CST Tubeless Tyre Sealant

I've been using CST Tubeless Tyre Sealant for an extended test period, and it has been working well, plugging smaller holes quickly and showing no signs of drying out even with the very hot weather we've had. And though it hasn't lived up to the big 7mm holes claim, it does come very close.

Most tubeless sealants are claimed as being able to fix holes from around 3mm up to 5mm, but CST reckons its offering can seal up to 7mm diameter holes.

To test this, I pierced one of my gravel tyres with the point of a flat wood 32mm drill bit, leaving a hole of around 2mm in width and 6.5mm in length to see just how good the CST sealant was at dealing with what would be quite a severe gash out on the trails. It didn't fully seal it, though it did give it a very good go.

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The 40mm tyre was pumped to 40psi before piercing, and the sealant started to block the hole quickly, with very little in the way of pressure loss. Although it didn't seal the hole completely, it did slow down air loss, allowing me to keep riding for about 20 minutes before the tyre was flat. This might give you enough time to get home, or at least get somewhere flat or dry away from the road or track to fix it.

On smaller, more typical holes you'd get from glass, thorns, sharp stones and the like, I found the CST sealant to be very good. Installation is simple, too, thanks to the nozzle easily fitting inside the valve core, so you don't end up with any mess.

Using an old tubeless road tyre that had previously been fitted with an inner tube, I was amazed at how many small nicks and cuts were on it. The sealant quickly showed itself and sealed all of these small holes – and they have remained sealed even after a few hundred miles.

It copes well with higher road pressures without blowing out, too.

We've had some very hot conditions during the test period, and after a couple of months of use, removing the tyre showed the sealant to still be very much a liquid, with no sign of any of it 'balling' in certain areas of the tyre.

CST recommends topping it up every six months, or three months if you live in hot climes.

> 9 things they don’t tell you about tubeless tyres

At £10 for 250ml (£4 per 100ml) it's not priced too badly; it's a cheaper option than Muc-Off's No Puncture Hassle sealant at £8.99 for a 140ml sachet (£6.42 per 100ml).

The Hutchinson Protectair Max sealant is £6.95 for 120ml (£5.79 per 100ml), while Juice Lubes offers its tubeless sealant at £5.99 for 140ml (£4.27 per 100ml).

When it comes to quantities used, that ranges from 30-50ml for up to a 32mm road tyre, 50-80ml for a 700C gravel tyre, up to 140ml for a downhill mountain bike tyre, so for most of us roadies you're going to be looking at around five tyres' worth of sealant.

Conclusion

Overall, although I couldn't quite get the largest hole to seal, the CST made a pretty good effort, and for the more typically sized punctures you are likely to pick up I'd say it's a sealant you can rely on.

Verdict

Works on the majority of holes, and though it doesn't quite hit its claims it’s still impressive