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This question is a follow up this question: Used tubeless ready tires leaking air (that were used previously with tubes)

I'm trying to get a 'working tubeless' system, and the pressure keeps dropping (10psi/0.5 bar per day).

I'm wondering if I missed some important step:

  • the wheels are from Mavic and the tape was fitted in the factory. I used the valves provided with the wheels. The tires are tubeless ready, from Michelin.
  • the tires were mounted without sealant. I could seat them with a foot pump, and heard the 2 "pangs" when mounting them. I inflated them till 4.5 bars before emptying them and removing the valve core.
  • I initially followed Mavic recommendation for the sealant and added 45ml per wheel, shaked the wheel to try to spread the sealant, then went for a 5km ride on gravel. A note about the quantities: I didn't pay attention to a detail, Mavic's recommendation is for UST tires, which means "tubeless", not "tubeless ready", so the sealant is only used for punctures.
  • following the previous question's answer, I emptied my bottle of sealant (that's 120ml in total), try to spread the sealant in the tire, then went for my 5km gravel ride.
  • I repeated this step a few times, and now have 220ml in the 2 wheels (40mm tires), after having purchased another bottle of sealant (same brand).
  • I went for a 20km "medium" MTB trail (pressure about 3bars), with loads of root and cobbles stones) in order to spead the sealant.
  • I went for a 25km road/gravel ride (4 bars).
  • I took a small nail, put it in the tire and removed it, to see if the sealant works, which it did.
  • There's still sealant in the tires, and I'm only using a foot pump, no CO2.

After this, pressure is still dropping overnight. After spraying soapy water on the tires, it is possible to see that there are still many leaks through pores (see picture) — the front wheel is better, but not perfect. mushrooms of soap forming on a bike wheel. Also, I spotted some leaks around some tires marking, that are still there (it's not new holes then). No bubbles are forming next to the rim's interface (bead and valve).

Is it normal, and if yes shall ride more (Schwalbe recommendation is 25km, I think I rode more...) or shall I keep adding sealant, or is it possible that the sealant is just not suited for this kind of tire (not fluid enough to get into the pores)?

[EDIT]

After an additional 75km on rough surface and no progress on the "soapy water test", I decided to have a look inside. As pointed by Nathan Knutson and MaplePanda in the comments, there were serious doubts about the sealant used (Mavic, only certified for true tubeless tires, not tubeless ready tires). But in all cases, I got back almost 200ml of sealant. Strangely, on the other tire (front), the sealant was more evenly spread.

inside the tire

The second picture shows the inside of the tire after having passed a soft cloth (no rough cleaning then).

This can also go into Andy P's suggestion: the inside of the tire was not clean enough and the sealant could not attach itself to the tire.

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    This is interesting. As far as I know, some weeping of the sealant through the tire's sidewall is OK. The amount you show in the photo does seem like there's a lot of sealant leaking through. This could be a deficit in the tire construction, but we don't know that. I don't know that any particular brands of sealant are more problematic than others. I am under the impression that normally the weeping behavior stabilizes after a couple days.
    – Weiwen Ng
    Oct 12, 2021 at 17:15
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    @WeiwenNg what you see from the picture is not sealant, it's bubbles from soapy water that I sprayed on the wheels to locate leaks.
    – Renaud
    Oct 12, 2021 at 18:02
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    Thanks for clarifying! In that case, I concur with @JoeK that what you see is probably within what you can expect for thin high-performance tires. I agree that the pressure loss should go down over time.
    – Weiwen Ng
    Oct 12, 2021 at 18:21
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    @Renaud Personally I have had good results with Stans sealant on ghetto tubeless wheels, so much so that it seems strange to me that your tyres would still leak that much air after pouring so much sealant into them. Sidewalls may be thin, but I have had punctures in mine and never leaked that much after the sealant settled. Might be worth trying another brand. Oct 13, 2021 at 9:06
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    Seeing the combination of that much air loss out the casing even with liquid sealant sloshing inside is interesting to me because it's the opposite of what I've observed with Stan's or Orange in similar tires. I wouldn't want to rush to blame the Mavic sealant but I kind of suspect it's less effective than those brands, at least in this application. Oct 13, 2021 at 17:46

2 Answers 2

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What you are seeing is normal for performance tyres with thin-as-possible sidewalls.

They won't stay porous forever, but you should inflate to your intended pressure before every ride for as long as it takes. You may never achieve 100% seal (because even inner tubes lose air pressure over time) but over a few days or maybe weeks, the pressure will stabilise as the sealant layer builds up.

Try not to worry about it! If the little air loss is not spoiling your rides, then it's a good result.

There are various types of sealant, some thicker, some thinner, some more fibrous some more grainy. It won't benefit you much to change at this point though.

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  • Thanks! What worries me is more the lack of reference points, since it's my first attempt of installing tubeless. But if it's normal, I keep riding. The pressure loss is manageable, I always ride with a pump so can top up if needed. What is better from that point of view, smooth surfaces or going for the roots and the pebbles?
    – Renaud
    Oct 12, 2021 at 19:17
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    @Renaud I’d go for a rougher surface to encourage more tire movement.
    – MaplePanda
    Oct 12, 2021 at 20:02
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    Another excellent reason to go on with tubes!
    – Carel
    Oct 13, 2021 at 7:41
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    @Carel I don't know that I agree with this. On road bikes, I think we're still not yet at the point where tubeless is clearly superior to tubes, and I do run tubes. Off road, which is this poster's application, if you run tubes you take on the risk of pinch flats. Not all tubeless tires keep weeping sealant several days out. This seems unusual, but the tires are still sealing.
    – Weiwen Ng
    Oct 13, 2021 at 14:38
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    @Carel It looks just like a rant against tubeless... but ok. I had my share of tube repairs (thorns or pinch flats). Inflating a tire before a ride (knowing that it won't be permanent) is less of an hassle than repairing a tube in a ride. Especially if the ride is done during a lunch break with meetings afterwards.
    – Renaud
    Oct 13, 2021 at 15:08
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While JoelK's answer is good to keep for reference, the solution here was finally to use another sealant.

After the comments of Nathan Knutson and MaplePanda + an additional 75km of rough gravel and no progress on the "soapy water bubble test", I decided to try remove the sealant and try another one (Schwalbe Doc Blue, which is a rebranded Stan's no tube). The difference was almost directly visible: a 2 km ride was enough to fill pores that were not filled after 100km.

I was using Mavic's sealant, which is only certified for air tight tires (UST or tubeless, not tubeless ready), and is quite viscous compare to Stan's. I would then assume it couldn't go through the pores of the tires. Maybe it would have worked if I kept riding longer, but given I plan a biking holiday in the coming weeks, I didn't want to take that risk. It looks like this reasoning could be extended to latex-free sealants.

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