“I’m old school and I believe that many cyclists still seek a bike that’s made to last. I continue to believe that being durable is a positively good thing!” (Andy Blance, co-founder of Thorn Cycles)

The Thorn Audax is a nippy bike. It is remarkably lightweight for steel (approximately 10.9 kg) and has a gear range which makes any high gradient ascent conquerable while allowing for fun cruise speeds on lower gradients and descents – as such, this is a touring bike which feels like a racing bike. On its inaugural ride (Chris’s Spin), it was tested up some of the most challenging ascents – Mam Nick and Monsal Head – and descents in the Peak District and managed superbly (with the help of course of its anaemic rider!) This is a highly versatile bike for rides into the hilly countryside, which is precisely what I bought it for. I was looking for something a little lighter and a little faster than the Ridgeback, and the Thorn Audax excels on both counts.

And then there’s the whole Thorn experience! Thorn is a bespoke touring bike manufacturer based in Somerset. I ordered this bike via telephone and email. The detail requested and the attention paid by the folks down at Thorn was exceptional: what they delivered (literally in a box!) was a high-quality, perfectly fitted bicycle that translates into a majestical first-class riding experience. Very important to me is Thorn’s approach to cycling and bicycle production, its ethos, which is commendable. I’ll end this review with the following two extracts – “Steel is real!” and “Does weight matter?” – from the Thorn Mega Brochure:

I. Steel is real!

[…] If you race, you need a racing bike and, if you’re any good – not only will someone buy it for you – they’ll also pay you to ride it! If you don’t race, why on earth would you want a racing bike? Would you buy a twitchy and demanding track day car, such as a Caterham, as an everyday vehicle? It rains in the UK – why would you be prepared to suffer a wet bum and tolerate tyres which puncture easily – or do you stick to smooth but busy, “A” roads? […] In my opinion, high quality steel is the best possible material for a strong, comfortable, well equipped, and long lasting frame. […] All Thorn frames use high quality, heat-treated steel. I wouldn’t wish to build our bikes with anything else and I don’t want anything else for my own bikes! The final heat treatment process can double the cost of a steel cycle tube. Heat treatment raises the UTS (ultimate tensile strength) significantly – this makes the tubes stronger and more resistant to cracking. Heat treatment also makes the tubes more resistant to denting and greatly enhances the frame’s resilience. Resilience can be defined technically as, the ability of a material to absorb energy when it’s deformed and then release that energy upon unloading. In a high quality bicycle frame, it manifests itself to the cyclist as a tight, springy sensation. […]

OTHER MODERN FRAME MATERIALS

Aluminium frames

Cheap (thick-walled) aluminium frames. These frames are very strong, they could have the fittings required on a touring bike and they should last a lifetime but they are heavy, very uncomfortable and they have a “dead” feel. Have you ever heard of an Aluminium spring?

Expensive (thin walled) aluminium frames. These frames are less uncomfortable and they are quite light but they can’t have the fittings required for touring and they break! Dealing with a broken lightweight aluminium frame is easy – recycle it into bottle tops!

Carbon frames

Carbon makes a perfect spring; Carbon fibre frames can be very lightweight and very durable – as long as you don’t scratch them – a gouge in a carbon frame is a catastrophic failure waiting to happen. I’d have no hesitation using one for racing – if I raced – and of course, if somebody else was paying for it! Try Googling “cracked carbon” and see what pictures you get! It’s difficult to manufacture a carbon frame with luggage carrier bosses – I don’t know whether to laugh or cry, when I see a “cool” carbon road racing frame being used for lightweight touring – I see rattling mudguards, held on with cable ties, which have been known to suddenly jam in the wheel, precipitating an instant cart wheel, followed by a face plant. I see mega heavy alloy seat post-fitting (seat post breaking?) carriers with loads being carried, which are too high and too far back for stability. Alternatively, I see no provision for luggage at all; as the day warms up, the rider end up looking like a cricket umpire, with clothing tied around their waist – how cool is that – in both senses of the word? With most of these adapted road racing frames, I frequently see the dangers and difficulties associated with toe overlap.

Titanium frames

I hear it said that Titanium frames ride like steel frames. That’s true – in my opinion, a top quality Ti frame is almost as nice to ride as a top quality steel frame! It can be argued that Titanium can be used to make springs but until Samurai swords or GLOBAL kitchen knives are made from titanium, I will continue to believe that steel is a superior material for many applications. Titanium is two-thirds of the weight of steel – but even the top quality, cycle-specific tubes are much less stiff. To make a frame which is as stiff as a good, high quality steel frame, requires a larger volume of material, which erodes most of the weight saving! The majority of customers however want and expect, a weight saving with a Ti frame, therefore they end up with a frame which isn’t stiff enough – this not only wastes energy – it can sometimes give a scary ride down steep hills – particularly if it’s a short wheelbase frame with road racing geometry!

II. Does weight matter?

In the real world, what is the cost, in terms of energy expenditure, of riding a slightly heavier bike? If you disregard rolling resistance and aerodynamics (which I discuss elsewhere) the equation used for calculating energy is:

Kinetic Energy (KE) = 1⁄2MV2

Thus, a 75Kg cyclist, with 5Kg of luggage on an 11Kg bike, would use on average 202W of power to accelerate from 0 to 24Kph (15mph) in 10 seconds – if the same cyclist, wearing the same clothes and riding in an identical position, had a 6.5Kg bike and carried no luggage, they could reach 24Kph in 9 seconds, from a standing start, for the energy expenditure of 204W.

If you used all the bits from a 6.5Kg Tour de France bike on one of our medium sized Audax frames, you’d swap a 1kg frame for a 2.1Kg frame – you could use the same carbon fork. This would mean that our Audax bike would weigh 7.6Kg. The fact that the components would be unsuitable for use as reliable transport, is irrelevant to this comparison.

Let’s see the difference in energy expenditure between a 75Kg rider, with no luggage, riding from 0 to 24Kph in ten seconds on each of the above bikes. I will disregard rolling and air resistances, because they will be virtually identical in both cases.

A 75Kg rider, on a 6.5 kg bike, would use 181.1W.

A 75Kg rider, on a 7.5 kg bike, would use 183.5W.

That’s less than a 1.31% difference. Once up to speed, given identical riding positions and identical tyres, there’s virtually no difference whatsoever in the amount of energy required to maintain this speed – on a flat road – apart from the aerodynamics of the frame itself. A nice, slim steel frame is almost certainly more aerodynamic than a mid range, fat carbon frame – now there’s a thought!