Tubless tyre set up leaking air

Question

I am setting my bike up tubeless. I have been able to seat my tyre and can inflate to around 40psi, but air is leaking out the sides of the tyre quickly. How can I prevent this. Will they seal themselves eventually? Note these are not brand new tyres if that's the problem

Answer 1

Reading the question, it sounds like you are confident that the beads are seated. For everyone else's reference, when properly seated, tubeless tires are designed so that a line will show just above the rim lip. That line needs to be continuously visible. When I compared a Vittoria Corsa Pro with tubes and installed tubeless, the line wasn't as straight with tubes in the tire.

If the bead weren't seated, I would expect the tire to not hold air at all. I don't know if you could actually inflate it. I honestly have not experienced this in the single tubeless installation I did in person. I think you have to pump more air in faster to cure this. If you used a standard floor pump the first time, consider using something with more airflow, e.g. a tubeless canister or a CO2 cartridge - note that it's usually going to take an entire cartridge to seat a road tire, and I'm not sure how gravel or MTB tires do. (Note: if you use CO2 to seat, deflate the tire entirely before adding sealant. The seal won't break. CO2 can interact with some sealants in a way that you don't want.)

It's also possible that air is leaking through the casing. The symptom of this is that you'll see the casing appearing to sweat beads of sealant. Different tires have different leak rates; my Panaracer Gravelkings leaked sealant for a couple days, but I believe my Corsa Pros did not leak sealant from the sidewalls, even though that tire has very thin sidewalls. For this, you just keep inflating the tire and wait. Make sure to rotate the rim around to distribute sealant. This will eventually stop - or it should do so. Compass Tires' thinnest casing has been said (on forums) to just keep leaking, and some people give up and run them tubed. There might be a few more tires like that. If it really keeps leaking, I would approach the manufacturer and ask for a warranty or for technical advice.

Answer 2

Normally, I have had success with road tubeless installations by first inflating the tire dry (no sealant), where the tire would hold/maintain air pressure reasonably. I would follow this by deflating the tire, adding sealant, and re-inflating the tire, and it was ready to ride.

In very rare cases, I have needed sealant in the tire for the tire to seal on the bead/rim interface well enough to not quickly lose air pressure. The first time this occurred, it was baffling that this was the case as I had never seen this behavior before and the wheels I was setting up were those of a riding buddy of mine, using the same rim (Shimano Ultegra) and the same tire (Hutchinson Fusion 5) as I was riding, and had set up successfully numerous times. These rims do not need a rim strip (no spoke holes in the rim bed) so the leak was purely at the rim/bead interface (the valve was fine). I was using an air compressor to inflate the tire to 80 psi, but even with that, the tire would leak-down way too quickly. Repeated attempts resulted in the same quick leak-down result/failure.

The rim was fairly clean/clear of previous sealant, so it really had me baffled. It should hold air for a reasonable amount of time based on past experiences. I chose to add the sealant and try again, expecting the same result, albeit much more messy with sealant in the mix. To my surprise, just the addition of sealant (with of course moving the wheel around to ensure sealant hit the entire rim/bead interface) did the trick. The tire stopped having the quick leak-down issue.

Since then I have only come across this one other time, and the addition of sealant made the difference in having the tire seat and SEAL there as well. Regardless of whether a tire seats easily of with difficulty, I recommend going for a short ride on every newly mounted tubeless tire. The flexing of the bead area while under a rider's weight, along with the movement of sealant within the tire helps work sealant into any less than ideal areas that needs to seal.

It was also mentioned that the tires being mounted were not new, but used. If tire sealant was used, it is possible that remnants of old sealant was still on the tire beads. If the old sealant is uneven, leaving a bumpy, unsmooth tire bead, sealing will be difficult. Clean the tire bead of old sealant. Isopropyl alcohol on a paper towel or rag will clean it off with some effort. Be careful not to tear the tire bead by being too aggressive. Additionally, if the rim has been used tubeless before, ensure the rim interface where the tire bead rests is clean and smooth as well. Doing this will help ensure a successful sealing of tubeless tires.