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Not really asking for advice as such, just curious if anyone has ever definitively found out what happens sometimes.
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Last night I ended our night ride on an increasingly squirmy rear tyre. Whilst we were having the post-ride pint the tyre went down fully. Unwisely, on getting home I had a go at blasting a load of air in and shoving a tyre worm in, but no dice.
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So, this evening, I go to fix the issue thinking it is going to be a full re-taping job. But, on pulling off one side of the tyre, all I see is a set, graphite grey slick all around the middle of the tyre interior. Rim strip still in place, tape perfect. So I pour some sealant in, re-inflate and it is fine again.
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The tyre is a Shorty (my winter tyre) and was installed at some point probably early November.
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This issue with sealant going 'off' has happened to me once before. But it was summer and I just assumed it had dried out due to temperature.
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Has anyone else had this and, more importantly, does anyone know what causes it?
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I'm asking out of curiosity more than anything else.
I've had the same, and got fed up of cleaning the congealed leftovers out of tyres (or rather not bothering to) so I just switched to Peatys instead.
I think it's because it takes on water/moisture over time? They state it needs replacing every 2-7 months I assume for the same reason.
Any CO2 used? I've had Stans in my tyres for months (prob up to a year) and had no great issues. It needs a bit of a top up now and again and when I swap tyres I'll have a clean up of anything that's hardened but otherwise it's pretty low maintenance. Â
The only thing I do notice is that it really doesn't like CO2. Not sure if it's chemical or the coldness.Â
Nope, not used any CO2.
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I've only ever used Stan's. Is Peaty's any good and what is the comparable cost per 100ml?
Yeah, it dries out over time and it's pretty hard to predict how fast- I think some more porous tyres let it happen faster, temperature seems to make a difference (I keep my bikes in the house, it was a problem). But sometimes it lasts ages and sometimes it doesn't.
(this will seem like I am trying to get you to join a cult but) OKO Hi-Fibre gets around this, it's water based and water soluble so if it's drying up you can just add water to redilute it. You can't do it once it's dried out completely, it has to still be wet, so it's not a miracle cure but it means you can keep one sealant fill going basically forever. (or dilute the fairly thick sealant to taste, I think it's a little thick as it comes) As far as I can tell it works about as well as Stans Race, but tbh who can really say, punctures are a bit random. But it definitely works well enough to not stress about how well it works.
It's also very cheap! But the downside is it's not available everywhere, whereas Stans pretty much is, and it's incompatible with Stans and some other sealants. So if you ever need a top up when you're out and about that could be an issue. It's the exact same product as Halo sealant and Uberbike, so the odds are getting better, but they're not in every shop either
I got fed up of Stans forming big alien blobs and drying out. Switched to Orange Endurance and have no regrets!
My guess is that it is a latex emulsion with suspended particles.
The latex emulsion will go off if the pH changes dramatically. We used to add ammonium hydroxide to paint to keep it high and stable. That is the assumption on why Co2 is a problem.
It will also require emulsifiers and dispersing agents. The dispersing agents may also accumulate on the tyre becoming less effective on the stans itself.
Then you've got drying out/loss of water when you get small holes and reinflate.
Also just sitting around will cause it to settle.
There may be contaminants in there?
This is what was left of my sealant when I slashed a tyre at Gisburn 😆 
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As far as i`m aware all sealant dries out over time. how quickly depends on the air tightness of teh sidewalls.Â
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