THM Clav­ic­ula SE crankset

Ac­cord­ing to its cre­ator, the Clav­ic­ula SE is the old­est car­bon crank de­sign in the world… and still the best

Cyclist - - Ultimate Upgrades - Words SAM CHAL­LIS Pho­tog­ra­phy TA­PES­TRY

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.’

THM Clav­ic­ula SE crankset, £1,099,

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