Campy Record cranks are forged from aluminum alloy, with the pedal spindle holes drilled and tapped with 9/16" by 20 TPI threads. The crank arm dust cap holes are bored and tapped with 22mm by 1mm threads. The square tapered hole for the B/B spindle is bored then broached. Each of the arms is hand polished then Silver (clear) anodized. Which aluminum alloy is used, Campy doesn't state in their statistic starved brochure. The arm is 34mm wide at the Pedal spindle, narrows to 28.5mm and on the left arm becomes 37.5mm wide at the B/B spindle. The right arm has an edge milled around the integrated spider.
The Record crankset uses a principle that Campagnolo innovated which has come to be known as the "hidden fifth arm." All present common chainrings have a bolt pattern that uses five fixing bolts, this generally leads crank maker to have a spider that has five arms. Campagonolo Record and Record OR cranks have the fifth spider arm hidden below the crank arm itself, this saves a slight amount of weight and makes it nearly impossible for that spider arm to bend. The outer chainring has a steel nutsert pressed into it for a fixing bolt to anchor into. The fixing bolt for the "hidden fifth" passes from the inner side of the inner chainring, through a forged extension on the arm for the chainrings to rest against, and through the outer chainring. The outer chainring is die-cut from 4mm thick aluminum plate, then turned on a lathe to taper the teeth and thin the chainring to make shifting easier.
Steel rivets, just below the teeth, are positioned to assist the chain onto the chainring. The outer chainring also has an anti-jam pin. The inner chainring is die-cut from 3.5mm thick aluminum plate, then turned by lathe to reduce the thickness of the teeth to 1.86mm. The chainrings use a 135mm bolt center diameter. Campagnolo is the only crank maker to use pattern. There is one mechanical for them to continue using this pattern and that is "the distance from the bolt center to the chainring outer edge is a shorter distance, therefore the aluminum is less likely to bend." In practice a one tooth difference, using a 53 tooth 135mm chainring has the same 43mm span as a 52 tooth 130mm chainring, so this isn't a real advantage, and the outer is made from 4mm thick plate that is sturdier than many 130mm pattern makers use.
Many people in the bike industry agree that the real motivation is to obligate the owner of a Campy crank to buy only expensive Campagnolo replacement chainrings, since no one else makes a 135mm pattern Road ring. Each of the Record arms uses the Campy "built-in extractor." Many avid riders will remember when Shimano around 1981 introduced their "one key release," the differences between the Campy and the Shimano are hard to tell. A Chrome plated steel bolt threads into the crank arm, having a 6mm hex fitting on the outer end. A steel crank arm cap threads into the arm with a 15mm hole through it. The cap when tightened into the arm exposes the bolt head. Turning the 6mm counter-clockwise pushes the bolt against the steel cap. Further turning of the bolt pushes the arm off the B/B spindle. Turning the bolt clockwise pulls the arm onto B/B spindle for installation.
Record cranks come with chrome plated steel outer fixing bolts. We found Record cranks to have a Bike-Pro Q measurement of 150mm. The Record crankset is compatible with any two degree tapered spindle B/B. Record cranks are available in 170mm, 172.5mm, 175mm or 180mm. They come with the 42-52 or 39-53 tooth chainrings. The Record cranks come as right arm, left arm, two chainrings, the required fixing bolts, and the arm pulling crank bolts. The 172.5mm 42-52t crankset, with all included parts, weighs 720.5 grams. Specify length and chainring sizes. $ Price in Catalog
Campagnolo Chorus Crankset