Mavic continues to make a Road racing crank set, and wisely uses the 130mm bolt center diameter chainring pattern. The arms are like the 637 set forged of 2014 aluminum alloy with Numeric Controlled milling machine work to make the arms perfect in shape. They are also straight so sighting down the end will reveal any bends. The arms are 33.75mm wide at the pedal spindle, and narrows to 25.08mm slightly above the pedal. The left arm widens to 33mm just below the B/B spindle and is 41.22mm at the center of the B/B spindle. The right arm has an expansive manta ray shaped spider made then machined with the right. The spider has a thickness of 5mm over most of its area, but becomes thicker at the spider arm ends. The 631 cranks don't use a conventional outer fixing bolt set, instead it uses 4mm long aluminum spacer between the inner and outer chainrings. A Black steel fixing bolt passes through the inner chainring, then spacer, then outer chainring and anchors into the back of the spider arm.
The outer chainring has an anti-jam pin. 631 cranks come with machined from aluminum rod crank arm caps, left in an un-anodized Silver. These cranks will work with any 2 degree, tapered spindle, bottom bracket, (Mavic prefers theirs). The cranks are made in 165mm, 170mm, 172.5mm, 175mm, 177.5mm, or 180mm lengths with 39-53 tooth chainrings. We found the Mavic 631 crankset has a Bike-Pro Q measurement of 134mm. Mavic 631 cranks come as right arm, with spider, two chainrings, the required fixing bolts, left arm and a set of machined aluminum crank arm caps. The 172.5mm crankset, with all included parts, weighs 722.5 grams, the 175mm set weighs 727 grams.
Length-65-70-72-75-77-80 $ Price in Catalog