New (to me) Tyre Problem

meanredspider
meanredspider Posts: 12,337
edited April 2011 in Workshop
This morning I had a tyre problem I've not experience before in my 40 years of riding a bike

Basically a few inches of the sidewall of the tyre popped out of the rim exposing the inner. Fortunately (esp given the tyre was inflated to something like 120psi) I just stopped, deflated the tyre, popped the tyre back in the rim, reinflated and set off again. But I'm no nearer understanding why it happened. Overinflation? Tyre not properly fitted?

Tyres are 25c Gatorskins on Shimano RS80 carbon/ali wheels with (IIRC) 18-25 Spesh inners. It was a front tyre. I've already done around 150 miles since I last had the tyre off the rim so a pinch on assembly I'd have thought would have showed up before now.

Thoughts please
ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH

Comments

  • rhext
    rhext Posts: 1,639
    The only time I've ever seen this was when I stretched the tyre wall with a bit of ham-fisted fitting using tyre levers. The guy at the bike shop was very good in that not only did he explain to me what I'd done wrong, he also replaced the tyre anyway....but after that I've never used tyre levers to fit a tyre again.

    My only guess if the tyre itself is not damaged is that the bead wasn't properly seated on the rim.
  • Berk Bonebonce
    Berk Bonebonce Posts: 1,245
    Both rim and tyre manufacturers do not work that closely to tolerances and standards. I would suggest that you might have a naturally large diameter tyre on a naturally small diameter rim.
  • meanredspider
    meanredspider Posts: 12,337
    The tyre wasn't an easy fit. I may have put too much air in the tube before I fitted the tyre and maybe the bead didn't settle properly. Just never had this happen before and it's slightly disconcerting - recipe for a big blow-out at speed.
    ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH
  • Crapaud
    Crapaud Posts: 2,483
    How are the rims? Are they a bit worn? It's possible that having the tyres at 120psi has pushed the rims outward leaving room for the tyre to pop off.

    Apart from what Berk Bonebonce says, that's all I can think of.
    A fanatic is one who can’t change his mind and won’t change the subject - Churchill
  • Monty Dog
    Monty Dog Posts: 20,614
    If you've got the tyre seated too deeply on one side, then it's possible for the bead to lift on the other side - done it a couple of times over the years - simply deflate and reinflate. FWIW I've never seen a tyre bead 'stretch'
    Make mine an Italian, with Campagnolo on the side..
  • rhext
    rhext Posts: 1,639
    Monty Dog wrote:
    If you've got the tyre seated too deeply on one side, then it's possible for the bead to lift on the other side - done it a couple of times over the years - simply deflate and reinflate. FWIW I've never seen a tyre bead 'stretch'

    Old fashioned steel tyre levers, cheap tyres and a little over-enthusiastic fitting.... You couldn't see any damage, but there was obviously a weak spot on the bead because it kept popping off the rim in the same place. I just assumed I'd damaged it because that's what the guy in the bike shop told me was the most likely cause. And since he replaced the tyre anyway, and because I was just a kid, I wasn't going to get into any prolonged discussion with him!

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