Fenwick’s Airtight is a non-latex-based tyre sealant that can be used in tubeless tyres to protect against punctures up to 6mm in diameter, provided that the tyre’s treads are not wrecked.
It can also be used to convert non-tubeless tyres to tubeless, works in sub-zero conditions and gives a permanent repair to any punctures it encounters. Or so Fenwick’s claim. Yep, we thought that sounded like mere marketing spiel too, until we tried it…
Our first test was on tubeless tyres, where we simply poured 50ml through the valve and rotated the wheel for a while after inflating to disperse the sealant. We encountered no leaks, so we punctured the tyre. It took 28 seconds to seal, but major air loss was drastically reduced after just three. The 3mm hole caused a reduction in pressure of 18psi (from 110psi), and aside from normal slight pressure loss it hasn’t deflated any more since.
For our second test we converted a regular tyre into a tubeless tyre by painting a layer of Airtight onto the inside of the tyre and the bead. The result was a tyre that was easy to fit and to inflate, kept its pressure, and made next to no mess at all (the initial job of painting it on was a bit messy, but hardly anything seeped out). In our puncture test it did lose just under 30psi, but it sealed securely.
For our final test we put 25ml (half the recommended amount) into an inner tube in a normal clincher tyre and tube setup, and our 3mm hole was completely sealed almost instantly. Concerned this could be a one-off, we repeated the test and sure enough it did it again, and again.
So what we thought were perhaps over-inflated (sorry!) claims about the product’s performance turn out to be quite true. You could say that Fenwick’s Airtight actually does more than it says on the tin (or cardboard box).
The Airtight kit contains a 500ml bottle, which is enough for 10 road tyres, plus measuring scoop, brush, applicator tube and valve kit. It’s also available in a 250ml bottle (£9.99), with 1L refills costing £24.99.