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Tubeless Question

loukestloukest Posts: 89
edited May 2016 in MTB workshop & tech
Hi,

This is killing me.....Having worked in a bike shop for many years (prior to tubeless being available), I consider myself a decent bike mechanic and can't remember the last time I had to take a bike to the shop, however, I can't for the life of me figure this out. I have a new MTB, when I picked it up, I asked for the tubes to be taken out and tubeless valves put in on the basis that both the rims and the tyres were UST ready. The front is fine, the rear just keeps going down. I've had it in the bath with me and the air is coming from the valve, more specifically, where the nut touches the rim on the outside. I realise that I should just take this back but the shop where I got it from is miles away (long story). I bought some new valves and am having the exact same problem. When I look at it closely, the valve hole is not central on the rim, that means that where the valve comes out of the rim on the side of the rim where you would attach the pump, the small nut that attaches to the valve stem is slightly wider than the rim on one edge (due to the hole not being central on the rim). The rims are SRAM Roam 30. In short, I just can't see how you could ever get a decent seal. I've checked the diagram that comes with the valves a number of times to make sure I have the rubber washers in the right place etc.

Has anybody seen this before, am I missing something?

Thanks in advance, Tom

Posts

  • The RookieThe Rookie Posts: 27,747
    The seal is on the inside, the nut just compresses it, so I can't see how the issue on the outside affects it at all?
  • Escher303Escher303 Posts: 342
    As the Rookie says the seal of the valve is against the tape and rim hole on the inside so the fact that the nut doesn't seal on the outside of the rim is not the problem. However if the tape and inside of the rim is not sealed properly the air will leak out through the path of least resistance, maybe a spoke hole, or more likely through the valve hole.

    So you've got air escaping from inside the tyre, underneath the tape, into the rim bed and out through the non-sealed part of the valve hole. Try retaping, putting a tube in, inflating it and leaving for several hours for it press the tape down firmly then try again. Having the correct width tape helps as the bead of the tyre is less likely to lift the edges of the tape.
  • RockmonkeySCRockmonkeySC Posts: 15,247
    Have you fitted rim tape?
  • duskdusk Posts: 583
    OP has me confused by saying UST ready, are the wheels UST or tubeless ready? If the latter then as above.
    YT Wicked 160 ltd
    Cotic BFe
    DMR Trailstar
    Canyon Roadlite
  • loukestloukest Posts: 89
    Hi, thanks for the response, all comments absolutely valid. I spoke to the shop, they had initially told me that I didn't need rim tape on these rims, they've since looked into it and spoken with SRAM, apparently, there is one model in the ROAM range that needs tape and this is it. I put tape on, all sorted. Thanks again.

    Tom
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