Let’s get this out of the way first: on the flat, weight isn’t all that important. It might be borderline blasphemy against the Gods of carbon but actually, until the gradient starts to ramp up, the power savings you get from being light simply aren’t enough to warrant the amount of money you’d have to spend to get them.
In his excellent book, Faster: the science of triathlon speed, Jim Gourley shows that the wattage difference between the same 68kg rider on a 6.8kg bike and a 5.3kg bike is barely noticeable until the gradient hits 10 per cent. In fact, it’s about ten watts.
The best way, of course, to reduce your power requirement for going uphill is to reduce your own body weight and/or improve the number of watts you can sustain – your power to weight ratio – and on the flat, weight is nowhere near as important as aerodynamics. Basically, on the flat it’s far smarter to get out of the air’s way than to try and overpower it (and we’ll come on to aerodynamics later).
The reason that you can notice the difference with a lighter set of wheels on the bike is in acceleration – and a bike that accelerates quickly feels good. When climbing at a constant speed, weight is weight, and, by and large, there are gains to be made whether it’s in the wheels, the frame or wherever, but when you’re accelerating, more weight in the wheels equates to more effort to get the bike up to speed. This is especially true if there’s undue weight in the rims, rather than the hub.
So if you’re climbing a lot and want to reduce the weight you have to haul uphill or you want to add some zip to your ride – and especially if, like me, you’re someone who tends to get out of the saddle quite a lot and vary speed, then a light wheelset with very light rims would be a good purchase. One in particular that fits this bill very well is Shimano’s Dura-Ace C24 wheelset (£799.99). At a claimed 1,387g per pair they’re extremely light for the price, and come with the quality you’d expect from something with Dura-Ace written on the side.