Strength of carbon

I enjoyed the article (Feb/Mar issue) comparing Ribble and Hewitt carbon road bikes. I am a 17-stone rider who enjoys 30-plus mile rides a few times a week. I am considering buying a carbon fibre framed bike but have reservations about the strength of carbon fibre, particularly the strength of fork. I would appreciate your comments on my reservations concerning my weight before making a purchase.

David Aylett

Anything is strong enough if you use enough of it in the right way, and in the case of carbon fibres you don’t have to use a whole lot. But the way of using them is crucial and there’s my problem.

From the outside of a ‘carbon’ frame or fork it’s impossible to tell anything about how those fibres are disposed within the plastic matrix. Unlike metal, where fitness for purpose may be inferred from the alloy specification, tube diameters and wall thickness (known or guessed from weight), a carbon component must be taken entirely on trust, and all we ‘outsiders’ can do is observe the pattern of success or failure.

In the early days of carbon forks and frames, there were quite a few failures, but we seem to be beyond the learning stage now. You must nevertheless accept that sports equipment – regardless of what it’s made from – is made for performance rather than long-term durability, so it WILL fail sooner or later: sooner if you’re heavier than average, but later if you ride less than average. Let the manufacturer’s warranty be your guide – it’s all there is to go on. I rather like the fact that Cannondale give a lifetime warranty
– or they did last time I checked.

Some manufacturers specifically exclude use by riders of more than a certain weight, so do check those warranty conditions.

Chris Juden


This was first published in the June / July 2014 edition of CTC's Cycle magazine.