's Forum Archives - Cyclo-Cross

Archive Home >> Cyclo-Cross(1 2 3 )

Couple Stupid questions about cross and MTB tires(4 posts)

Couple Stupid questions about cross and MTB tiresbobobo
Oct 31, 2002 12:19 PM
1) can a size 26" tire be mounted on a 700C rim or vice versa?
2) what's it mean when it says its a size 26",1.5 tire versus say 26",1.0 tire?
3)What exactly is a tubeless tire and what is their typical PSI running pressure and purpose?

Thanks much
OK, I'm going to assume you're serious ...GlowBoy
Oct 31, 2002 1:06 PM
Here's my stab at answering your questions:

1) No. A modern 26" tire mounts on a 559mm rim and a 700c tire mounts on a 622mm rim. The new 29" mountain bike tires ALSO mount on a 622mm rim. The designations 26", 29" and 700c refer to the approximate diameter - 26", 29" and 700mm, respectively - of a "typical" tire mounted on that rim, but they are very approximate.

2) The second number is the width. A 26x1.5" tire is 1.5" wide and a 26x1.0" tire is 1.0" wide. Approximately. A 700x25c tire is 25mm wide, and a 700x32c tire is 32mm wide. Approximately. Tire widths can vary considerably from their designation, depending on the rim used, the tire pressure, the manufacturer of the tire, and whether they've decided to measure the casing width or the total width including tread.

3) There are several different tubeless systems out there and they are pretty much in their infancy. Usually it involves a special tire, a sealed rim and some kind of sealant. To my knowledge it is only available for 26" tires at this point - I don't know of anyone offering it for 700c or 29", though that is likely in the future. The advantage of the system is that you can run MUCH lower tire pressure without risking pinch flats, which improves both traction and ride quality. The drawbacks of these systems, so far as I've heard, are that they lose pressure quickly (going flat within a couple of days, and may even require topping off during a ride), and that if you puncture or cut the casing on your tire during a ride you are dead in the water - unless you carry a spare tire, of course, but that's a whole lot heavier than a spare tube.

Here are a couple of great links for information about tire sizing and tires generally:

Probably more than you ever wanted to know. Hope this helps.

- Dan
thanks glowboy, great info, nmbobobo
Oct 31, 2002 1:58 PM
Doesn't he mean tubs, rather than tubelss though? nmEager Beagle
Nov 6, 2002 6:03 AM