Tom Ritchey has reworked the mountain crankset to reduce weight and increase strength in needed areas. The Logic crankset is made in Japan by Sugino (who also makes the cranks sold under the Specialized name), following Ritchey's specifications. The crank arms are among the first of Sugino's new cold forged products. Cold forging again is the process of squeezing within a die form aluminum into a shape, then annealing (cooling it), then squeezing it again and annealing it until after the use of several dies it assumes the desired shape. After the arms are cold forged out of aluminum alloy, they are drilled for crank dust caps, fixing bolts, pedal and B/B spindle. The B/B spindle hole is broached to give the needed square sided, 2 degree taper. The dust cap hole is tapped with 22mm x 1mm threads, the pedal spindle holes are tapped with 9/16" by 20 TPI threads. Each of the arms is high polished by hand on the outer face, top and bottom sides, (the rear of the arm is lightly polished, the rear of the spider isn't at all) then clear (Silver) anodized. The arms have a flat surface for the face, top and bottom, making stress fractures easy to spot.
To reduce weight, one of the five arms on the spider section of the right crank arm, has been eliminated. Notice how most other cranksets have five? The fifth arm on the Ritchey crank, actually exists on the back side of the crank arm itself, where the spider, and the arm meet, (this is a style borrowed from the Campagnolo C-Record crankset, now used on the Campy Record and Record OR). This eliminates a slight amount of aluminum weight though the steel bolt and nut (fixing bolt) to hold in place are still needed and used. The crankset was designed with a low Q-factor as an objective. These Mountain cranks are said to have a 151mm Q factor, which is the distance from outer crank facing to outer crank facing with the two arms properly and securely fastened to a B/B spindle. (How well seated and tightened the arms are seems to make a serious impact on this measurement) The end of each arm, at the pedal end has the backside rounded slightly, to provide greater chainstay clearance. The left arm is forged with a point, leaving extra mass around the B/B spindle. This extra aluminum helps displace stress on an area historically prone to stress fractures.
Included with the cranks are chrome plated steel crank bolts that have affixed chrome dust caps. These bolts are similar to the "capless" design used by Shimano and have an 8mm hex fitting for removal and installation. A steel washer is included for the cap/bolt to turn against reducing friction. The bolt weighs 16.5 grams, the washer another 2.5 grams. Using a crank arm pulling tool (Park CCP1) will still be necessary to remove the arm without damage. The crankset comes with Silver anodized aluminum chainrings, and all necessary fixing bolts.
The outer chainring is die-cut from 3.66mm thick aluminum plate, then turned on a lathe to taper the teeth, and then the teeth area to 2.06mm thickness. The outer chainring has an anti-jam pin pressed into it at the crank arm, to prevent the chain from bunching up between the arm and rings in an overshift. The middle is die cut from 3.30mm aluminum plate, turned on a lathe to taper the teeth and thickness to 2.03mm. The inner made the same as the middle. The chainrings use the standard 74mm and 110mm fixing bolt pattern. Because the "fifth arm" of the spider is really the crank arm, standard outer chainring replacements with an anti-jam pin won't have the pin usefully line up correctly on the Logic Crank. Replacement with a "Ritchey" or a 110mm BCD outer designed for fifth arm cranks will be necessary to maintain the anti-jam pin functionality. The Logic Mountain cranks come with nickel plated steel middle outer fixing bolts and nuts. The inner set of fixing bolts is also nickel plated steel.
The cranks will work with any 2 degree, tapered spindle, bottom bracket. We found the Logic Mountain cranks had a Bike-Pro Q measurement of 145mm. Ritchey Logic cranks are made in 170mm, 172.5mm, 175mm, 177.5mm, or 180mm lengths with the 24-36-46 tooth chainrings. Logic cranks come as right arm, left arm, three chainrings, all the required fixing bolts, and a set of crank cap/bolts. Logic 175mm cranks with all included parts, weigh 714 grams. The steel crank arm cap set weighs 38.5 grams a pair. When ordering specify length.
Length-70-72-75-77-80 $ Price in Catalog
Ritchey Logic Compact Cranks
