Precision Tooling is a family owned machine business that has machined parts from metal for different companies over time. For a period they were the sub-contracting firm making CQP cranks. The relationship with CQP faded and John Trenerry and his father Phil worked out an exciting and stylish design for a crank arm set. Phil's knowledge of metals helped make the arms strong though they appeared delicate. There was initial un-certainty about whether the family should be bold enough to enter the bicycle parts market on their own, under their own name. As it turns out Phil Trenerry had known John Grafton for many years and Grafton's first cantilever brake had been successful. Grafton had been prevailed by others make an entrance in the crank market and the Trenerry's crank held promise though they again were reluctant. The Trenerrys agreed to make the crank they had designed and let Grafton market them. The crankset's popularity and the Grafton name identification lead to immediate market interest. After about a years time we started to be sold the cranks directly from Topline, (which is also known as Precision Tooling), because their verbal contract with Grafton had crumbled. The design remained rightly in the Trenerry hands and they have become very successful using their own name in marketing their own cranks. We've found that generally when splits like this occur, there is usually a problem related to sub- contractors being paid for their work. Have you noticed how similar the Sims cranks are to the last version of Grafton cranks? It's not a well kept secret that Sims was the sub-contractor used to make Grafton cranks after Precision Tooling (Topline)/Grafton relationship ended.
Precision Tooling first crank under the Topline name was this Mountain crankset. The arm set is made of strong, lightweight 7075-T6 aluminum, elegantly machined in simple shapes with fine finish work. The arms are turned on a lathe from aluminum billet to create the shape of a ball at each end, joined by the slender, tapered arm. The back of the large, 35.5mm diameter ball of each arm is milled to make the arm offset, as is the pedal boss face and the crank arm bolt area. One of the differences in these arms over other American makers is that the back of the pedal boss isn't milled away. Top Line retains the 24mm diameter ball shape at the pedal, drills and taps the pedal threads, leaving the back of the pedal spindle enclosed in the arm. There is a certain elegance to it. The bottom bracket spindle hole is drilled, then the sides are tapered by fine numeric milling. The crank arm bolt recess is drilled and cleanly tapped with 22mm by 1mm threads for the arm dust cap. The top and bottom of each arm have an expanding groove milled into them. This reduces weight without compromising the integrity of the arm. To accommodate wider cage front derailleurs, and reduce weight, the back of each arm is milled in a flat, smoothly curved radius. Each of the arms is given a high polish and then anodized. The spider is made of machined 1/4" (.250") aluminum plate. It is cut to shape, milled on the top and bottom of the arms for the chainrings, drilled and tapped for the fixing bolts. Then it is high polished and anodized in a color to match the crank arms. The spider threads onto the back of the large ball and a stainless steel pin is driven into it from the rear to secure it rigidly and permanently in proper place. This crankset is compatible with all 2 degree tapered bottom brackets, and uses the standard 74mm and 110mm bolt pattern. The cranks come anodized in Black, Blue, Pewter Grey, Lavender, Silver, or High Polished un-anodized silver. We stock them in 170mm, 172.5mm, 175mm, 177.5mm, or 180mm lengths. On a special order basis we can order the cranks anodized in Gold, Green or Red, and we can also special order any of the colors mentioned in a 165mm or 167.5mm length if needed. The Topline Mountain cranks had a Bike-Pro Q measurement of 156mm. Top Line Mountain 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 and crank arm dust caps will be needed separately. We found the 172.5mm arm set, with spider, bolts and spacers, in Black weighs 445 grams. The 180mm length in Lavender, with spacers and bolts weighs 473.5 grams. The inner bolt and spacer set provided weighs 33.5 grams. Be sure to specify length.
Size-165-167-170-172-175-177-180 Color-B-BK-G-GN-GY-HP-L-R-S $ Price in Catalog
Topline SLS Mountain Crank Arm Set
