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Tubeless air loss

navrig2navrig2 Posts: 1,616
edited November 2016 in MTB workshop & tech
I have a bike with 27.5" wheels and fairly fat tyres. They came as tubeless. For various reasons the was used a bit in the spring and left idle over the summer into the autumn (I mostly ride road). Today I decided I'd give it a short ride.

So after several months doing nothing but sitting in the garage the tyres were soft but not flat. I could have riden without the rims touching the road. I pumped them back up to 50psi (I wasn't planning leaving the road) and set off. I popped into a friends for 30 mins and when I came out the rear was flat (as a pancake). I borrowed his pump and set off again. About 4 or 5 miles later the rear felt spongy and, sure enough, it was softening. Shortly after that it was flat and I had a long walk home (no pump!!).

I pumped it up again and left it. The tyre is now flat again.

I've not had tubeless before so this is all new to me.

Why is the rear now flattening in 30mins when it just softened over a period of months?

What do I do to stop it (other than fit a tube!)?


  • The lower the pressure, the slower the air escapes. When you sit on the bike, it's guaranteed to go out faster.

    If it was mine, I'd check sealant, pour some new in, and re-seat the beads.
  • navrig2navrig2 Posts: 1,616
    I suspect you may be right. Thanks for your quick response.

    I may out a tube in!
  • navrig2navrig2 Posts: 1,616
    The bike is only 10 months old. How long is sealant meant to last?
  • cooldadcooldad Posts: 32,601
    Have a look and see. Might be a solid blob by now having not been used.
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  • navrig2navrig2 Posts: 1,616
    cooldad wrote:
    Have a look and see. Might be a solid blob by now having not been used.

    Will do. Meantime as I want the bike for Saturday I'll buy a couple of tubes.

  • andy9964andy9964 Posts: 930
    Is there rim tape ?
    I converted some Archetype rims, and the air leaked out under the tape
  • navrig2navrig2 Posts: 1,616
    Andy9964 wrote:
    Is there rim tape ?
    I converted some Archetype rims, and the air leaked out under the tape

    The wheels haven't been "touched" since I bought the bike new. The tyres were still under pressure after a few months of doing nothing. Total loss of air started after I pumped them up.
  • navrig2navrig2 Posts: 1,616
    So I bought a couple of tubes full intending to convert away from tubeless.

    Before doing the deed I gave rear one more chance. Took the wheel off the bike and pumped to 50psi. I then gently spun it for a few minutes. Left it overnight.

    Next morning it was still solid.


    Anyone want to but a couple of tubes!?
  • Are you sure its set up tubeless and not with tubes, they usually come with tubes even if tubeless ready? could be a puncture?
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  • navrig2navrig2 Posts: 1,616
    Definitely tubeless. On the first ride I had to let air out of the tyres to get it onto the roof rack. When I re-inflated there was some minor fluid leakage from around the rim. I wasn't too impressed as I chose the tubed option when I bought the bike.

    I't's been sitting at a decent pressure now since Saturday when I did a 40 mile X-country ride. No puncture.
  • lpretro1lpretro1 Posts: 237
    Usually need to top up sealant every 6 months or so
  • navrig2navrig2 Posts: 1,616
    lpretro1 wrote:
    Usually need to top up sealant every 6 months or so

    Do you?

    I'll investigate.

    Still not convinced that tubeless is worth it.

    That said the tyres are holding pressure even what the bike is not in use.
  • I'm pretty new to tubeless ... and not entirely sold on it.

    My rear is a tubeless ready rim, fitted with a wire-bead Maxxis Ardent. The sidewalls are locked on solid, so much so that when I recently tried to remove the tyre to investigate a persistent hole that wouldn't properly seal, I couldn't get the tyre off the rim. Not sure what will happen if I get a flat out on the trail that doesn't seal and I need to get an inner tube in!

    Its been running fine for a few months but developed a slow-ish leak a few weeks ago that the sealant wouldn't plug properly. Finally got round to checking it out yesterday, and pulled out an inch long thorn ... so that'll be why I guess.

    The front is a standard rim, fitted with a TR On One Chunky Monkey. Its a bit of a baggy fit, but went up tubeless OK when I had it done a few weeks back, but then lost all the air over the course of a few days left unused in the garage. Took the tyre off to check for thorns / glass etc, found none, re-fitted and eventually re-seated the tyre, reinflated to find air bubbles leaking from the valve. Spent ages last night sloshing sealant around the valve area, reinflating, spinning the wheel, and still leaking. So will now have to take it all off, clean it up, get a new valve and tape, and start the whole process again. It did occur to me that 5 minutes would have seen an old inner tube taken out and a new (or repaired) one put back in.

    I know the claims, about running lower pressures, more supple side-walls, reduced risk of snake-bites etc ... but its not fail-safe in my experience, and I wonder whether the faff and the mess are really worth it when things don't quite go to plan with tubeless set up. Will persevere ... but I reserve the right to return to tubes if it doesn't work out for me!!
  • POAHPOAH Posts: 3,369
    don't pump tubless set ups to 50psi as its likely to blow the tyre off the rim. don't go above 40psi
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