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Thread: Tubeless tyres

  1. #1
    Senior Member coolboarder's Avatar
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    Tubeless tyres

    I've just bitten the bullet and splashed out on some Mavic Cosmic Pro Carbon SL UST wheels with Mavic tyres which is my first foray into tubeless. One reason I chose them (apart from the great value and review in 'The Comic') was that the tyres are included as part of an integrated package and already mounted (but without the sealant) to save me the hassle of fitting. First thing I did was inflate them without sealant and they lost pressure completely very quickly in 2 hours. So I put the sealant in one spun it around and pumped it up but it lost pressure again in 1-2 hours. Then just before bedtime I pumped it up again to 80 psi and left it overnight but this morning it had lost 20 psi - an improvement but not what I had expected.

    Questions: who else had experience of tubeless - or even these wheels and tyres? Shouldn't the tyre hold its pressure even without sealant and can I expect it to hold it for longer once the sealant has settled down?
    Last edited by coolboarder; 2 Weeks Ago at 10:13 AM.
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    Senior Member Boxhilljunkie's Avatar
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    I always thought the sealant was to stop the tyres from moving ...not to seal air in...
    ive never had tubeless ... I like the idea to them but can see trying to fix a puncture a total nightmare...my fatbike tyres are tubeless ready...but I still use a innie

  3. #3
    Senior Member coolboarder's Avatar
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    Quote Originally Posted by Boxhilljunkie View Post
    I always thought the sealant was to stop the tyres from moving ...not to seal air in...
    So did I, and to seal punctures of course, so I was surprised when they lost pressure so quickly.
    Quote Originally Posted by Boxhilljunkie View Post
    ive never had tubeless ... I like the idea to them but can see trying to fix a puncture a total nightmare...
    The reason I've resisted for so long, I imagine it would be impossible by the side of the road and I've heard a few horror stories. So once the pressure problem has been sorted I don't intend going far from home until I've gained confidence in them. I can always go back to HP tyres and tubes if I have to but I'm seduced by the potential of them being more puncture proof, lower overall weight and lower rolling resistance and I as I wanted a pair of lightweight flash carbon aero wheels this seemed the opportunity to go tubeless at the same time.
    Last edited by coolboarder; 2 Weeks Ago at 10:12 AM. Reason: typo
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    Senior Member VLAD (the Friendly Vamp)'s Avatar
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    I've heard that soemtimes they do not seal correctly to the rim if not blown up correctly and at high enough pressure. That could be the issue. Try taking them to a garage and using the HP air line. See if that helps to seal the tyre to the rim.
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    The key seems to be getting them to seal on the rim... there are special pumps which give a pressurised burst of air.

    I thought the sealant was to goop about and fill any holes.

    There is a tubeless guide in this months Cyclist mag, I'll have a read later, see if it offers anything useful. Nothing on youtube?
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  6. #6
    Senior Member coolboarder's Avatar
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    Quote Originally Posted by VLAD (the Friendly Vamp) View Post
    I've heard that soemtimes they do not seal correctly to the rim if not blown up correctly and at high enough pressure. That could be the issue. Try taking them to a garage and using the HP air line. See if that helps to seal the tyre to the rim.
    Quote Originally Posted by PRSboy View Post
    The key seems to be getting them to seal on the rim... there are special pumps which give a pressurised burst of air.

    I thought the sealant was to goop about and fill any holes.

    There is a tubeless guide in this months Cyclist mag, I'll have a read later, see if it offers anything useful. Nothing on youtube?
    I've blown them up easily with a track pump to 80 psi, the maximum recommended is 87. Go much higher and there is a danger of blowing the tyre off the rim which is hardly conducive to sealing the bead to the rim.

    This issue has been one of the reasons I've eschewed tubeless before but as the Mavic wheels come with the tyres factory fitted I would have assume that they had got this sorted for me.
    It doesn't matter how many times you fall down, its how times many you get back up that count.

  7. #7
    Senior Member The return of Marty Wild's Avatar
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    A mate has got them on his climbing wheels, absolute ballache to set up, but once you've got the knack and they're sorted, you're living the dream by all accounts.

    He had loads of hassle when he first got them. They tyres are super tight on the rim too are they not? The Mavic system where everything comes as a package does sound sweet!
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    Senior Member coolboarder's Avatar
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    Quote Originally Posted by The return of Marty Wild View Post
    They tyres are super tight on the rim too are they not?
    This is something that has put me off in the past - don't forget I struggle getting normal tyres off/on sometimes. I'm not tempted to try and lever them off to find out unless I have no choice as I wouldn't be happy in case I damage the rim or can't get them back on.

    Currently awaiting a mechanic from Sigma sports to call me back. I don't want to inflate them beyond the recommended pressure in case something goes wrong and it voids the warranty.
    Last edited by coolboarder; 2 Weeks Ago at 12:23 PM.
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    Quote Originally Posted by coolboarder View Post
    I've blown them up easily with a track pump to 80 psi, the maximum recommended is 87. Go much higher and there is a danger of blowing the tyre off the rim which is hardly conducive to sealing the bead to the rim.
    As I understand it, its not so much the pressure level as the speed with which the pressure is reached, which has the effect of making the seal (hence some suggest to use a compressor).

    I watched a GCN video, it did say that a tubeless system won't hold air as well as a tube, but 20psi loss overnight seems excessive.

    Maybe the seal will get better as you use it if you persevere. I assume you've fitted the tubeless rim tape.

    Or get one of these...
    https://www.evanscycles.com/speciali...CABEgLFrvD_BwE
    Last edited by PRSboy; 2 Weeks Ago at 1:51 PM.
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  10. #10
    Senior Member Boxhilljunkie's Avatar
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    According to Mavic ...if your using their UST tubeless tyres system, not only are your tyres superlight but you also don't need to use any tools to take the tyres off should you need to

    sounds pretty cool http://road.cc/content/tech-news/224...on-wheel-range

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