Is a lightweight bike worth the extra expense?

Does owning a lightweight carbon fibre bike cut down your commuting time? Contrary to expectations, a trial carried out by anaesthetist Dr Jeremy Groves from the Chesterfield Royal Hospital in the UK suggests that cyclists should pay more attention to the weight of the rider than the bike!

Writing in the 2010 Christmas edition of the British Medical Journal, the author documents a comparison between the time taken to complete a 43.5 kilometre commute to work using either an older, secondhand steel-framed bicycle bought for £50 and weighing in at  13.5kg, or a new £1000, lightweight 9.5kg carbon-fibre model purchased thanks to a "cycle to work" tax incentive scheme.

Groves compared his performance on each bike over a six month period, determining which bike to use on each day with the toss of a coin. Ultimately, thirty commutes were made on the steel-framed bike and 26 trips on the carbon fibre machine. The journey times were logged with a cycling computer, which  clocked up 1144 kilometres over the course of the study.

Surprisingly, despite costing twenty times the price and weighing thirty per cent less, the carbon fibre bike was no faster than the steel-framed model. The top speed achieved - fifty-eight kilometres per hour - was the same on both bikes, and the average journey times were 1h48m21s and 1h47m48s respectively, although times were longer in the winter (owing to winds, heavier clothing and more cautious cycling on the part of the rider). Moreover, the author reports that the ride afforded by the carbon fibre bike was much less comfortable and the fear of falling off is higher in bad weather, leading to longer journeys.

Most importantly, Groves points out that although the thirty per cent reduction in bicycle weight achieved with a carbon-fibre frame sounds like a lot, this difference narrows to just 4% when the combined mass of the  bike and rider is considered.

"A new lightweight bicycle may have many attractions, but if the bicycle is used to commute, a reduction in the weight of the cyclist rather than that of the bicycle may deliver greater benefit and at reduced cost."