Forum menu
Have you ever had a tubeless setup mysteriously deflate with no obvious cause?
Sometimes it retains its pressure for weeks. Then it waits till you have become complacent and deflates overnight. Reinflate, fine for ages, then when you're running late and grab the bike quickly - flat.
I've pumped it up to 30psi and dunked it in water (including entire valve) - not a bubble in sight.
I've retaped it and reinstalled tyre and sealant lthis morning. Fingers crossed!
The recent warm weather is causing thermal expansion of your rim and opening up a micro crack in the weld and letting air escape...
...maybe.
The only time I've had it happen, it was leaking from the valve...but sporadically as you describe. Over tightening the locknut actually made it worse. Changed the valve and it was fine. Some rim well shapes don't play nicely with certain valves.
Try wobbling the valve after spraying soapy water around it.
Last time I had similar, it turned out to be the tape. No obvious single spot but just seemed to weep through. Maybe the adhesive was off.
The rims are carbon so I'd say thermal expansion is unlikely? I bloody hope there are no micro cracks!!
Dodgy sporadic valve seal? Sounds feasible. Hopefully the retaping and reinstallation of the valve will sort it, if not, replacement valve.
Thanks
I've had it but I usually put it down to the sealant doing its job - you'll get a puncture halfway through a ride, but won't even notice it. It might not be perfectly sealed when it's in the shed though, and with no sealant sloshing about it deflates.
Certainly had issues with some valves sealing to the rims though so check that.
My rear does this. It is a gheto conversion with non-tubeless rims and tyres, a repurposed valve from an old tube, using gorilla tape and Stans sealant so I can't complain. Oddly the front doesn't.
Basically the rear tyre will slowly lose pressure over time. I just make sure I pump it up once a week or so.
Yeap had that. Was the tyre side walls. They weaped constantly and were always flat by the next ride.
I've had this and I put down to the glue on the tape cracking, now I use duct tape, much better. You could try using an inner tube cut down the center to seal the rim, makes a perfect seal if you can hook the tyre inside the tube.
Had a couple of thorn issues, big thorn goes in and gets auto sealed, then with time thorn dries/shrinks and pops out at a time to suit itself.
I’ve also had Similar happen with old large repairs that I was too lazy Do an inner mushroom fix on ......
^^ - what’s an inner mushroom fix? Is this something different to anchovies/Dynaplug?
Assuming you cant see a leak with a sealant puddle then I'd give them a new valve and re-tape to start.
🍄 plug patch is fitted to the inside of the tyre in the same way a car tyre is repaired.
If it repeatedly holds pressure nicely until it falls to a certain pressure (they all drop slowly) then drops rapidly I’d look at the tyre - particularly look for molding lines. They get compressed by the general pressure of the tyre but once that drops enough, they push open a route for escaping air. Maxis used to be bad for this.
The only time I’ve had it happen, it was leaking from the valve…but sporadically as you describe. Over tightening the locknut actually made it worse.
Had that then one day when I took valve core out it fell apart the little brass washer at the bottom of the valve was cracked...so doing it up was inaffective