Tubeless technology has revolutionised (if you'll excuse the pun) mountain bike wheels and tyres. Not only does it reduced weight (by removing the inner tube), using a liquid sealant inside the tyre can actually fix small punctures while you ride. Here's how it works.

Upgrading your bike to tubeless tyres is a win-win decision. Fewer punctures, less weight and better grip are just a few of the potential benefits. But how does it work? Ben Evans from Stan’s, Mark Weir from WTB and Tom Makin from Peaty’s reveal the science behind mountain bike tyre sealant. It’s a bit like vomit or blood?! Okayyy…

Sealant hardens up and dries when it comes into contact with air, right?

Nope, it’s not quite that simple you doofus, otherwise it would just go solid inside the tyre. “Once it does hit the outside air there is some drying of the sealant but I wouldn’t say that is the driving force behind the sealing,” Ben Evans from Paligap, which distributes Stan’s, says. In fact the sealing crystals in its solution clog the hole and they get carried there suspended in the solution.

Tubeless plus sealant

Much like chunks in vomit then?

Actually, yes. “Like when I got food poisoning,” explains Mark Weir from WTB. “As the liquid came out of my throat tube the steak and chicken chunks got stuck in my sinus cavities kinda sealing them.”

The scars of punctures past

Say goodbye to puncture repair kits!

Lovely. Isn’t there a nicer way to think of it?

We could compare it to bleeding, if you like? “Think of it like when you have a cut — blood comes out at first, then congeals and blocks the hole,” says Tom Makin from Peaty’s Tubeless Sealant. “The solution pushes the nano-platelets into the hole, which builds up in layers, so it plugs holes that are over 3mm wide.”

That’s a bit nicer I suppose. Can hardening happen inside the tyre too?

Not really, some drying happens but the trigger for the solidification is the mechanical force of the spray, Mark Weir says. “The spray is strong enough to break the latex droplets allowing isoprene molecules to link to each other forming a solid plug.”

Stans Race Sealant

Sealant should last forever then?

You’re joking aren’t you? All sealants work slightly differently but most are suspended in ammonia, which evaporates over time because the rubber tyre leaches air. Peaty’s says its gunk is different though, water based and so slower to evaporate. “Peaty’s will stay in the tyre pretty much indefinitely,” Tom says.

Any tips for setting up my tyres tubeless?

The most important thing is to shake it up properly, to get the proper distribution of sealant agent to solution.