No More Punctures, Please!
“I have had three punctures on my Brompton since Christmas.The first in the front Marathon, the second in the rear Brompton tyre, prompting me to change it for a Marathon.The third was in the front Marathon again, causing me to regret spending on the rear tyre change. Just to make it worse, Mosquito Bikes fitted a 5/8in (16mm) Schwalbe 4a AV tube that is supposed to stretch to 13/8in (37mm). When it’s stretched that thin, how long will it last?
What BSI tests, if any, apply to kevlar-reinforced tyres? If there are none, what are the closest applicable to motorcycle tyres?”
Mike Hargaden, London
Punctures are a big problem for some people, under some conditions, while others hardly get to see a flat tyre these days. In general, any solution that prevents foreign bodies penetrating the tube (and there are many) will increase rolling resistance, because tough or springy extra layers don’t like to flex, as a tyre must.They obviously increase weight too, and extra weight in the tyre can result in a less sprightly ride and slower response, making the bike feel turgid and heavy. So, even when they work, it’s not all good news.
As for 16-inch (349mm) tyres, the A to B readers’ tyre survey (see A to B 40) suggests that the standard Brompton tyre punctures about every thousand miles, the ‘Green Flash’ kevlar-banded Brompton tyre a little more frequently, and the kevlar-banded Marathon about every 860 miles.This tends to back up my own observations, so taking weight, price and poor rolling resistance into account, I simply wouldn’t recommend kevlar tyres. It may well be that certain types of band perform better than others, but I have yet to see published research on the matter.
Puncture-proof, at a terrible cost, are the so-called ‘solid’ tyres.These may be just tolerable on a 26-inch wheel, but at 16-inch the high rolling resistance and ‘wooden’ feel make these things more trouble than they’re worth.The same goes for ‘solid’ foam inner tubes, about which the less said the better.
Raleigh extra-thick Puncture-Resistant inner tubes provide a good low-tech compromise, but these may no longer be available in small sizes. I fitted a pair to a Brompton two years ago and I’m still waiting for the tyres to deflate. Schwalbe uses a similar technique on its Marathon Plus tyre, which has a 5mm thick flexible india rubber belt under the tread. These tyres are heavy and only produced down to 20- inch (47x406mm), but a 349mm variant should be available soon. I am currently testing a pair of 20-inch examples and will release data in future issues.
Schwalbe Marathon Plus - the thick rubber band prevents penetration
Many proprietory tyre liners are available, but if wrongly fitted these can cause more trouble than they’re worth. As for the tube, Schwalbe does indeed offer a simplified line- up, with typically four or five similar tyres sharing the same tube. However, you should have been offered the 4AV, which is designed to stretch from 28mm to 37mm. I can find no record of the 16mm Schwalbe 4a, which sounds very tiny, and would be quite unsuitable for stretching to 37mm.
Motorcycles do, indeed, puncture less frequently than bicycles, but they also have a lot more power available to roll the tyres, which can thus be made a lot thicker. As minimum horsepower machines, bicycles will always require lightweight and thus vulnerable tyres.
