Forty years ago, Doctor Moulton demonstrated that 16-inch tyres offered lower rolling resistance than anyone thought. Controversially, he went on to prove that his own 17- inch tyre rolled as well (or even better) than its 27-inch equivalent. For many years, the ‘cooking’ Moultons were sold with smaller 16-inch tyres, or to be more precise, 16″ x 13/8″. Incidentally, there are three slightly different 16-inch formats, so its safer to use the international metric rim size: 349mm. Look on the tyre and you’ll usually see 37-349.The 37 refers to the width in millimetres (that’s the 13/8″ bit).

While sales of the Moulton were strong, these tyres became widely available, but with the decline in Moulton sales at the end of the 1960s, tyre companies lost interest, and the 349mm format began to fade away.

Fortunately, as we’ve recounted numerous times, this ‘ideal’ folding bike tyre size was saved – initially by the Bickerton (fitted only at the rear, of course), then the Micro, and from the late 1980s, the Brompton and later the Airframe. It might have been an ideal size, but by this time there was only one half-decent tyre left in mass production – the Raleigh Record.

In 1996, with the arrival of the race-bred Primo Comet, 349mm tyres were back at the cutting edge.The better tyres helped to sell bikes, and more bikes brought better tyres…There are now four main choices, and a number of interesting developments on the horizon.

Most of these tyres are available with or without a tough kevlar under-layer to resist punctures. Kevlar increases rolling resistance, but we’re not convinced it reduced punctures.The results of our small reader’s survey (sent out with December 2003 renewals) seems to confirm this.

Raleigh Record (37-349mm)

Are we serious? Well, they’re cheap, but thereafter it’s all negatives: the Record is heavier than the new breed, it punctures more frequently, rolls less well and is more difficult to remove from the rim. For very mean people who don’t mind mending a few punctures, a pair of Records will last 3,000-4,000 miles. But life’s too short, surely?

Points to watch: Prone to punctures, particularly when badly worn, but may outlive you.
Weight: 338g
Puncture resistance: Mediocre
Rolling resistance: Poor
Price: £5
Outlets: Less glamourous cycle shops

Primo Comet (37-349mm)

The story has it that American recumbent manufacturer Vision developed a small race- bred tyre, and licensed the technology to Cheng Shin in Taiwan, who succeeded in producing an everyday racing tyre for an everyday road price.The magic ingredients were a near-slick tread, and strong, but paper-thin reinforced sidewalls that rolled and flexed much better than the conventional kind, yet lasted almost as long.What also impressed about the Primo was its strikingly low weight of 201g a tyre – a saving of no less than 137g over a Raleigh Record. As if by magic, small wheeled bikes started to go much, much faster, and weigh less too. Strangely enough, considering the Primo’s light, supple construction, the tyres proved to be relatively puncture-proof, and (on tarmac, at least) the lack of tread has no negative effects. Needless to say, this is not a tyre for muddy or loose surfaces, and the sidewalls will be damaged if used with a dynamo, but the Primo remains a firm favourite with some.They’re surprisingly hard wearing too. With care (ie, no dynamo and no riding whilst flat), a Primo should last up to 3,000 miles and puncture around every 1,000. Eventually, the sidewalls become a bit frail, and cuts in the tread harbour glass and flint shards, causing more regular punctures.

Early Primo tyres had natural brown sidewalls that soon looked shabby, but later examples were all-black, and some have reflective sidewalls too.There’s a kevlar option, but we’ve seen no evidence that it’s worth paying extra for.

Points to watch: Rolling resistance is so low that you may not notice a puncture before the rim hits the ground. And avoid the ultra-light 19mm (19-349) Primo unless you’re building a one-race special. Although light and free-running, it is unsuitable for road use and can fail rapidly.
Weight: 201g
Puncture resistance: Good
Rolling resistance: Excellent
Price: £15
Outlets: Rarer now, but try Avon Valley Cyclery or St John Street Cycles (see ads in back pages).

Brompton (yellow flash) (37-349mm)

By the late 1990s so many Brompton customers were fitting their own Primo tyres that Brompton decided to develop a road version for themselves. After a number of experiments, the now familiar ‘snakeskin’ tread pattern first appeared in early 2000 and was soon standard on all Brompton models, apart from the lowly C3.

With thin supple Primo-style sidewalls, and a tougher, but equally flexible (possibly more flexible) tread, the tyre was expected to have slightly inferior rolling performance to its racing forebear, but our tests found little difference, and engineers at Greenspeed (see graph) have actually recorded a modest improvement.This may be down to the rubber compound chosen – the Brompton tyre is quite hard, making it relatively puncture resistant and very long lasting. According to our reader’s survey, Brompton tyres have a life of 1,000 to 8,000 miles, with a mean figure of about 4,000 miles; something we’d agree with from experience. Puncture resistance seems to vary a great deal, but the mean figure is 1,060 miles – far in excess of any other tyre. Indeed, almost half our respondents had never experienced a puncture.The downside appears to be a lack of grip in the wet, particularly when running obliquely to white lines and low kerbs. The evidence for this is quite patchy, but sufficiently widespread to cause concern.

If the standard Brompton tyre is so good, surely the ‘green flash’ kevlar-lined version is even better? We don’t think it is. Our reader’s sample was small, but together with the evidence we’ve seen over the years, it suggests the kevlar tyre has a shorter life and is actually more vulnerable to punctures.

Points to watch: May lack grip in wet weather, particularly when new. Either ‘run in’ with care for a few weeks, or try buffing the tread with sandpaper before use!
Weight: 248g
Puncture resistance: Excellent
Rolling resistance: Excellent
Typical Price: £9.99 (kevlar ‘green flash’ tyre, about £16.25)
Stockists: All Brompton dealers

Schwalbe Marathon (37-349mm)

The Marathon is a newish tyre, allegedly developed from the long-established Swallow, which sold here back in the days when the Brits were a bit suspicious of the Germans and preferred to buy products with British-sounding names. Still, we’re all friends now, eh?

This is the only modern 16-inch tyre relying on ‘old-fashioned’ tyre construction, but the Marathon incorporates plenty of clever technology, including rubber with a high silica content to improve grip and a kevlar belt for puncture resistance.

The general consensus is that the Schwalbe is relatively puncture-proof compared to the lighter tyres, but our reader’s experiences seem to tell a different story.Your figures suggest average tyre life in the region of 2,300 miles, and punctures every 860 miles.There are many reasons why our results might not be scientific – for example, a tougher looking tyre is more likely to be fitted to a hard-ridden machine – but the evidence appears to suggest that they have a shorter service life and more punctures than their lighter (and cheaper) cousins.They can also be a tight fit on the rim, making punctures even more annoying. And according to the Greenspeed data (see graph), rolling resistance is rather higher – the Schwalbe absorbing as much as ten watts more per tyre than the Brompton. At18mph (the speed at which the tyres were tested) that relates to around 16% extra effort.Whatever the truth (and Greenspeed believes its test methods may exaggerate the differential) the Marathon is a safe, grippy tyre that looks effective, and it has rightly settled down as a popular option. For tough conditions and off-road use, it is probably the best choice.

The seriously puncture-proof Marathon Plus should also be available in this size soon, but Bohle UK was unable to confirm a date.

Points to watch: Vice-free, but stodgy performer
Weight: 340g
Puncture resistance: Good
Rolling resistance: Fair
Typical Price: £15
Stockists: Most small-wheeled bike dealers (see advertisements)

Schwalbe Stelvio (28-349mm)

The Stelvio is considerably narrower than the 37mm tyres, but as it retains the same ‘aspect ratio’ (ie, ratio of width to height), it also has a smaller overall diameter.The tyre will stretch to fit the 20mm rims fitted to the Brompton and most other 16-inch bikes these days, but the reduced tyre diameter means you’ll have to recalibrate your speedometer, and accept slightly lower gearing.

The tyres feature just about every technology going – the sidewalls are paper thin, Primo- style, the centre of the tread is a slick, low-friction rubber, and the shoulders a grippy silica mix. Overall weight is marginally the lightest on the market at 196g.

Are they worth the money and the trouble? Being such a small tyre, the Stelvio is vulnerable to incorrect tyre pressures – Schwalbe recommends 85psi – 120psi, figures that most tyre pumps simply can’t reach. If run at too low a pressure, the tubes are liable to suffer from pinch punctures on bumps. Punctures do seem to be a problem generally, but there simply isn’t enough evidence to say for sure.

On a Brompton or Micro, the Stelvio serves only to give a spine-jarring ride and over-light steering for no detectable benefit, but this light, fast 120psi tyre might make sense on a fully-suspended bike such as the Moulton – preferably with the correct narrow rims. Provided you look after the tyres, and fit them to the right sort of machine, they may be the fastest 16-inch option.

Points to watch: Some potential for faster machines
Weight: 196g (you can save a further 9g per tyre by fitting Schwalbe 32mm inner tubes)
Puncture resistance: Poor
Rolling resistance: Excellent
Price: £13.50 (including UK postage)
Stockist: Westcountry Recumbents [rob@wrhpv.com]

Conclusion

If weight really matters, the Primo still has much to offer, although you’d be well advised to stock up while they’re still widely available. For racing, it’s probably fair to say that the Schwalbe Stelvio is the best, although we’d hesitate to recommend it for road use.The overall winner, in terms of value for money, life, puncture resistance and rolling resistance, just has to be the standard Brompton tyre.The only question mark seems to be wet weather grip – in all other respects, this is a remarkable tyre.

Incidentally, the tyres tested above are rated at all sorts of pressures, but please ignore such phrases as ‘inflate to 100psi’ (Brompton, in this example).Whatever the graph might seem to indicate, these figures are maximum pressures, and will only give the results indicated on a perfectly smooth surface. For most riders, on typical road surfaces, a lower pressure will give both lower rolling resistance and greater comfort.

A good general guide is to sit on the bike and adjust the tyre pressures front and rear until the tyre just begins to bulge out above the road contact patch.That pressure (always higher for the rear tyre, of course) might be 100psi, 80, 60 or even less, but it will be close to ideal for you, your bicycle and your tyres. On the road, high frequency vibration means too much pressure, and a ‘wallowing’ ride, too little. If this all sounds like hard work, aim for about 65psi front and 75psi at the rear.