A tyre boot is a piece of material used in the temporary repair of damage to a bicycle tyre such as a cut to the tyre sidewall. Figure 1 shows a typical sidewall cut. You can see there is a danger that the inner tube will pop through the cut and burst. A tyre boot temporarily covers the cut to prevent the (repaired) inner tube from further damage. The method described here is not suitable for tubeless tyres.
There are a variety of methods and materials that can be used and the following description is but one of them and successfully used by the author.
Material
The material needs to be strong and thin without any sharp edges – strong enough to prevent the inner tube from poking through the cut whilst thin enough to 'wedge' unobtrusively in place, and of course have no sharp or irregular edges to damage the inner tube. Candidates for this include a piece of inner tube cut from a spare, a piece of leather, a £5 note/$1 bill or similar, and so on. In this article I use a piece cut from a toothpaste tube. The tube is plastic on the outer with a thin metallised covering on the inside. Figure 2 shows three pieces cut from one toothpaste tube.
Applying the Tyre Boot
First, replace or repair the punctured inner tube, put a small amount of air in the inner tube and fit back under the tyre leaving one side of the tyre 'unhooked' from the wheel. Take one of the tyre boot strips and place it between the inner tube and the damaged part of the tyre wall, leaving the excess material protruding for the moment. Figure 3 shows this: note the yellow marks on the tyre which are used simply to show the location of the cut.
Fully fit the tyre back into place by easing the tyre bead over the wheel rim, trapping the tyre boot under the wheel rim bead hook and preventing the tyre boot from moving out of place during and after inflation. Figure 4a shows the tyre fully inflated with the metallised side of the tyre boot showing through the tyre wall cut. Using a sharp blade, cut the excess tyre boot away (cut down onto the wheel rim, NOT toward the tyre wall!). The trimmed result (Figure 4b) is a neat finish which at the time of writing has done 60 miles plus with no sign of weakening with the 700c x 25c tyre inflated to 7 Bar / 100 PSI.
Finally, the tyre boot, wrapped around a hobby knife blade weighs about 2gms, costs pennies and fits neatly into the average puncture repair box. To include a tyre boot 'kit' into your repair outfit may well save you or a cycling buddy a long walk home!
Alan Morgan