Tubeless Tire goes flat overnight

Hello fellow TR members,

I recently got a new pair of mavic aksium elite ust. This is my first time going tubeless. I noticed my front tire would gradually go deflated overnight if I just put it aside and it goes flat in a few days. However, I don’t seem to encounter any leaking issue when I go out for a ride if the tire is fully pumped up. I went out for a 4 hour ride yesterday and it was still well pumped when I got back. This morning, it’s only half-pumped though.

I injected 30ml of sealant when I first set it up 3 weeks ago. Does this have something to do with the tire itself or sealant? Thanks.

have you tries putting soapy water all over the tire to see where the leak is coming from? it could be in the sidewall, along the bead, the valve or the tubeless tape.

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check your sealant, a couple months ago I put on a new set of tubeless tires and needed to add sealant after a week or two (noticed they were quickly losing air). Was surprised at how much sealant had coated the inside of the tires! To do that:

  • take the tires off bike
  • suspend tires
  • remove valve core
  • insert “dipstick” and check on sealant level (like checking engine oil in a car)
  • add sealant if needed

Helps to have a dipstick and mark level after installing the tires, so you know the level when full.

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Some slow leaks are easier to detect by submerging the wheel/tire into a tub or bucket of water. Be patient, and if you see bubbles, even tiny ones, that is the source of the leak.

Pro tips from the early days of tubeless:

  • add a little bit more sealant for initial set up. Makes life so much easier.
  • Inflate tire to minimum ridable pressure, it should wobble. Ride around your house. This will strech the sidewalls, small leaks will pop up, sealant can reach this leaks.

And something like Caffeelatex makes life so much easier as well. The foaming agent helps getting those small leaks.

And there is a learning curve with tubeless …


Soapy water in a spray bottle is useful to find small leaks. Overnight, I would put money on leaking around the valve and it’s the rim tape

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Agreed, my slow leak experiences have all been tied to valves that just don’t sit right inside the rim bed.

I’m running some Orange Seal valves on a set of road wheels now and they came with a couple sets of differently shaped grommets. Round ones would pull through the valve hole little by little and would start to leak, but more rectangular ones sat flush and sealed up tight.

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There are three main reasons for initial tubeless “failure”:

  1. the tape rim is fitted incorrectly or has been damaged.
  2. the tyre isn’t seated properly.
  3. See point #1

Often when the “valve” leaks it’s really the tape that’s been damaged and the air has just found its way round to the valve to escape.

Tubeless can be frustrating with an identical tyre/rim combo working on one wheel and not on another - I’ve had tyres stay up for several days without adding sealant yet the same tyre on the same rim won’t stay inflated for an hour. In those cases I always go back and strip off the tape, clean the rim and apply new tape.

Once I’ve got the tyre on and inflated then I go for a ride, only has to be half an hour or so, to help work the tyre bead into the rim and get the sealant into all those nooks and crannies. Do that and it’s then weeks before I need to check the pressure again.


Thanks all, mine was the valve core leaking in the valve found after spraying on soapy water. A couple of twists of PTFE cured it