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Road Gear

Technical FAQ with Lennard Zinn: World’s Freire

Oscar Freire sprinted past Robbie McEwen and Erik Zabel to win stage two aboard the mount that has brought so many victories to Mapei and Rabobank. He was riding a Shimano Dura-Ace equipped Colnago C40, the 2.5-pound frame that won Paris-Roubaix five times between 1995 and 2000. But it is not just another bonded carbon frame, since Colnago’s construction methods C40 are unique and analogous to its method of constructing steel frames. Integral to the C40 are one-piece molded, hand-finished carbon lugs that eliminate the bonding problems and weight of aluminum lugs and are stronger,

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Ready to roll

Ready to roll

Photo:

Oscar Freire sprinted past Robbie McEwen and Erik Zabel to win stage two aboard the mount that has brought so many victories to Mapei and Rabobank. He was riding a Shimano Dura-Ace equipped Colnago C40, the 2.5-pound frame that won Paris-Roubaix five times between 1995 and 2000.

But it is not just another bonded carbon frame, since Colnago’s construction methods C40 are unique and analogous to its method of constructing steel frames.

Mitered tubes ready for the bottom bracket shell

Mitered tubes ready for the bottom bracket shell

Photo:

Integral to the C40 are one-piece molded, hand-finished carbon lugs that eliminate the bonding problems and weight of aluminum lugs and are stronger, stiffer, lighter (and costlier) than carbon lugs made of separate parts glued together. Most lugged carbon builders cut the tubes off straight and stick them into or over the lugs, but then the joint strength is entirely dependent on the lug’s strength. Colnago instead miters each carbon tube precisely, just like the tubes of a welded titanium or aluminum frame (or lugged steel Colnago Master), so each tube fish-mouths around the next tube with complete contact between the tubes. On a welded metal frame, it is obvious that there would be no strength to the joint if the tubes did not have this kind of complete contact to eliminate gaps in the weld, and it also makes a bike difference in a bonded carbon frame. The fully-contacting tubes work together and complement the lug’s strength. In eight years of making C40s, Colnago claims to have never had a single failed glue bond.

Colnago makes C40 lugs in 19 different angles so a wide variety of geometries are possible, and customers can order custom C40s. That’s right – custom carbon frames! And if the airlines damage one of your tubes, Colnago can replace the tube and get your bike back on the road; you need not buy a whole new frame.

The development of the C40 is ongoing. The carbon is now lighter and stiffer, and the stays and bottom bracket have changed since the first of its Paris-Roubaix victories. Early models had aluminum bottom bracket sleeves like most carbon frames. Now, Colnago’s titanium sleeve is knurled on the outside and has four teeth locking into notches in the carbon shell (see photo). It is far more expensive, but it is much better; titanium cannot corrode, and it has stronger threads and bonding.

Another refinement that is not to be confused with similar-looking features on other frames is the “B-Stay” carbon seatstay of the C40. At first glance, the B-Stay may look like the carbon wishbone seatstays currently in vogue on metal and carbon frames. But unlike one-size-fits-all wishbone whose upper end is simply cut off to fit the particular size of frame, the B-Stay is unique to each size and far more rigid.

Each leg of the B-Stay is narrow laterally and deep front-to-back for greater braking stiffness, and the whole structure resembles a tall inverted Y with an cross bridge for the brake, rather than simply mounting the brake at the wishbone crotch as others do.

The bridge creates a reinforcing triangle out of the upper part of the stay, making the system much more rigid than a simple wishbone. Each size frame size has a different B-Stay, with a longer or shorter triangle above the bridge to optimize the stiffness. It would be much cheaper to have one stay and not machine a different B-Stay mold for each size, but it would not be as strong or stiff.

Colnago claims to be the world’s only bicycle manufacturer to qualify for ISO9001, the international standard of quality assurance which was recently renamed Vision 2000 with new rules and certification procedures. By bringing its manufacturing process up to this standard, Colnago can trace each frame back to the smallest detail of material source, lot number, date of manufacture, and people who worked on it. If, for instance, a tubing supplier alerted the company to a defect in a shipment of tubes, Colnago could trace the exact frames the tubes were used on and recall only those specific ones.

“People see a price difference between our bikes and many of the others. But they can’t see the internal details that make our bikes better and worth the price,” comments Alessandro Colnago, Ernesto’s nephew and marketing director. Maybe Oscar Freire can, though.