How airtight should my tubeless setup be pre sealant?

_Bones
_Bones Posts: 8
edited October 2018 in Workshop
HI all,
Just dipping my toe into the world of road tubeless and have a question that I haven't managed to find a satisfactory answer for.

How airtight should my (non UST) tubeless setup be pre sealant?

I have my tyres on and mounted no problems but being curious I inflated the tyre to ~60 PSI without adding any sealant. The bead seal seems good but there is enough air escaping from around the valve and through a couple of spokeholes that the tyre (700x35c) was pretty much flat after about 5 minutes.

Is this to be expected? I had another go at taping and got the same result. Should I not worry and just crack on with the sealant?

Thanks all

Comments

  • Killerclown
    Killerclown Posts: 110
    _Bones wrote:
    HI all,
    Just dipping my toe into the world of road tubeless and have a question that I haven't managed to find a satisfactory answer for.

    How airtight should my (non UST) tubeless setup be pre sealant?

    I have my tyres on and mounted no problems but being curious I inflated the tyre to ~60 PSI without adding any sealant. The bead seal seems good but there is enough air escaping from around the valve and through a couple of spokeholes that the tyre (700x35c) was pretty much flat after about 5 minutes.

    Is this to be expected? I had another go at taping and got the same result. Should I not worry and just crack on with the sealant?

    Thanks all

    The sealant is there only to seal punctures. If your tyre is going flat, you have not got a satisfactory seal on the tyres and / or tape. Put some sealant in, and pump up the tyres, you’ll soon see where the leaks are. Tubeless tyres are notoriously tricky to get to seat satisfactorily without an initial air charge. You can get special pumps that can do this.
  • haydenm
    haydenm Posts: 2,997
    If there is air coming out of around the spoke holes and valve then it sounds like it's not taped properly. More tape should do it. I'm sure the sealant could potentially plug some small gaps by the valve but coming out of the spoke holes sounds a bit suspect. When I did my MTB the other week I didn't try it without sealant but it took a few days and a couple of rides before it stayed inflated overnight, that could have been due to the tyres having been run with tubes in previously though
  • CitizenLee
    CitizenLee Posts: 2,227
    If the beads snapped into place ok then it’s likely that you’ve haven’t got a good seal on either the valve or the rim tape, so I’d start again before trying with sealant to avoid a messy job later if they still fail to hold air.

    I actually converted my Cube to tubeless last night (tubeless tyres with non-tubeless rims) and tested them without tubes or sealant first, and surprisingly enough they inflated easily without issue. One thing I did do though, was to pop a drop of sealant on the rubber bungs on the valves, and then tightened the lock nut pretty tight. Once inflated to 50psi (they’re 38mm tyres, hence lower pressure) I did get some air escaping from the welded join in the rims, but this sealed itself once I put the sealant in, along with a few drops of sealant on the outside of the rim weld too. I then lathered the sidewalls in soapy bubbles to form an air barrier and left them over night. Thankfully when I woke up this morning and they hadn’t lost any air.

    So yeah, do the tape and valves again and see if they hold air this time ;)
    Current:
    NukeProof Mega FR 2012
    Cube NuRoad 2018
    Previous:
    2015 Genesis CdF 10, 2014 Cube Hyde Race, 2012 NS Traffic, 2007 Specialized SX Trail, 2005 Specialized Demo 8
  • _Bones
    _Bones Posts: 8
    Thanks folks I'll break out the tape (again!)
  • svetty
    svetty Posts: 1,904
    The valves should almost seal if you tighten the lock-ring enough. Once you've done this I'd add the sealant. Given that you've checked the taping is done properly this should seal any residual small leaks.
    FFS! Harden up and grow a pair :D
  • _Bones
    _Bones Posts: 8
    I may have found the problem. The tapered rubber seal at the top of the valve really doesn't engage into the valve hole on the inside of the rim, even without tape in the way. It's as if the valve is a little too big for these rims. Are there valves out there known for their particularly slender seals?
  • zefs
    zefs Posts: 484
    Press the rubber seal of the valve downwards a bit to help it move further down and then tighten the lockring (without letting go of the rubber seal), does that help?
    You can also use a tube overnight to help the tire seal better but shouldn't be needed if done right on a proper system.
  • cycleclinic
    cycleclinic Posts: 6,865
    Do what I do. Get a rubber mallet and tap firmly the valve rubber into the rim. Then get the collar tight. Works every time. also use. Sharp point to pierce the tape then use the closed valve pushing down to open up the hole. This way you won't tear the tape.

    Leaks from the spoke holes means bad taping. Retape
    http://www.thecycleclinic.co.uk -wheel building and other stuff.

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