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Tyre slipped off rim - what now

TjgoodhewTjgoodhew Posts: 628
edited February 2014 in Road general
Iv just got back from a ride cut very short due to my front clincher slipping off the rim.

The wheels are campy zondas and the tyre is a vredestein tri comp. the tyre is about 1500 miles old and has never done this before

I was coming to a junction after a short but fast climb out of the saddle. I was pulling away and it felt like the front wheel slipped and very nearly threw me off

The tube didn't blow and I went straight home to check everything. The tyre, tube and wheel all seem fine and I have remounted and inflated back up to 100psi with no issue

So what now ? Just ride and forget about it ? My concern is that if the same thing happens at high speed I could be in a lot of trouble
Cannondale Caad8
Canyon Aeroad 8.0

http://www.strava.com/athletes/goodhewt

Posts

  • cougiecougie Posts: 22,512
    Seems very odd - but for the sake of £30 I'd get a new (different make) tyre and use that on the front.
  • That is strange and really dangerous, personally I won't ride on it.

    Was it seated properly before the ride? I would contact Vredestein and see if they know of any conditions that could cause this. If have heard of tubs rolling off but not clinchers slipping off.

    Is the tyre beading OK?
  • rolf_frolf_f Posts: 15,959
    I don't see how this can happen! If the inner tube is fully inflated, the tyre is effectively locked to the rim. It's not even as though this was a rear wheel and (theoretically at least) capable of of being spun. All you can do with the front is somehow skid the front with the brakes on.
    Faster than a tent.......
  • I have had the same thing happen in the alps, just after some serious speed coming down Alp D'huez, was not the heat, was about half an hour after hitting the bottom. I think with a loose fitting tyre you must be sure tyre is central on rim when pumping up. Purchased a new tyre when I got home though.
  • gaz047gaz047 Posts: 601
    glad you weren't injured. the minimum recommended pressure for tricomps is 115psi iirc. If you were only pumping them to 100psi, perhaps this was the cause or part of the cause?
    if it ain't rainin.....it ain't trainin
    Stick your 'rules' up your a%se
  • All it can be really are damaged rim (bent from impact or worn rim so it's flexing out when under pressure), too little pressure in the tyre or damaged/poor tolerance tyre (slightly too big or bead damaged in some way).

    No matter which I'd not be trusting that tyre again!
  • rolf_frolf_f Posts: 15,959
    foggymike wrote:
    All it can be really are damaged rim (bent from impact or worn rim so it's flexing out when under pressure), too little pressure in the tyre or damaged/poor tolerance tyre (slightly too big or bead damaged in some way).

    No matter which I'd not be trusting that tyre again!

    It only makes sense not to trust the tyre if the cause of the problem is the latter. If the cause is the rim then there is no reason to assume that the tyre isn't fine subject to inspection.

    As Gaz says, these tyres have a madly high minimum inflation pressure though it still seems hard to credit that this incident could be a result of 15 psi under-inflation.
    Faster than a tent.......
  • This happened to me last year coming down into Meltham at a rapid rate of speed. The tyre just jumped off the rear rim and the inner tube popped out the side with an almighty bang.

    I did notice afterwards that the rim had a small dish in it on both sides of the rim, although I couldn't say whether this had occurred as a result of the incident, or something that was present prior to the event that I hadn't noticed. This dishing was very minor.

    Still bloody scary though, just glad it wasn't my front wheel as I would have been off!
  • sungodsungod Posts: 12,677
    as above, if the tyre was off the rim, the inner tube would have been unsupported at that point, surely an inner tube at anything close to 100psi is going to escape and burst

    it seems more likely that the inner tube had lost pressure, perhaps a faulty/dirty valve

    this would leave the tyre seriously under-inflated, subjected to load it could unseat
    my bike - faster than god's and twice as shiny
  • Thanks for all the comments.

    I did a bit more research and i read about the 115psi but as mentioned im not sure this could have been the reason. I have been running them at 100psi pretty much since iv owned them, The strange thing as well was the tube didn't burst.

    I did however go and have a look at where it happened last night and there is a distinct sink in the road surface. All im thinking is the wheel "missed" the road surface ( the only comparison i can think of is where you walk downstairs and go to step on another stair that isnt there) and this jolt caused an unusual flex in the wheel popping the tyre off.

    I have replaced the tyre with a GP4000s but is there anything i can check to make sure the wheel isnt the problem??
    Cannondale Caad8
    Canyon Aeroad 8.0

    http://www.strava.com/athletes/goodhewt
  • If the tyre is at 100psi inside the tyre the volume is restricted. In a free environment, the the pressure in the tyre would reduce in proportion to the volume of the tube. It therefore would expand but may not burst if the pressure is sufficiently reduce to a point where the elasticity of the tube is in equilibrium with the pressure inside the tube. I am not sufficiently good at physics but my quick calc suggests that when the volume of the tube in free air is twice that of the tube inside the tyre, the pressure in the tube is only half that of the original. Therefore, it is conceivable that the tube may not burst unless subjected to some other mechanical damage.
    I have only two things to say to that; Bo***cks
  • sungodsungod Posts: 12,677
    ^^^this calls for experimentation...

    freestanding wheel, partially off tyre and inner tube inflated to the point where it's only just held

    after a few beers, apply co2 inflator and see what happens

    if there're enough cartridges it could form the basis of a russian roulette-like game
    my bike - faster than god's and twice as shiny
  • @ Rolf

    I agree that's a sensible conclusion but unless I was 100% sure I knew what had happened I'd not be messing about. I certainly wouldn't want a tyre that had to be over 115psi either way.
  • DiscoBoyDiscoBoy Posts: 905
    If the tyre is at 100psi inside the tyre the volume is restricted. In a free environment, the the pressure in the tyre would reduce in proportion to the volume of the tube. It therefore would expand but may not burst if the pressure is sufficiently reduce to a point where the elasticity of the tube is in equilibrium with the pressure inside the tube. I am not sufficiently good at physics but my quick calc suggests that when the volume of the tube in free air is twice that of the tube inside the tyre, the pressure in the tube is only half that of the original. Therefore, it is conceivable that the tube may not burst unless subjected to some other mechanical damage.

    Yep, doubling the volume halves the pressure according to the ideal gas law:

    PV=nRT

    Where P and V are pressure and volume respectively, and nRT is all constant in this case (and they are the amount of gas, the gas constant and the temperature if you are interested).

    As for why your tyre came off the rim, I've no idea. But I'd be checking the tyre and rim closely before riding either.
    Red bikes are the fastest.
  • term1teterm1te Posts: 1,462
    I know of a tyre being blown off a rim. My son built up a bike for a school project, which was going to be shown at a parents' evening. First thing on a very cold morning we pumped the tyres up to 120psi. The bike was taken to school and left in the nice warm reception area. An hour or so later there was a massive bang, which was traced to his front wheel. The inner tube was in shreds and one bead of the brand new tyre was blown off the brand new rim. I guess the curse of Boyle had struck with the pressure in the tyre increasing with the temperature until it blew the bead over the edge. I've done something similar which destroyed the, very worn, rim, fortunately when I wasn't on the bike. The moral is don't inflate your tyres when it is -5C.
  • This thread makes for interesting reading. I too had a TriComp go BANG!! and roll off the rim, the thread on the sidewall had really torn up. Fortunately, I was only 5km walk home. I was running circa 100psi (115 is excessive for a 66kg rider in winter!).

    A shame, as they are a fantastic tyre, but that experience has put me off. Less than 500km ridden on them.
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