For the Tour of Flanders this Spring I obtained - not without difficulty - a pair of Schwalbe S-Ones, made for Paris Roubaix and the Tour of Flanders. They are racing tyres, made to race on the cobbles, and only come in 30mm. They are light, flexible and tubeless, and performed impeccably. Good grip and no punctures, at improbably low pressures.
For some reason I can't put my finger on, I later put these on my Lynskey Sportive. Just to see how they went, I suppose, but the result was quite surprising. They seemed to roll just as well as the 25mms they replaced, and the Hill of Truth, Root Hill, confirmed that this was indeed correct when I did some roll-out tests.
There are quite a few articles around supporting bigger tyres just now - Richard Hallett had a piece in Cycle a couple of months ago, for example. The argument goes that a bigger tyre will roll better, as long as it is light and flexible.
How so? Well, here's my understanding of it. The lowest rolling resistance is obtained with a steel wheel rolling on a hard flat surface. This is because the wheel is truly round, and has the least impediment to its forward motion. Over the last couple of centuries the railway companies have put a fair bit of effort into systems based on this, and it seems to work well enough.
Dunlop's pneumatic tyre of 1896 takes a different course. The slight flexibility of the tyre allows it to deform as it encounters an obstacle. The energy stored by the deflection is released again as the obstacle is passed, allowing the tyre to roll quite freely on a surface that is only fairly smooth, like a tarmac or gravel road.
This tyre was a great success, and cyclists (for they were the first) quickly realised that you wouldn't win a race if you didn't have them.
If all this is right - and I think it is - then what's the sense in having bicycle tyres that are as hard as possible, which minimises deflection? The very hard, and very round tyre will roll better on a smooth surface, like a velodrome, but in every other circumstance a softer, more flexible tyre should do better.
So I bought a set of 40mm tyres, soft, light and flexible ones, and put them on a cyclocross bike, which was the only one that has enough clearance.
I set these at 55 psi, which seemed to me improbably low, though they will accept much lower pressures, and took the bike out for last Wednesday's A Group ride. This gave the chance to try a few informal roll-out tests with other Wayfarers. The results were quite surprising, and quite counter-intuitive. The bike, which is no racer and not particularly lightweight, simply rolled away from the others. There seemed no loss on climbing, and it was particularly comfortable to ride, as the large, soft tyres masked the rubbish road surfaces we endure.
Now this isn't science, and there's not much rigour in it. But it's firmly rooted in the real world, and it's certainly worth thinking about. There must be limiting cases, but they're more than 40mm, that's for sure.
As with so much in cycling, the wheel gets re-invented (ha ha). Bicycles of this type have existed for a long time, and worked very well. What happened to them? They became unfashionable, I think, as the racers didn't use them. Take a look at these two:
If you could swap the wheels on my Condor so that it had deep tyres instead of deep rims, then you'd have pretty much the same thing. There is progress, of course - indexed gears and the possibility of tubeless tyres. In fact you can't easily make the change, as the frame is too tight, but it's something to ponder over the winter.
Another thing to note is that 'Adventure Bikes' are suddenly on trend. They always have fat tyres ... Funny old world, eh?
Mark
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