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Sealant blocking valves on gravel bike

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[#13536433]

Since going tubeless on my gravel bike, I've had an issue with the valves getting blocked. If I leave it for more than a week or two, the valves are usually blocked when I come to check the tyre pressures. Removing the valve core and a wiggle with a cocktail stick sorts it, but it's irritating. I'm using Peaty's tubeless valves and Stan's sealant. I use these with no issue on my mountain bikes. I'm wondering if it's something to do with running higher pressures on my gravel tyres? Should I try different valves and or sealant?


 
Posted : 25/07/2026 1:56 pm
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Remove the core and after cleaning it spray with a liberal amount of silicone spay.

Been doing it for years and never had a problem since.


 
Posted : 25/07/2026 2:08 pm
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When you leave the bike Sat (or hung up) for any period of time, take 5 extra seconds to make sure the valves are sat towards the bottom (6 O’clock position). 

It means that any sealant sat inside the valves has gravity helping it to “drain” back into the tyre. Make sense? 


 
Posted : 25/07/2026 2:09 pm
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Thanks both. I do the 6 O'clock thing but I'll give the silicone spray a try.


 
Posted : 25/07/2026 2:15 pm
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I think this may be a pressure thing.  Although my MTB does gum up, my gravel bike does it more.  

I wonder if the pressure / rush of air through the valve causes some kind of evaporation/hardening effect.  

And @tracey that sounds like a great tip.  


 
Posted : 25/07/2026 2:28 pm
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I fitted some of those 'Corecap' adaptors that basically turn the Presta valve into a glorified Schraeder valve. 

Seem to have been a relatively cheap and easy fix, better flow rate than Presta too which seems to help tubeless seating, or at least doesn't require the valve core to be removed.


 
Posted : 25/07/2026 3:39 pm
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Silicone spray works, better still is a dab of silicone grease which also stops the little Presta nut getting jammed with sealant


 
Posted : 25/07/2026 5:15 pm
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+1 on silicone spay, GT85 works too. 


 
Posted : 25/07/2026 5:26 pm
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I use Stans and, for some reason beyond my fathoming, the Peaty/Chris King tubeless valves suffer from blockages more than any of the others I have.


 
Posted : 25/07/2026 5:35 pm
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I'm running* Stans sealant, Stans valves, Swalbe G1 tyre, generally not had a valve gum up, but the silicone tip is useful to know.

 

*Gravel bike, 35 psi, have to wait overnight with a new tyre for the sealant to find 'micro' holes in the sidewalls and stop the air bleeding. Only possible to find by spraying with soapy water.


 
Posted : 26/07/2026 11:40 am