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  1. #1
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    23mm tube in a 25mm tire? And presta values

    My Presta valve stem snapped off last night and so I had to replace the tube. When I pulled out the spare I realized it was a 23mm, and the tire is 25mm. I put it in anyway and got it up to the right pressure (115 lbs - I'm a big dude).

    What's the impact - if any - on using a smaller tube in a larger tire? Is there any reason to think the tube is going to have a shorter life expectancy? Should I swap it out for a 25mm tube right away, or just leave it alone?

    And about those Presta values - other than being more Euro and "pro" looking, do they have any function advantage over a Schraeder valve? I've always found them more finicky to use and they feel more delicate. I've worried about them breaking, and then it happened last night.

  2. #2
    tlg
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    No problem at all. Tubes are rubber and stretch. We're talking about 1mm(.04"). Pump up your tube sometime outside of the tire. Watch how big it gets. Then ask yourself... is .04" really an issue?

    Presta valves are better because they allow for a smaller hole in the rim. With narrow road rims, putting on a large schraeder hole, weakens them.
    Be more gentle. You don't have to force the pump on. I've never had a presta valve break... in thousands of uses.
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  3. #3
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    I've seen how big tubes get outside a tire, so that's why I put it in and went riding. I wanted to check there wasn't a reason to swap it out. Thanks.

    I always have some trouble getting the chuck of my floor pump on presta valves. I takes some effort, and getting it ALL the way seated, to get air flowing into the tube. Maybe it's my pump?

  4. #4
    tlg
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    Quote Originally Posted by B_arrington View Post
    Maybe it's my pump?
    Maybe. Some go on better than others.
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  5. #5
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    Presta valves have a functional advantage much more important than the smaller hole in the rim. Unlike Schrader valves, they are kept closed by air pressure alone (when the nut has been loosened) rather than by a spring. To put air in a through a Schrader valve, you have to depress the spring-loaded stem with a pin, and hold it open while you pump air in. When you release the pump head, the pin is still holding the valve open, and some air usually escapes from the tube before the spring closes it again.

    The amount of air lost may seem small, but it's difficult to control, and with a low-volume high-pressure tire as on road bikes, it can be significant.

    With Presta, differential air pressure operates the valve. To put air in, the pump creates higher pressure than what's in the tube, the valve opens, and air goes in. As soon as the pump stops, the outside pressure drops, and the valve closes. When you remove the pump head, you lose no air from the tire ( if you hear air escaping, it's coming from the pump reservoir).

    So Presta valves are much better for bike tires. Learn to use them right and you won't have any problems. The delicatge valve stem just requires a little care in removing the pump head straight.
    Have you ever been to Electric Ladyland?

  6. #6
    wim
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    It takes some effort, and getting it ALL the way seated, to get air flowing into the tube.
    You don't need to seat the chuck all the way to get air flowing. Seat it just enough for it to not come off during the pumping. That way, you don't have to wrestle it off—which is the number one cause for breaking valves. Before attaching the chuck, are you tapping the valve core up into the valve once or twice to unstick it?

    Two suggestions, but only in case you continue to have problems: Get a pump with a screw-on chuck (Lezyne makes one like that, perhaps others) or push your slide-on chuck on so lightly that it just barely seals. Gently holding it onto the valve with one hand, pump forcefully with the other hand. Great exercise to develop arm muscles on one arm. :-)

    I never broke a Presta valve in almost 50 years of pumping, so as said by others, it's possible to do no damage ever.
    Last edited by wim; 08-16-2013 at 07:03 AM.

  7. #7
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    Most tubes I buy are labeled as 700 x 18/25 so would be good in any tire from 18mm to 25mm.

  8. #8
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    Thanks for the usage tips.

    JCavilia - that is an excellent explanation of the practical difference between the valve types. Thank you.

  9. #9
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    So I found out that its really not a good idea to run an 18-23 mm tube in a 25 mm tube. Turns out the part of the tube where the value is doesn't inflate like the rest of the tube. It creates a lot of stress and eventually cracks the tube. The tube only lasted about 5 weeks and 150 miles.

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    Re: 23mm tube in a 25mm tire? And presta values

    Only time I broke a presta was when the bike fell over while I was pumping it with a frame pump. I was left with half a presta in the pump head and a sad walk.

  11. #11
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    Quote Originally Posted by B_arrington View Post
    So I found out that its really not a good idea to run an 18-23 mm tube in a 25 mm tube. Turns out the part of the tube where the value is doesn't inflate like the rest of the tube. It creates a lot of stress and eventually cracks the tube. The tube only lasted about 5 weeks and 150 miles.
    Yah, no. That wasnt the problem. Something else is going on.

    I have had a 18/23 tube in a 29x2.2 mountain tire for quite a while. I carry a road tube on the mountain bike because it is easier tp pack. I am too lazy to change it and its never been a problem.

  12. #12
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    Quote Originally Posted by B_arrington View Post
    So I found out that its really not a good idea to run an 18-23 mm tube in a 25 mm tube. Turns out the part of the tube where the value is doesn't inflate like the rest of the tube. It creates a lot of stress and eventually cracks the tube. The tube only lasted about 5 weeks and 150 miles.
    I am not buying that bit of information, it sounds like you got it from someone in a bike shop.
    And don't forget the one about not hanging your bike from a hook in the ceiling.

  13. #13
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    Quote Originally Posted by B_arrington View Post
    So I found out that its really not a good idea to run an 18-23 mm tube in a 25 mm tube. Turns out the part of the tube where the value is doesn't inflate like the rest of the tube. It creates a lot of stress and eventually cracks the tube. The tube only lasted about 5 weeks and 150 miles.
    Have to agree with everyone else: it is NOT the size difference between tube and tire that caused your problem. Absolutely not. And unless a tube is VERY old or exposed to a lot of ozone or UV light, it will not "crack."

  14. #14
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    You received false information. Just like one of the other posters, I ride with a road tube when I go mountain biking too. Tubes stretch like crazy, honestly, the tube size was not the issue for your flat.

  15. #15
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    Quote Originally Posted by SBard1985 View Post
    You received false information. Just like one of the other posters, I ride with a road tube when I go mountain biking too. Tubes stretch like crazy, honestly, the tube size was not the issue for your flat.
    And you replied to the wrong post. Click on "reply with quote" to the post you want to respond to. You responded to the guy who broke his valve because the bike fell over while he was pumping.

  16. #16
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    Quote Originally Posted by B_arrington View Post
    So I found out that its really not a good idea to run an 18-23 mm tube in a 25 mm tube. Turns out the part of the tube where the value is doesn't inflate like the rest of the tube. It creates a lot of stress and eventually cracks the tube. The tube only lasted about 5 weeks and 150 miles.

    Nonsense.
    "It ain't a teacup that the Queen gave you - it's a bike. Ride it!"

  17. #17
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    Quote Originally Posted by RJP Diver View Post
    Nonsense.
    Actual it's quite factual, given he tube failed in exactly the manner described. The replacement tube has a larger diameter at the valve.

  18. #18
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    Quote Originally Posted by B_arrington View Post
    Actual it's quite factual, given he tube failed in exactly the manner described. The replacement tube has a larger diameter at the valve.
    Trying to convince the internet that you're right is tough.

    Almost everyone here doubts your claims. I am one of them. I run a "18-25mm" tube in "32mm" tires. They've lasted over a thousand miles.

  19. #19
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    Re: 23mm tube in a 25mm tire? And presta values

    Quote Originally Posted by B_arrington View Post
    So I found out that its really not a good idea to run an 18-23 mm tube in a 25 mm tube. Turns out the part of the tube where the value is doesn't inflate like the rest of the tube. It creates a lot of stress and eventually cracks the tube. The tube only lasted about 5 weeks and 150 miles.
    Completly incorrect.

    a) tubes don't crack.
    b) There have been a lot of tube failures recently due to manufacturing problems - they split or get a hole approximately 1" from the valve. It's a defect unrelated to anything you or a shop has done.
    c) I use 18-23 tubes in my 700x28 tires, and have for years, because they're easier to install.
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  20. #20
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    Quote Originally Posted by B_arrington View Post
    Actual it's quite factual, given he tube failed in exactly the manner described. The replacement tube has a larger diameter at the valve.
    If it's factual, then obviously you should have experiments supporting that claim. After all, according to you it should be easy to replicate it based on predictions.

  21. #21
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    Quote Originally Posted by kjdhawkhill View Post
    Trying to convince the internet that you're right is tough.

    Almost everyone here doubts your claims. I am one of them. I run a "18-25mm" tube in "32mm" tires. They've lasted over a thousand miles.
    Nonsense.

  22. #22
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    I'm pretty sure I just hit the big blue "reply to thread" button on the bottom, as in adding on to this thread in the "general sense". I am very envious of both your free time and green shaft of reputation.

  23. #23
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    Quote Originally Posted by SBard1985 View Post
    I'm pretty sure I just hit the big blue "reply to thread" button on the bottom, as in adding on to this thread in the "general sense". I am very envious of both your free time and green shaft of reputation.
    But when you do that it looks like you replied to the post under which your post appears. It's confusing.

    I have been at this a few years. I do 100% of my posting in the evening and spend about an hour a day on bike forums. It beats the heck out of watching prime time TV.

  24. #24
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    Quote Originally Posted by Kerry Irons View Post
    I do 100% of my posting in the evening and spend about an hour a day on bike forums. It beats the heck out of watching prime time TV.
    Well played, Irons, well played.

  25. #25
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    Quote Originally Posted by SBard1985 View Post
    I'm pretty sure I just hit the big blue "reply to thread" button on the bottom, as in adding on to this thread in the "general sense". I am very envious of both your free time and green shaft of reputation.
    That is pure awesome...is it ok if I borrow that at some point?
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