Stan’s Original was the first Tubeless Sealant I ever used on a UST tyre. As far as I can remember, anyway. Like any sealant, Stan’s can’t seal every hole, especially if you rip rather than pierce the casing or damage a tyre close to the bead or tread block where it is continually getting flexed and pressured. It’s still worked for me repeatedly and quickly on ‘better’ placed holes though, and it’s arguably the best mountain bike tubeless sealant out there.

Cool Original… and still the best sealant out there

Design and specifications

Like many other brands, Stan’s recipe is a closely-guarded secret. Rumours suggest cornmeal plays a part in it, but it’s safe to say it’s a combination of natural rubber latex with various particles and crystals and thickeners to help seal holes fast. There is also an anti-freezing agent in the solution to remain fluid down to temperatures of -20°F (-28°c). God help you if you’re riding in anything below this range.

Stan’s comes in two formulas, Race Day gets more lumpy bits to bung holes, but it’s more money and dries out faster

The US brand offers two blends, Original and Race Day – the latter uses the Original formula but increases the sealing crystal content by 200%. It also adds additional XL-sized crystals to plug even larger holes.

Because it can dry out faster than Original, Stan’s recommends visually inspecting tyres set up with Race Day every 2-3 weeks to monitor liquid levels, but I’ve found it lasts way longer than that in typical UK conditions before starting to dry out. The Original blend is rated for 2-7 months.

Like plenty of other brands’ sealants, Stan’s can cause skin or eye irritation, but I’ve found the consistency and solution to be less messy and gloppy than many and there are also no nasty pieces of glitter or daft base colour to get all over everywhere or your clothes; something that’s often inevitable in the messy business of sealing holes or installing the best mountain bike tyres.

Because the more expensive Race Day formula is so thick, it needs to be poured directly into the tyre rather than installed through the valve, as it can coagulate and block valve cores.

Stan’s is one of the least messy sealants out there, but don’t expect miracles!

Performance

As well as using Stan’s on mountain bikes, I’ve also had the Original Sealant in my road bike tubeless tyres from new. It’s been in there for well over a year and never topped up, but I know it’s still liquid because I recently saw a mist of the stuff coming out of a little hole in the front tyre, where a thorn had gone in. While riding along, the hole was spraying a white Stan’s mist all over my face and glasses for a couple of seconds, but I didn’t even have to stop riding as the tyre only lost about ten psi before sealing. No need to whip out the best MTB mini-pump then.

The incident proves not only how quickly it works, but also that the Sealant hasn’t dried out in over 12 months, despite the bike being ridden mostly when it’s sunny and stored indoors in a warm house.

I change more tyres than your average Kwit Fit mechanic, and Stan’s seems to stay liquid the longest

This mirrors my experience changing mountain bike tyres regularly to test new products. Stan’s stays fluid longer and doesn’t simply coat the interior of the tyre with a layer of latex under centrifugal forces like many others. I’ve returned to multiple tyres over a year later and still found a reassuring puddle, while at the opposite end of the bike another brand’s sealant has evaporated into a rubberised layer with multiple clumps that have zero chance of plugging a leak.

As mentioned, the white milky solution is also not as messy and sticky as other brands either, so it’s much nicer to clean off rims or tyres if it dries on after doing its business out on the trails.

Reserve Fillmore valves make topping up easy

The ultimate formula I’ve settled on is a 50/50 blend of Original and Race Day, which stays fluid for ages and seals really big holes fast. Race Day on its own is a bit too thick and clogs up regular Presta valves over time. Unless, of course, you use the new-school fast-flow valves many brands are now selling like the Santa Cruz Fillmore valves that have a wider core and less bottle-necking at the top.

Stan’s price is higher than many (Race Day especially), but the performance is better too. Because it lasts so long without drying out, I find you don’t have to put nearly as much in as you do with thicker, gloopier blends. You can also manage with slightly less than the brand’s recommendations, which makes it even better value. I usually get to mount around twelve 2.4in or 2.5in MTB tyres out of a 1,000ml bottle.

Sidewall holes are easily plugged by Stan’s Original, provided they’re not too big

You can stick as many screwdrivers into a tyre as you want and watch it seal, but the proof is in the pudding in the real world, where this is simply the most effective and consistent sealant I’ve used. The blend mentioned above has sorted me out even in tyres that are pierced in awkward, harder-to-seal places (like right next to the bead or in the corner of a tread block, rather than on the crown between knobs) and also where changing temperatures and difficult-to-seal holes play havoc with many rival formulas.

Less of this, please