Why so small, tire?

May 10, 2007 4:47 PM

Help me understand what's wrong with my new bicycle tire.

I'm trying to put a new front tire on my bicycle. Basically the instructions seem to be: remove the old tire with clips, put air into the tube (a little bit) until it takes shape, put the tube in the new tire, put the new tire on the bike.

I bought a 700x23 tire to replace the current tire, which is 700x26. My understanding is that the 700 refers to the size of the tire, and the 23/26 to the width. So I thought I was all set. When I go to put the tire on the bike, though, it doesn't seem to want to fit all the way around the rim. Also, when I put the tube into the tire it doesn't expand smoothly throughout... it seems to develop some kinks, like the tire is too small.

I put the other tire back on the bike, which was 100x easier. Is there some reason why this tire won't fit on the rim, or do I just need to try a little harder?

posted by selfnoise to sports, hobbies, & recreation (10 comments total)

I'm far from an expert, but my understanding is that different manufacturers fudge the numbers here and there, so a 700 by one manufacturer may not be sized identically to someone else's 700. Are they different manufacturers?
posted by davejay at 5:01 PM on May 10, 2007

Tire diameter sizes and rim diameter sizes vary across manufacturers and across product lines. Especially since making a tire smaller makes it lighter, and weight is a big issue.

I wouldn't use a tire that was too hard to put back onto the rim with your hands - you'll have to deal with the same problem once you get a flat on the road, with less time and less patience.

If the new tire has kevlar beads, the folds in the tire may be causing it to appear to have a smaller diameter. In that case, seat the tire correctly and inflate the tube to normal pressure, then deflate and try again. This should put enough pressure on the tire to remove any lingering tightness.

For the tube - make sure it can be used for 23C. Some tubes are designed for 25C-31C or similar. Tubes are cheap.
posted by meowzilla at 5:16 PM on May 10, 2007

Some beads are just a bitch to get on the rim. Kevlar beads are the worst. Just takes some time, patience and muscle. I try not to use levers to get the tire on but sometimes there's no other option.
posted by DieHipsterDie at 5:18 PM on May 10, 2007

Some tires just have a really tight bead, and you will have to pull hard to get it on the rim. It's also not unusual - though it is a bit disconcerting - for the tube to seem to "want" to be a larger diameter. As long as you don't get it pinched in between the tire and the outer wall of the rim, though, it'll be fine.

Get one edge of the tire seated on the rim - that should be easy. Get the tube stuffed in the tire with a little bit of air in it.
Then pull for all you're worth to get the other edge of the tire seated. It'll probably be easy until the last lousy inch or so.

700 is 700. Unless you bought a mountain bike tire, which you clearly didn't, it'll go on there.
posted by Wolfdog at 5:18 PM on May 10, 2007

Okay guys, thanks. I was concerned about using too much oomph, but I will try a little more.

The new tire is a different manufacturer, and it is indeed kevlar.
posted by selfnoise at 5:22 PM on May 10, 2007

See this previous thread.
posted by scalespace at 6:04 PM on May 10, 2007

Ok, I used the strength given to me by mysterious gamma rays and got it on. Wolfdog's suggestion to start with one corner in and go around the other edge was actually what was on the tire's price sticker, just in exceedingly cryptic form. And it worked... after a while. Tube seems to have inflated happily, too.

Thanks everyone! (and scales for that link... I'd missed that one.
posted by selfnoise at 6:22 PM on May 10, 2007

Tubes have ranges. You may have a 19-23mm, say, and your 26mm could be too wide. It's unlikely, but it will fit differently. 23s and 26s will generally take the same tube.. I'd figure 90% of road tubes sold would cover both. There are some ultra-narrow ones for racing that save weight, and some wider ones for cyclocross and other 30+ width tires.
posted by kcm at 6:26 PM on May 10, 2007

I am glad you got it on. Wolfdog had it right. One more thing if you have trouble in the future, pams are stonger than thumbs. Sometimes it is really, really difficult to get that last bit over the rim, you just got the tire that was the smallest of the lot perhaps. Instead of using your thumbs, grab the whole rim and use your palms to push it over the rim. You are just getting more muscles into the mix.
posted by caddis at 7:58 PM on May 10, 2007

+1 wolfdog. A 700 is a 700, but what with manufacturing tolerances and whatnot, there will be tiny discrepancies. I've found Continental tires to always be notoriously tight.

There is a kind of tool you can buy to get that last few inches seated on the rim: it's called a "tire jack" and I'm not ashamed to use one. I've also found, happily, that even really tight tires tend to loosen up a little once they've been in use for a while, so it's not quite impossible to change tubes on the road.
posted by adamrice at 7:15 AM on May 11, 2007