Stan's NoTubes Race Sealant seals bigger punctures much more quickly than the regular Stan's sealant. The improved performance does come with a high price tag, but I think it's a price worth paying for the reduced risk of flatting.
Tubeless tyres mean fewer punctures and we are now seeing many manufacturers speccing new bikes with tubeless rims, and often tubeless tyres, as standard. In place of an inner tube, a liquid sealant is used which seals small holes, the sort caused by flint or shards of glass, so you can spend more time riding and less in the gutter getting your hands dirty changing the inner tube.
There are many sealants available, but without a doubt the most popular is Stan's NoTubes Sealant. This year, to mark its 15th anniversary, the company has released this new Race Sealant. It has actually been in development and in use by some mountain bike race teams for the past couple of seasons, and it's now available to us mere mortals. The new Race Sealant uses the same latex formula as the regular NoTubes sealant, but more crystals are added to the mix along with larger crystals. It's designed to be able to seal larger punctures and to seal them faster – the regular sealant works well on small holes but struggles with bigger gashes.
Installing the new Race Sealant is a bit more troublesome because the company advises against piping it through the valve stem because it will clog. Even if you have removable inner tube cores, the lack of a pointy cap on the bottle means the only way to add the sealant to the tyre is to do it directly to the tyre before final mounting of the bead onto the rim.
The first thing I noticed when using the Race Sealant was that the tyre was easier to seal up, with less air leaking from the beads that can sometimes occur when installing tubeless tyres. Next, I inflated the tyres and then took a sharp pointy device and stabbed the tyre, before spinning the wheel to see how well the sealant would cope. There was some air loss, but the sealant did appear to deal with the bigger holes and sealed them up very rapidly. I repeated the process a couple of times and, sure enough, the tyre sealed extremely quickly. Afterwards, I measured the tyre pressure and the drop was perfectly acceptable, the sort of amount that wouldn't prevent you comfortably carrying on with your ride.
Having witnessed tubeless tyres with big holes or slices to the carcass struggling to seal, and sealant escaping at a rapid rate, I was impressed with the Race Sealant's performance.
This isn't the most scientific test in the world, I'll admit. There are many variables when it comes to punctures, and although tubeless setups are great at dealing with many causes of flat tyres, I know from personal experience that they're not 100 per cent impervious to all punctures. The new Race Sealant is an improvement on the regular sealant, with less leakage during installation, and it is better able to quickly deal with a range of holes, up to and larger than those the regular sealant can deal with. Another benefit of the new Race Sealant is that you can use less of it, and so save a bit of weight. The downside is that at £32 for a 946ml bottle, it's £8 more expensive than the regular sealant. For its benefits and superior performance, though, I won't be going back to the regular sealant in a hurry.