As regular readers will know, punctures and/or poor rolling resistance come up all too frequently on these pages – for the latest technical meanderings, see page 17. As a general rule, anything that serves to reduce rolling resistance will make a tyre more prone to punctures and vice versa.The greater part of rolling resistance – at low speeds, anyway – is the result of unwilling tyres and tubes flexing against an unforgiving road, and there’s no escape from that.
A thin inner-tube will roll well but tend to puncture, whereas a thick tube (or a thin tube plus a tough liner) will roll badly, but resist punctures. Clever technology can help in either case, but this month we’re looking at a product from the ‘brute-force’ end of the technology spectrum – Raleigh puncture-resistant tubes. We’ve chosen a 16-inch example, because rolling resistance problems are always amplified with smaller tyres.
The principle is simple enough – the tube is made of fairly conventional stuff, except on the top face, which is thick enough to prevent most objects penetrating to the air reservoir inside.The first disadvantage is a weight per tube of 260g, giving a weight penalty against conventional tubes of about 70-100g per wheel, or 140-200g for the pair. Quite a lot, but rather less than Schwalbes’ new puncture-resistant tyres (see page 20).
The other disadvantage is poor rolling resistance. Brompton’s 349mm tyre is usually one of the best in its class, and with conventional tubes, and typical tyre pressures of 55psi (front) and 65psi (rear), we recorded a typical 14.3mph on our test hill.
Fitting is no more difficult than usual, although it’s best to avoid ‘rolling’ the tube in, because if it twists, the thinner underbelly may end up on the top. Once fitted, and back at 55-65psi, we recorded a rather miserable 11.7mph, although inflation to 90psi all round brought this back up to 12.7mph, albeit with a fairly rough ride. If the figures mean nothing, it’s rather like swapping 16-inch tyres for 12-inch examples, or going back twenty years, when most 16-inch tyres performed this way.
Whether you think the extra weight, 11% -18% loss of performance, and rough ride are worth all the trouble depends on your fear of punctures, and just how effective puncture-resistant tubes really are, which we can’t tell you.
Puncture-resistant tubes are available in most popular sizes from 121/2 inch upwards, but Raleigh tell us the 16-inch tube tested here has just been deleted, due to lack of demand. Stocks may still be available, particularly in the smaller, friendlier sort of cycle shop. And the tubes are made by our old friends Cheng Shin in Taiwan, so there might be an opening here for a budding entrepreneur.
Raleigh Puncture-Resistant Tubes (all figures relate to 16-inch tube)
Price £5-£6
Weight 260g
UK Distributor Raleigh Parts & Accessories Tel 01623 688383
