By Jim Langley
This week’s tip is the result of an email from my buddy Seth. We’ve actually never met in person but have been email pen pals through our RBR comments section and outside it, too. Seth hails from Tucson and one day when I’m there he’s promised to pace me up Mt. Lemmon. Can’t wait.
The note Seth sent that spurred today’s topic was about his recent crash. Only four miles from home, banking into a turn, a sudden loss of tire pressure made his bike slide out from under him. Seth hit the deck slamming the back of his helmet into the guardrail. But, like any good roadie he was more interested in his bike’s condition than his own.
Said Seth, “My tire simply lost pressure probably from the lack of sealant. It’s fine now and the bike is none the worse from the fall.”
Tubeless Tires and Pressure Loss
Lots of things can cause a tubeless tire like Seth’s to go soft or even almost flat. For me, it happens more often on my mountain bike than on my roadster. That’s because there are more obstacles creating opportunities for what’s called “burping.”
Burping is the tire unseating in one spot, which lets some air out, sometimes a lot of air. The last time it happened to me I had attempted to manual up and over a ledge. In case manual is gibberish to you, here’s a how-to: https://www.pinkbike.com/news/how-to-manual-with-duncan-shaw.html.
When I did it, I cleared the ledge with my front tire but brought the front end down to one side causing me to strike the rear wheel and tire crooked on the ledge, which created a peeling force that unseated and burped the knobby. Suddenly I had a flat. But it wasn’t really a flat, rather a loss of air. Adding air got me back on the trail.
Sealant Doesn’t Last Forever
The role of sealant in tubeless tires is to travel to any air leak and seal it. It can and will do that as long as there’s enough inside the tire.
I used Stan’s No Tubes as a reference here because they’ve been in the tubeless game since the beginning and I’ve used their products since then. They recommend 2 ounces (60ml) of Stan’s sealant for road tubeless tires.
And, for maintaining sealant, they say “The sealant should last an average of 2-6 months depending on factors such as: temperatures and humidity in your area, how often you ride, where you store your bike (cooler is better), tire casing thickness, number of punctures the sealant has already sealed that you never knew you had, etc. A good preventative maintenance schedule for most riders is to check/refresh your sealant quarterly (every three months).”
In order to check your sealant level, you would need to remove enough of a tire to look inside. That means breaking the tubeless bead lock on tubeless-ready rims, which you may not want to do. Because if you only have a floor pump, you might not be able to inflate the tire enough to get it to reseat.
An easier approach is to just assume you need a little more sealant and squirt it into the tire through the valve. To do this it helps to have a valve core removal tool. I like Park Tool’s Valve Core Remover: https://amzn.to/3tBu5tN.
With the tool (or you can carefully do it with pliers – don’t ruin the valve core!), you can hold and turn the tubeless valve’s core counterclockwise to remove it. First, be sure to rotate the wheel so the valve is at about 10 o’clock or else some sealant could come out along with any remaining air that leaks out.
It’s also a good idea to lift the wheel off the ground before removing the valve core. That way the floor/ground can’t push on the tire and unseat it from the bead lock, which is unlikely but might happen.
Dealing with a Clogged Valve
Because sealant’s job is to travel to where the air escapes, it’s likely that it may have created a skin inside the tire over the valve hole. If that’s the case, when you try to squirt sealant in it won’t go in because the skin will block it.
To prevent any chance of this happening, once you’ve removed the valve core, especially if no air comes out, poke something harmless into the valve core to break the skin (nothing pointed because you might puncture the tire). A handy item for this that you probably already have in your shop and that will fit in any seat bag is the applicator tube/straw that comes with cans of spray lube.
Simply poke that into the valve until you feel that there’s nothing blocking the valve hole anymore.
Inserting Fresh Sealant
There are injector tools for putting sealant into valves. But, it’s easy to do it with the nozzle that’s built into Stan’s No Tube’s 2 ounce size of sealant, too. This will fit in a seat pack, too. Once it’s opened, you can push the nozzle into and hold it onto the valve and squeeze the tube of sealant to squirt it all into the tire. If you buy a supply of sealant in larger containers you can keep refilling the 2 ouncer and use it again and again.
Squeeze the sealant in with the valve at about 9 o’clock or 3 o’clock so that the liquid can drop down into the tire. Once it’s in there, screw the valve core back in. Then reinflate the tire.
To ensure the new sealant seeks out and stops any air loss, spin the tire a lot. It also helps to ride around, which flexes the tire casing and helps the sealant seal any pores and gaps that need it.
Hopefully, refreshing your sealant on a regular basis will prevent any sudden tubeless tire pressure loss and especially any crashes from them.
Please share your favorite road tubeless tire sealant tips for preventing these issues as there are lots of choices in sealants, tubeless tires and maintenance tools and techniques.
Jim Langley is RBR’s Technical Editor. A pro mechanic & cycling writer for more than 40 years, he’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Tune in to Jim’s popular YouTube channel for wheel building & bike repair how-to’s. Jim’s also known for his cycling streak that ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.