Carbon/aluminium or aluminium handlebar stem?

Work proceeds slowly on the RCUK test Enigma Ethos all-rounder.  As ever with my new builds, the first task… er, the first task is to get it home, followed usually by fitting the headset and fork and then a pair of wheels. At this point I can determine the stem length and, before cutting down the steerer tube, decide on the handlebar height required to get my favoured riding position.

The latter can be got to within whatever thickness of stacking spacers are available, so 5mm easily and 1mm with some difficulty if it is that important. Handlebar horizontal placement depends largely on stem length increments, which in practice, since they come in 10mm increments, means it can be got to within 5mm of the position required. I doubt many cyclists can feel a difference of 5mm in the position of the bars and saddle relative to the bottom bracket, all other dimensions being the same.

On measurement, it turned out a 130mm stem was 8mm too far forward. Going to a 120mm stem would make this 2mm too far back, which I can live with. I ordered a PRO PLT 120mm stem from Madison and received instead a 120mm PLT CC model. This baby is made by wrapping carbon twill around an aluminium forging and bonding the two materials together.

The carbon twill finish is all very well and indeed very nice if it is what you want. However, it isn’t quite what I had in mind for the Ethos, which boasts polished lugwork and a steel fork. So I requested a sample of the original request. When it turned up, it proved to be the same weight at 125g. The plain PLT is forged from 2014 aluminium alloy, while the non-carbon part of the CC version is forged in 7050 alloy. Both alloys are high-strength; it is not obvious why both stems should not be forged in the same alloy unless the 2014 is stronger while the 7050 is better suited somehow to bonding.

In any case, their weighing the same means there must be more metal in the PLT. The addition of a carbon wrap of the same weight as the missing metal might be expected to add stiffness, since carbon is a lot stiffer than aluminium. However, the bonding agent between the two, which must transmit loads between them,  is a not-very-stiff epoxy resin. It is likely to stretch or compress rather than transfer said loads directly, surely negating any stiffness benefit the carbon wrap might have conferred.

Given that they weigh and most likely perform the same, the £50 price premium for the CC seems a lot to pay for the carbon finish. While fine if a carbon look is wanted, it isn’t here. Back has gone the CC, while the PLT will kick the Ethos build forward a step.

PRO PLT stem £39.99

PRO PLT CC stem £89.99

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