersize some of their tires. Continental tends to undersize more than others. Schwalbe tends to run true-to-size.

See "Dishonest sizing": https://sheldonbrown.com/tire-sizing.html

Spld cyclist

I found the same thing with a Continental Contact 37 mm. Mine was 34 mm wide when installed on the wheel (I have a dial caliper and can measure this quite accurately). My Schwalbe tires are very close to the stated size. I have a pair of 32 mm Vittoria Randonneur Pro tires that measure 29 mm. Needless to say, it's hard to know what you're getting until they're mounted on a wheel.

GodsBassist

It honestly never would have even occurred to me that 23 doesn't mean 23. I mean these aren't women's dress sizes, the millimeter is standard across the board right? That being said, I've never measured it, I just have a feeling for about how big a 23 is and how big a 35 is… roughly.

I feel foolish now.

Does the width of the rim matter? It would have to, right? I mean if I put 32s one each on a narrow rim and a wide rim and both fit, the width of the tire will be different right?

gerv 

I have the same problem ordering shoes online. I always look to the comments to see if anyone says "Better buy a half-size larger."

I have a 32 mm Pasela Tourguard and a 32 mm Schwalbe Marathon in front of me right at the moment. You would never imagine these are the same size.

amdoo

You can't just go by the stated size . . . You need to look at the ETRTO size which is standardized. For example, the SMS stated 32 is an ETRTO 35. In Bragi's case I'm not sure what the deal is because the ETRTO for the Contact II is 37 and if I'm not mistaken when they print the 622x37 it has to reflect the ETRTO rating.

gerv 

Thanks. Good to know... but hard to find. Would you see it on the tire? I'm not seeing it on any of mine.

Wanderer

Usually very close to the bead, and very small.....

bragi

The new Conti tires do in fact have an ISO stamp that says 37-622. However, they are not actually 37s. There's a lot more space between my fenders and tires than there was with the old tires, and I don't need calipers to know that they're obviously thinner. I'm quite willing to believe these tires are actually about 34-622. It's not like anyone is actually checking, except for the end user. In any event, I'm kind of irritated that I didn't get as much tire I as thought I was getting, and am seriously thinking of returning them and getting Schwalbe Marathon instead.