These cranks are machined from solid pieces of 7075 T6 aluminum stock. Each of the arms is turned on a lathe to produce the tapered shape, with a 37.72mm diameter ball at the B/B and a 29.14mm diameter ball at the pedal end. The ball shapes are then milled flat with the specific angles required for the spider and pedal and B/B spindle installation. The pedal end ball is drilled through and tapped with 9/16" by 20 threads per inch threads for the pedal spindle. The crank arm dust cap hole is bored and tapped with 22mm by 1mm threads, (no caps are provided with this crank arm set). The square B/B spindle hole is milled with 2 degree tapered sides when the rear of the arm is machined. The back side of the arm is drilled and tapped for a Torx bolt that holds the spider to the rear of the arm. The rear of the large ball has three steel pins driven into it. These pins are used to fix the precise position of the spider on the arm before the Torx bolt holds them together. The crank arms are high polished, and then anodized. After anodizing, the Cook Bros. logo is finely engraved on the face of each arm. The spider is machined from a single piece of 6.63mm thick aluminum plate stock. It is cut to shape, then drilled and tapped for the chainring bolts where needed. The arms have a 6 degree offset for chainstay and ankle clearance, and come with a triple chainring spider (adapter) with threaded inner ring bolt holes. The chainring bolt pattern is the standard 110mm outer, 74mm inner. The crank arm set will work with any standard 2 degree tapered bottom bracket, and naturally Cooks recommends their own sealed bearing bottom bracket. The crank arms come anodized in Black, Purple, or Silver with the spider anodized in Black. We stock them in 171mm, 176mm, or 181mm lengths. We found the CBR Mountain cranks to have a Bike-Pro Q measurement of 168mm. Cooks CBR cranks come as right arm with spider, left arm, and a set of five steel inner chainring bolts with aluminum spacers. Chainrings, the double chainring bolt set, crank bolts, and crank arm caps will be needed separately. The 176mm arm set with spider in Black weighs 507.5 grams. The inner bolt set provided weighs an additional 35 grams. Be sure to specify color and length.
Size-71-76-81 / Color-BK-L-S $ Price in Catalog
The Cook Bros. Racing RSR cranks are similar in style to the Cooks CBR arms, (the same aluminum stock, 7075-T6) and are made using the same manufacturing techniques, however there are some important design differences. The arm dimension is slightly smaller in diameter, and they have a half-round shaped slot milled down the back of the arms. The milling is to create greater clearance for smaller chainrings, front derailleurs and generally to produce a lighter crank. The left arm of the CBR set, in a 176mm length, weighs 224.5 grams, while the 176mm RSR left arm weighs just 188.5 grams. The 176mm right arm of the CBR set weights 283 grams while the 176mm right arm of the RSR set weighs 248 grams. The spider has been reworked, having all excess aluminum milled away to reduce any extra weight. This crankset is compatible with all 2 degree tapered bottom brackets, and uses the standard 74mm and 110mm bolt pattern. The crank arms are anodized in Blue, Black, Purple or Silver, with the spider anodized in Black, and come in 171mm, 176mm, or 181mm. We found the RSR cranks to have a Bike-Pro Q measurement of 167mm. Cooks RSR cranks come as right arm, with spider, left arm and a set of five steel inner chainring bolts with aluminum spacers. Chainrings, the double chainring bolt set, crank bolts and crank arm dust caps will be needed separately. The 176mm arm set, with spider, in Silver, weighs 436.5 grams. The inner bolt set provided weighs an additional 35 grams. Be sure to specify color and length.
Size-71-76-81 / Color-B-BK-L-S $ Price in Catalog
A compact version of the RSR arms is available, achieved by making the right arm with a spider that has 58mm inner bolt pattern and a 94mm outer chainring bolt pattern. These Hyper Drive-C compatible arms are slightly lighter and compatible with all 2 degree tapered spindle B/B's. They are also made in Black, Lavender, or Silver anodized finishes, with the spider anodized in Black. The Cooks Hyper-C cranks come as right arm, with spider, left arm, and a set of five steel inner chainring bolts with aluminum spacers. Chainrings, the double chainring bolt set, crank bolts and crank arm dust caps will be needed separately. The inner bolt set provided weighs an additional 35 grams. Be sure to specify color and length.
Size-71-76-81 / Color-BK-L-S $ Price in Catalog
Cook Bros. makes a Road model of the RSR cranks using a 130mm bolt center diameter pattern. Machined of 7075-T6 aluminum, the PCH crank arms are made using the same techniques involved the RSR Mountain arms, and have the milled slot on the rear of the arm. The PCH cranks are made anodized in Black, Lavender or Silver with the spider anodized in Black. We found the PCH cranks to have a Bike-Pro Q measurement of 160mm. The PCH cranks come as right arm with spider and left arm. Chainrings, the double fixing bolt set, crank bolts and crank arm dust caps will be needed separately. The 171mm PCH cranks weigh 436.5 grams. Made in USA, specify color and length.
Size-71-76-81 / Color-BK-L-S $ Price in Catalog
The Cook Bros. "E" series cranks are more traditional in their styling. They are machined from 7075-T6 billet aluminum. Unlike the other Cooks arm sets these have a rectangular cross section, not round, and the E cranks use a replaceable, user installed spider. At the pedal spindle, the arm is 27.83mm, it reduces above the pedal to 18.5mm. On the left arm, at the B/B spindle area widens to 37.5mm. The arms are 14.14mm thick at the pedal spindle and thicken to 26.4mm at the B/B spindle. The right arm has five round posts protruding from the back of the arm. These five posts are drilled and tapped for the inner fixing bolts to anchor in. The spider with the outer fixing bolt pattern drilled into it also slides over these five posts. Custom aluminum spacers used with the inner fixing bolts tighten down over the machined plate aluminum spider. The right arm has four stubby extensions that the posts are fastened to. The extensions lie perfectly over the spider. The posts incidentally are positioned so that only a 58mm bolt center diameter can be used for the inner chainring. There are three choices of Bolt center diameter for the spider, either a 94mm BCD or a 110mm BCD or a 130mm BCD. At the moment, the arms are made only in a 175mm length, Cooks believes that they may introduce a 181mm version in 1995. The arms come anodized in Blue, Black, Grey, Lavender or Silver. The standard spider with the 110mm BCD weighs 47 grams, the 94mm spider weighs 34.5 grams. The spiders are available in the same colors. We found the arms weighed 396.5 grams, and had a Bike- Pro Q measurement of 162mm. The inner steel bolts and aluminum spacers weighed 38.5 grams. The E crank set comes as right arm, left arm, spider, five steel inner fixing and the five custom aluminum spacers that hold the inner chainring and spider in place. Chainrings, the outer fixing bolt set, crank bolts, crank arm dust caps and will need to be purchased separately. Specify crank arm color, spider BCD pattern and spider color.
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