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I've bought this bike new about 10 months ago. No issues until now, only the fact that my tires (tubeless) lately have constant white foam like this:

enter image description here enter image description here enter image description here

Now I have to pump up my tires every day before I ride, but the bike is still usable through the day even for long rides.

Now I know that I should take it to a shop, but I want to know what to expect there, would it be a difficult and expensive job?

Thanks!

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    it appears to be tire sealant doing its best to seal punctures in the tire. Did you happen to ride the bike while it was under-inflated, perhaps a lot? If so, you may have caused significant damage to the tire. You may be out the cost of a new tire. – Ross May 13 at 21:08
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    I would guess that that is the goo inside the tire oozing out. You have apparently developed multiple holes in the side of the tire. This could be due to having a really cheap tire, or it could be due to some sort of abuse, such as riding with excessively low pressure. – Daniel R Hicks May 13 at 21:08
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    Are these the tires that have been on the bike the whole time, did you just add sealant or has it always been in there as well? Some tires when setting them up tubeless for the first time tend to leak from the sidewalls and "tubeless compatible" tires require a layer of sealant to build up before being completely air tight. This is normal for a lot of tires mounted tubeless for the first time, it is not normal if you have had the tires and the sealant mounted for the entire 10 months. – Nate W May 13 at 22:01
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    @LogicalBranch google 'derailleur gears' – Argenti Apparatus May 14 at 10:33
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    Look carefully at the uppermost sealant leak, there is clearly a serious abrasion to the sidewall. What caused it is unclear, but this is not a 'typical' case of leaking through the sidewalls, it is due to damage. – Andy P May 14 at 10:57
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What you are seeing is likely the result of two issues combined:

  1. Running tires a very low pressures can damage the cords allowing a path for air and sealant to escape (see picture below).
  2. Old sealant can lose its effectiveness meaning the leaks through the broken casing never fully seals.

Damage to the side wall is not ideal, but the tire may still be functional with a sealant refresh. This should be done every few months anyway, depending on the sealant used. If you have never done this, after 10 months you are likely at the far limit of sealant lifetime.

You will need to let the air out, remove the valve core, add sealant, put the valve core back in, then re-inflate. Some people like to remove the tire and clean everything out, which is the best option, but requires you being able to seat a tubeless tire, which can at times be difficult depending on the tire/rim combination and the tools you have available (e.g., external air tank that can be pressurized to deliver a large volume of air to seat the tire).

A thicker latex sealant such as Orange Seal will likely work best to plug the side wall weeping you are experiencing. The tubeless tire pictured below have very weepy sidewalls to begin with, even without cord damage, and the manufacturer recommends Orange as one of the few sealants that will work on this tire.

Sealant leakage However, you also don’t want to run too low a pressure with tubeless tires. If the tire flexes excessively, this will break down the casing until it starts to leak (above).

-- The Trouble with ‘Road Tubeless’

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Modern tubeless bicycle tires require a sealant to be added to the inside of the tire. If a small leak develops the sealant seeps out, meets air, solidifies and seals the leak. I believe this arrangement has become popular because earlier tubeless standards like UST required heavier tires.

The white foam dots you see is the tubeless tire sealant leaking out of holes in the sidewalls of the tire, and failing to seal them completely it seems.

what's fascinating is the pattern of holes in the sidewall, I've never seen anything like that before. I think commenters on on your question are correct, there's possibility you have damaged the sidewall by riding with excessively low pressure which has folded the sidewalls at an acute angle.

Refreshed sealant may solve the problem - sealant loses effectiveness over time. Replacing sealant or a tire is not difficult and is relatively inexpensive, depending on the the replacement tire you choose.

Have the bike repair shop check the tire for damage, if the tire is obviously damaged or even suspect I'd opt to replace it as the labor cost for replacing the tire with new sealant will be the same as replacing sealant in the existing tire.

While you are at the bike repair shop, have the rear wheel checked for trueness , you may have suffered some impacts with the tire under-inflated. Also, think about getting yourself a pump with a pressure gauge to avoid future problems if you have been under-inflating the tire.

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    thanks, from comments here it seems that I should take tire pressure more seriously and stop riding like that. – Claudiu Creanga May 14 at 10:18
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    @ClaudiuCreanga Based on comments and other answers it seems you may not have damaged the tire - some tires just leak like that, but you should maintain tire pressure anyway for a better ride, grip and tire life. – Argenti Apparatus May 14 at 10:39
  • I would disagree with the update. Upon close inspection of the uppermost sealant leak there is clearly a large abrasion. The sidewall has either been damaged by riding at much too low pressure or by sabotage. – Andy P May 14 at 10:54
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This is an issue that often happens when you combine a tyre that doesn't hold air well with a very light sealant. The solution is to add in a sealant that's a bit thicker and chunkier. A mix of 50% NeverFlat and 50% Stan's works very well.

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    Have you seen sealant coming through the sidewalls like that on other tires? – Argenti Apparatus May 14 at 2:17
  • I see it pretty regularly. Mitas tyres are the worst offenders. – Carbon side up May 14 at 10:08
  • @ArgentiApparatus Not to the extent as seen in OP, but (even brand new) Schwalbe's tend to seep at the sidewalls, especially if you go with the Liteskin models. – Kenneth K. May 14 at 14:43

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