THM Clavicula SE crankset
According to its creator, the Clavicula SE is the oldest carbon crank design in the world… and still the best
Iproduced the first Clavicula crankset way back in 1993 for the bike brand Storck, when I was pretty much a one-man band,’ says Thomas Mertin, co-founder of the German carbon fibre brand THM. ‘At that time there were no other carbon crank designs so we had nothing for reference. Needless to say, the design has been refined somewhat over the years. For example, initially we designed the cranksets to suit a squaretaper axle, but quickly found out that didn’t work so well in carbon.’
The Clavicula’s current form is the result of nearly 25 years of research and development. It now features a 30mm carbon axle ‘for stiffness and bottom bracket versatility’ and a compact crankset weighs just 293g, which is less than half the weight of Shimano or Campagnolo’s top-end offerings.
‘That said, as much as the design of the crankset has been changed, our ethos has remained the same,’ Mertin says. ‘It has always been to make carbon parts with the absolute best attributes given the capabilities of carbon, regardless of the final cost. We aren’t in the industry to make good products to a price point – we’re here to make the best at whatever cost.’
Mertin and his wife Petra founded the company in 1996 after Mertin was sure he had identified a then-unfilled niche in premium carbon fibre bicycle parts. He left his job as an aerospace engineer but the transition into component production was far from plain sailing.
‘I thought it would be a lot easier,’ he admits. ‘I totally underestimated how difficult it was to design bike parts. The first cranks were such a challenge.’
Yet Mertin credits his naivety as the reason why the Clavicula cranks are what they are now: ‘I started from a blank slate, from the ground up. It meant I could analyse the crank design from an engineering perspective with no preconceptions. Every bit of carbon was placed because I determined it structurally needed to be there, not because I thought it should go there.’
Less is more
That attitude helped create a crankset using the absolute minimum amount of material. Mertin explains that there is always a compromise between stiffness and weight, so he aimed to match the stiffness of Shimano’s Dura-ace design, which he considers an industry benchmark, at the lightest weight possible, because he observes that lighter weight improves performance in almost all cases.
‘That is particularly true for rotating parts,’ he says. ‘Overcoming more inertia costs more energy, which people know is true for wheels but don’t really consider for cranksets. They rotate too, so it isn’t really any different.’
Yet Sram has a carbon crank design, as does Campagnolo, so how can the Clavicula come in at half the weight? Surely there are some secret materials at work here?
‘No, we aren’t illusionists, just engineers who know their stuff,’ says Mertin. ‘We use what’s available to everyone else – high-modulus and high-strength fibres from Toray or Tmax or whoever can offer the best deal at the time. We just know better than anyone where to put the material and where not to.’