Advertise on Bikeforums.net



User Tag List

Results 1 to 14 of 14
  1. #1
    Senior Member
    Join Date
    Jul 2009
    Location
    Montreal
    Posts
    111
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Tube too small ?

    Strange thing happened to me today.
    Yesterday i changed my tube because the former one was no longer patchable (damn glueless patches).
    My tire is a 700x25c, so i put a bontrager 700/18-25 tube and start to pump. The tube doesn't seem to fill the tire very well but i haven't reach the recommanded pressure yet, so i keep pumping to 90psi... Looks good.
    This morning i take my bike, and i feel a bump every wheel turn. Now i have spend half an hour trying to put the tube and tire back to place but the only thing i can do is move the tire bump. It seem that the tube isn't pushing the tire radially enough to place the tire beads in the bead sits, causing an unround tire.

    Tonight i will swap tube, but have i done something wrong with this one ?

  2. #2
    Primate Metzinger's Avatar
    Join Date
    Jan 2006
    Location
    gone
    My Bikes
    Concorde Columbus SL, Rocky Mountain Edge, Sparta stadfiets
    Posts
    2,582
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The rubber at the valve stem may be caught under the bead.
    Are you using the valve stem nut?
    Undo it, deflate the tire, push the stem into the rim then reinflate.
    Most users of that type of valve don't use that nut anyways.

  3. #3
    Senior Member
    Join Date
    Jul 2009
    Location
    Montreal
    Posts
    111
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yeah, i have thought of that, so i deflated, pushed the valve in, checked both sides of the beads to make sure the tube wasn't pinched and reinflated, but i still have a bump somewhere on my tire.

  4. #4
    Primate Metzinger's Avatar
    Join Date
    Jan 2006
    Location
    gone
    My Bikes
    Concorde Columbus SL, Rocky Mountain Edge, Sparta stadfiets
    Posts
    2,582
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    A too-narrow tube wouldn't cause that.
    Maybe the tire casing has been damaged.

  5. #5
    Senior Member
    Join Date
    Jul 2009
    Location
    Montreal
    Posts
    111
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    i'm not sure i've been clear enough, so here are a few more details :
    1) The bump is caused by the beads being too much inward, resulting in a lower tire
    2) By replacing the tire i can move the bump around but can't seem to remove it
    3) The tire is a pretty new Continental ultra sport, which has never done that before

  6. #6
    Real Men Ride Ordinaries fuzz2050's Avatar
    Join Date
    Sep 2008
    Posts
    3,621
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I'm pretty sure it's not the tubes fault, if only because I'm running the same width tube in my 35mm tires to no ill effect.

    Just an idea, is this on a fixed gear bike that gets a lot of skidding?

  7. #7
    Senior Member
    Join Date
    Jul 2009
    Location
    Montreal
    Posts
    111
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    that's a fixed gear bike that takes no skidding

  8. #8
    Senior Member CACycling's Avatar
    Join Date
    Feb 2008
    Location
    Oxnard, CA
    My Bikes
    '08 Fuji Roubaix RC; '07 Schwinn Le Tour GS; '92 Diamond Back Ascent EX
    Posts
    4,388
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    90 PSI may not be enough to seat the tire. I've got one set of rims that take over 100 PSI before the beads seat properly.

  9. #9
    Senior Member
    Join Date
    Jul 2009
    Posts
    149
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    tyre bump

    I ended up swapping tyres over between 3 bikes (don't ask) and found that two sets of wheels accepted all 3 sets of tyres with the bead even all round. However, the F.W.Evans bike (with, I presume, Evans own wheels) had the problem you describe. the bead was even for 90% of the circumference, but the bead disapeared into the rim for the remainder. My mate, who has more patience than me spent about 20 minutes on each wheel until he had an even bead all round. I had never had this problem before. One final thought, I'm pretty sure the wheels were original equipment on the bike (Evans have a good reputation for their wheels) but they were specced in the catalogue as having 28 section tyres and we were fitting 23 and 25 section. Another thought, could the Evans wheels have been 27"? We were fitting 700C......

  10. #10
    Senior Member
    Join Date
    Jul 2009
    Location
    Montreal
    Posts
    111
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by aljohn View Post
    One final thought, I'm pretty sure the wheels were original equipment on the bike (Evans have a good reputation for their wheels) but they were specced in the catalogue as having 28 section tyres and we were fitting 23 and 25 section.
    That may be part of my problem as well. My rims (ZAC 19) are rated 28-38, but since the bike came with 25 tires, i've always put 25.
    It is the first time i've had this problem although many tube change, and that's why i blame the tube

  11. #11
    Guest
    Join Date
    Jul 2008
    Location
    Grid Reference, SK
    My Bikes
    I never learned to ride a bike. It is my deepest shame.
    Posts
    3,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It is not the tube's fault.

    Make sure the tire bead is seated as well as possible, and that the tube is not pinched between the rim and tire, then pump it up to 125 psi... it should seat itself.

    If it does not seat itself at higher pressure, deflate to ~30 psi and try to pull out all the low spots. Eventually you will get it round.

  12. #12
    Map maker cbchess's Avatar
    Join Date
    Feb 2008
    Location
    Richmond,VA
    My Bikes
    Ventana El Ciclon, Walt Works 29er, Specialized Enduro (fixed up for my son).
    Posts
    730
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    you just haven't seated the bead correctly. you can pull the tire with your hands and massage the bead into place - you might have to lower the PSI to do it.

    I run 26" tubes in my 29er wheels and have no trouble its not the tube, its the operator.

  13. #13
    Senior Member
    Join Date
    Jul 2009
    Location
    Montreal
    Posts
    111
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by CACycling View Post
    90 PSI may not be enough to seat the tire. I've got one set of rims that take over 100 PSI before the beads seat properly.
    Quote Originally Posted by LarDasse74 View Post
    It is not the tube's fault.
    Make sure the tire bead is seated as well as possible, and that the tube is not pinched between the rim and tire, then pump it up to 125 psi... it should seat itself.
    This worked, thank you. I thought 90psi would be enough pressure to seat the beads but it wasn't.

  14. #14
    Guest
    Join Date
    Jul 2008
    Location
    Grid Reference, SK
    My Bikes
    I never learned to ride a bike. It is my deepest shame.
    Posts
    3,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    90 Psi should be about the lowest pressure you ever run in 700X25 tires... Those tires probably have a pressure rating of 125, and can take much more.

    PS I just looked at the Continental website and the reccomended pressure is 95 PSI and max pressure is 120.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •