Sims Cranks

SIMS TITANIUM LITE-NING MOUNTAIN CRANK ARM SET

Sims uses nearly the same numerics in controlling their lathe to have the CNC station turn out Titanium 6Al-4V versions of their aluminum arms. But first, a reality check! If you read our metals section you know that the 7075-T6 aluminum alloy most of the numeric controlled arms are made of, is as strong as about anyone needs. Also in the Metals section you are told that Titanium is 60% heavier by volume than aluminum. Titanium's real virtue for crank purposes is enhanced stiffness, not weight reduction as a substitute for the already lighter aluminum. Now, that being said, we know that are people who want expensive and exotic, and very stiff un-yielding crank arms, these cranks are for them. The left arm is made with the same style as the aluminum version. The width at the pedal spindle end isn't quite as wide, just 21.81mm and gradually widens to 36.7mm at the B/B spindle. The Ti arm is only 24.67mm thick at the B/B spindle. The right arm uses two piece construction, with the spider made as a separate piece from aluminum.

To machine the arm and spider from a single piece of Titanium would have wasted a great deal of expensive metal because the piece it would be cut from would have to be at least 125mm wide and 25mm thick and 250mm long. By making the arm and spider separately, the arm can be cut from a piece that is 40mm x 25mm x 210mm less than a quarter by volume of the single piece size. The spider is made of 7075-T6 aluminum alloy, made exactly like as the one on the aluminum arm. Added weight reduction on each of the spider arms is achieved from 9.5mm holes drilled through each near the arm.

The spider has a 22.62mm hole which fits over a fitted square protrusion on the back of the arm. The spider is pressed into place and further held by three small steel bolts. This spider uses the same 110mm and 74mm Bolt pattern of the aluminum model. Crank arm dust caps are also provided with the Ti cranks. The caps are again made of aluminum but have a 5mm hex fitting to tighten them in place instead of the single straight slot of the aluminum arms. The Ti arms are polished after being machined, and are discernible by the hex fitting on the cap, the two piece right arm construction, and the Silver aluminum spider is slightly brighter than the polished Ti arm, giving the right arm a two tone appearance. They are made only in a 175mm length. The Lite-Ning Ti Mountain cranks come as right arm, with spider, left arm and a set crank arm dust caps. Chainrings, the double chainring fixing bolt set, and the inner fixing bolt set, will be needed separately. We found the 175mm arm set weighs 476 grams, the caps add another 3.5 grams. Made in Santa Ana, California.

	Mountain arm set $ Price in Catalog 



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