Wickens & Soderstrom No.8 Tyre Sealant

If you run tubeless tyres, you need sealant. The Wickens & Soderstrom No.8 Sealant is a great choice because it does away with the faff of regular checking to make sure it's not dried out.

The major tyre sealant brands - Stan's, Caffélatex, Schwalbe, Bontrager and so on - are Latex-based. That means they dry out, require topping up, and depending on your riding and location could see you stuck miles from anywhere with a dry, non-sealing tyre. The only real alternative was the non-Latex Slime Pro sealant, but that's not really good at permanently sealing cuts larger than a pinhead.

So a non-Latex, non-drying sealant capable of sealing bigger cuts is the Holy Grail of tubeless. In the No.8 sealant, UK firm Wickens & Soderstrom is pretty much there. It's developed and manufactured in the UK too.

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A plus of the No.8 is that it's designed for inner tubes as well as tubeless tyres. Some road cyclists and many mountainbikers (self included) who don't yet run tubeless swear by Slime tubes. They can be hard to come by in the right sizes and cost quite a bit, so the idea of making your own is appealing.

You get 300ml of No.8 sealant in the bottle, and a handy pull-out applicator tube that fits over Schrader (car) -sized valve bodies to squeeze into the tyre or tube. To aid getting the right amount in the bottle has a handy fill level marking on the side, so you know exactly how much has gone into the tyre. For Presta valves you'll need a Schrader->Presta adaptor, a quid or so from any bikeshop. W&S recommend 50-80ml per tyre, I found a bit more like 125ml worked best to get the tyre seated and maintaining pressure. So each bottle will do you two or three tyres - that may seem like not many, but the key thing here is that the No.8 stays liquid, forever. My test period extended 6 months over a British Summer and Autumn so not technically 'forever', but the sealant looks exactly the same now as it did on Day 1, quite a few thousand miles ago.

I ran the No.8 in a pair of Schwalbe One 28mm tubeless. They sealed up fine - no compressor needed. This is probably more to do with this particular tyre/rim combo leaving the tyre to unfold and warm up etc, but the No.8 helped effect an instant seal.

The Schwalbe One Tubeless is a pretty tough, grippy tyre in its own right and tubeless in general are known for puncture resistance. However they aren't bulletproof, and if/when something does get through you need sealant to stop all the air falling out. If you're using Latex-based sealant you then have to keep an eye on it to ensure it's not dried out, and top it up every few months. This checking/topping up is something you need to remember to do, risking a long walk if you get caught out with a decent bit of flint/glass and dried-up Latex. If you break the bead seal on some tyre/rim combinations to check the sealant level you need a compressor or CO2 cartridge to get it re-seated/sealed, so this is something you really want to avoid doing.

Over the test period I swapped the tyres between three different wheelsets, each time being careful to keep the tyre upright when removing/refitting. Any sealant left on the rim was scooped up and plopped back into the tyre, so it was an almost lossless process.

W&S label the No.8 Sealant as 'Non-hazardous'. It smells innocuous, and isn't unpleasant to work with. In the sealant are larger bits of what looks like particles of rubber, I imagine to fill the larger holes - they claim up to 6mm. Certainly a 3mm hole right in the middle of the tread sealed itself instantly, but what was noticeable over time was a slight weeping - not much at all, but it didn't seal 100%. This is almost certainly down to the higher pressures involved - around 55PSI instead of a much more mountainbike-friendly 20-25. The No.8 started life as a mountainbike sealant and is therefore formulated with lower pressures in mind. Certainly you wouldn't want to be putting much more than 60-65PSI in and expect a permanent puncture seal from a decent cut, so it's more for bigger chamber tyres than race widths and pressures. W&S have a road-specific No.9 sealant under development now, and we look forward to trying it out. I had to top up the tyre pressure maybe once a week - so no more than for a standard butyl tube.

> How to fit a tubeless tyre 

Caffelatex recommend 50ml per tyre, and checking or topping up every two months. At £10 for 250ml, that's arguably £10 worth of sealant per tyre per year, plus four or five sessions checking the level and topping up.

Stan's works out a bit more economical using the recommended amounts, but you still have the Latex conundrum of not knowing how much is left and having to top it up.

So for £18 you can do two or three large road tubeless tyres, and in theory the sealant will last the life of the tyre - possibly longer if you scoop it out and add to a new tyre. The value of not having to faff about checking levels or risk being caught out with a dry tyre is the biggest bonus. If you run more than 55-60PSI you may want to wait for No.9 to come along.

Verdict

A pricey but effective sealant for tubeless tyres - possibly the last bottle of sealant you may ever have to buy.