Help understanding tube/tire sizing

I have a bike with 650 wheels, and after going through four (!!) tubes this week, I'm buying some new ones. (Changed my first tube... quite a, um, learning curve.)

I don't understand what all the numbers mean when I go to buy new tubes and tires. The box my tubes came in says...

650 x 18 <--> 23, B1
I understand the 650, and know I need to match that. But what about the 18 and 23?

My tires say
26 x 7/8
I assume I need to match those dimensions exactly? I really don't understand either number, though I suspect 26 refers to inches? (And why are we mixing imperial and metric measuring systems? Agh!)

Hrmm... can anyone help me figure this out?

Well yes - that would be 26inches by seven eighths of an inch.

The first number is the diameter of the wheel you are using (and hence the diameter the tyre needs to be) and the second number is nominally referring to the width of the tyre. So at 7/8 of an inch you are looking at about 22mm.

So your 650x23 tube would probably be just fine. FWIW the ones I buy are usually bracketted - 18-22mm or 23mm-25mm rather than just one size.

For the tube, 18 <--> 23, B1 mean what, exactly? And I must buy exactly the tube I'm using now?

And I assume if my current tire reads 26 x 7/8, that's also what I stick with going forward? (All but the frame of my bike were bought used.) Matching measuring systems, I should be looking for 26" x 22 mm, but all I'm finding is 26" x 23mm. I shouldn't use the 23 mm... right?

This seems like it would be so easy, but when I actually start shopping online, I'm offered 1,000 options and start feeling very confused!

The 18-23 would be fine since the 22mm of your tyre (7/8inch) falls in that range.

Not sure what the B1 refers to. The other commonly used thing to differentiate between tubes is the length of the valve stem. It may have something to do with that?

If you have old conventional square-profiled rims you would use a short or medium length. If you have more aero rims you would need a longer stem to reach through the rim and still have enough length sticking out to get a pump on to pump it up.

Oh - and I have just assumed we're talking presta valves! That is the other thing - you need to make sure you have the right type of valve (shraeder or presta) but I don't imagine they would use a B1 to designate that.

The only other thing I can think of is thickness of the rubber. Some companies make lightweight tubes with thinner rubber. Less rotating mass and all that! Probably not a factor here.

As far as I can see it doesn't matter what tube you use as long as it is the right size for your wheel and tyre combination. And 650x 18-23 will do you fine.

Quote:

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Originally Posted by zia

I have a bike with 650 wheels, and after going through four (!!) tubes this week, I'm buying some new ones. (Changed my first tube... quite a, um, learning curve.)

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It sounds like you are buying the right tubes... but 4 in one week? Bad luck... Or maybe you need to inspect the inside of the tire for whatever is puncturing your tubes. Maybe whatever took out your first tube is still stuck in the tire and taking out the new tubes? I am not too keen on rubbing my fingers inside my tire, and possibly pricking or cutting myself on whatever is stuck in the tire, so I use a wad of cotton ball. The fibers will catch on whatever is sticking through the tire and becomes a 'flag'; real easy to see. Also, I lightly coat the new tube with some talc, to prevent friction/sticking of the tube to the tire, when I install it.

As was mentioned already, there are two valve types. There is schrader (like on a car tire, has a center pin that you depress to deflate) and there is presta (thinner than schraeder, has a small nut on the end that you unscrew part way and then the center post can be pushed in; has no spring action like the schrader- air pressure tends to push the pin closed.) The rim is drilled for one or the other. With a screw-on adapter/reducer, you can put a presta valve tube in a schrader drilled rim, but the schrader tube will not fit in a presta valve drilled rim. I use only presta as schrader tends to slow leak from the valve. Higher pressure road stuff tends to be presta.

OK -- I've found tubes that will work. As for the tire: if I currently have a 26 x 7/8 (aka 22.2 mm), would 26 x 23 work? I'm not finding any 26 x 22.

Also, what are "steel" vs "folded" tires?

I do have a presta valve. As for how I went through 4 tubes this week:

1) tube #1 (came with bike; may be original from 2007?): presta valve malfunction while topping off -- couldn't get the pump head to seat deeply enough. Something appeared to be wrong with the stem (the part that screws). It wasn't "as high up" as the other one. So I put on...

2) tube #2: my first changed tire ever. I pinched it with my lever putting the tire back on. Multiple holes. Unpatchable. Won't do that again.

3) tube #3 finally worked and we completed our ride in record time. But, I went to top off my tire this morningand somehow, the entire little stem vanished! So now I am on...

4) tube #4.

I clearly have some more learning to do, but at least I know how to change a tire now! I'd been quietly dreading that for a while... I knew the workshops I'd gone to where they change a tube in 5 seconds made it look deceptively easy!

See Sheldon Brown's discussion of tire sizing

http://www.sheldonbrown.com/tire-sizing.html

Lots of confusion in labeling, so read carefully. Actually, it's the number like 622 or 559 that needs to match your rim exactly, whereas a variety of tire widths will fit a given rim, and a variety of tube widths (and even diameters) will fit a given tire.

Tips on changing tires: (1) Don't use tire levers to install the tire. Use your bare hands if at all possible. (2) Be sure to push the pump head straight on and off over the valve. The valve tips on presta valves are easy to damaged. Using a pump with a hose is less likely to cause damage than a frame pump with no hose.

Quote:

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Originally Posted by zia

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Also, what are "steel" vs "folded" tires?

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That's the bead area- where the tire hooks into the rim lip. A 'wire/steel' bead tire will keep it's round shape off the rim. They tend to be less expensive and heavier. They also tend to be harder to get on and off the rim. 'Folding' or "kevlar' bead tires do indeed fold; they don't keep a round shape off of the rim and can be folded up for storage. They weigh less than their wire counterparts, tend to be easier to get on and off the rim, and they cost more than a wire equivalent.

If you must use a tire lever to get the tire back on the rim, be careful. The tube can be pinched (as you found out) by getting stuck between the tire lever and rim lip. Take a moment to verify the tube is not wedged between the lever and rim before using. And it can't hurt to take a few moments, after mounting the tire, to squeeze the tire inward away from the rim, and look into that space all the way around the rim, to be sure that the tube isn't pinched. I then pump the tire up to a low PSI (around 8 for a mtb tire, and 20 for a road tire), then let the air out, and then pump it up all the way.

It never ceases to amaze me when I am at the LBS and someone drives their bike over to get a flat changed. It took them longer to drive to the store than just changing it themselves. It is a good useful basic skill to have and yes it can cost a few tubes to learn. If the dead tubes have removable valve cores, unscrew them and keep them for emergency replacements so it's not a total loss.

Quote:

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Originally Posted by zia

OK -- I've found tubes that will work. As for the tire: if I currently have a 26 x 7/8 (aka 22.2 mm), would 26 x 23 work? I'm not finding any 26 x 22.

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The 23s will be fine; most rims take a range of tyre widths, within limits, and you can sometimes find those limits on the rim manufacturer's website. You might find they will take something like 20mm width to 25mm width. I have 650s and I'd happily use that sort of range without even checking, but most 650c roadie tyres will be 23mm, or slightly narrower for some tri tyres.

Just check that you're getting 650c tyres (ETRTO size 571mm) for a 650c rim rather than 26in (ETRTO size of 559mm, which is the garden variety mtb size).

And a huge +1 for Sheldon on tyre sizing.