Puncture proof? Well, not exactly. As Schwalbe carefully points out, ‘…like everything in the world – this tyre isn’t indestructible. But against the typical tyre killers that everyday cyclists encounter, like pieces of broken glass, flints and small thorns, it’s the best protection we could devise…’

The secret is in the ‘SmartGuard’ layer under the tread. Unlike kevlar and other high-tech reinforcement bands that resist tyre penetration, SmartGuard is a thick layer of soft rubber that lets them in, then smothers ‘em. Some nasties just bounce straight out, while others begin to penetrate, but are defeated by the sheer depth of rubber. To reach the inner tube, a sharp pointy thing needs to be rigid and 6 – 8mm long, which is enough to see off all but the most humungous thorns, nails and glass shards.

…the Marathon Plus feels like an ordinary, if slightly frumpy tyre…

The downside is a tyre weighing 740g on our 406mm samples (more than a kilogram for some bigger tyres).That’s about 350g heavier than a typical 406mm tyre, and a massive 500g heavier than the lightweight Primos we were replacing. In other words, you could be looking at a weight penalty of up to a kilogram for the pair. With a thick layer of rubber around the tyre, you might expect rolling resistance to be high too, but it’s actually remarkably good. We’ve tried all kinds of ‘puncture-proof’ technology over the years, and most added enough rolling resistance to feel lethargic and slow on the road. But the Marathon Plus feels like an ordinary, if slightly frumpy tyre, and the figures confirm this. Roll-down speed on our test hill was between 14mph and 15mph, which is broadly typical for a 20-inch tyre. In fact, our best figures were right up with the narrow, high-pressure tread- free jobs. Having said that, the Marathon Plus seems to be affected by temperature more than most, and the figures vary a great deal. Most of our tests were carried out at 15C but at 10C, the tyres are 1mph slower, which suggests there could be a real penalty to Grey pay on frosty mornings. blobs are actual We’ll have to wait a few results at around 15C. The months to find out, but in black blobs are at lower temperatures most circumstances, most people would be unaware of the difference.

Puncture-proof?

When we first saw the technology on display at a bike show, Schwalbe was encouraging punters to stick pins in the tyres. So in an A to B first, we put down a row of five drawing pins, accelerated towards them, and ran straight over the lot. All the pins stuck in the front tyre and stayed there, but when we prised them out, the air stayed put. It’s difficult to be scientific with tyres, which are notoriously fickle in the way they fail, but for the time being, we’re thoroughly convinced – no ordinary tyre could have done that.

Grey blobs are actual results at around 15C. The black blobs are at lower temperatures.

Conclusion

…Have we accidentally created the most reliable bicycle in the world?

We’ll keep using the Marathon Plus to see how things progress, but on a short acquaintance, we’re impressed. A near one kilogram weight penalty would not suit a bike that gets carried regularly, but if punctures are your biggest fear, these tyres will give some peace of mind, although at £23.99 each, they’re quite a pricey option.The Marathon Plus is available in all the common sizes, down to 47-406mm (20-inch). Schwalbe is planning to release a 349mm (16-inch) version soon, bringing this sort of puncture technology to compact folding bikes too. Performance gets a bit trickier to predict in the small sizes, but if the 20-inch tyre is anything to go by, performance should not be greatly affected.

Incidentally, we tested the tyres on our ancient Heinzmann- assisted Cresswell (now Pashley) Fold-It, currently giving granny-with-train (don’t ask) some gentle assistance to the shops. Have we accidentally created the most reliable bicycle in the world? Simple rugged steel frame, drum brakes (rear only on our example), puncture-resistant tyres and a bullet-proof SRAM 7-speed hub. The only weak points we can see are the cranks and chain, and if they break, the bike still has a front-mounted Heinzmann motor to get you home… If all else fails, it will fold small enough for the train.

Schwalbe Marathon Plus £23.99 each from good cycle shops. Manufacturer Ralf Bohle GmbH web www.schwalbe.com. UK distributor Bohle UK tel 01743 874496 mail info@bohle.co.uk

A to B 48 – June 2005