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From the pages of Velo: Stiff & Stones

Where The Rubber Meets The Road

If there is one thing we have learned from our endurance bike testing and our years of talking to pros and mechanics at the cobbled classics, it’s that tires are supremely important to comfort over rough roads.

After lab testing each bike with its stock tires, we then did vibration testing on each using the set of Fulcrum Racing 4 wheels that came on the Specialized Roubaix, including the Specialized Roubaix Pro II 25mm tires. The supple 120tpi tires with the larger diameter (most of the bikes came with 23mm tires) changed the results on the large-bump roller test significantly. The Lapierre went from 3.03G down to 2.68g and the Cannondale dropped from 2.76G to 2.38G.

We settled on testing each bike at 90psi in the stock and normalized tests after riding the bikes at 100psi produced peaks that maxed out our accelerometers.

After extensive ride testing in Colorado using the stock tires, we shipped the four test bikes to Belgium with 25mm Michelin Pro Optimums installed. Between the four test riders, we didn’t experience a single flat during the cyclosportifs of the Tour of Flanders and Paris-Roubaix, using pressures of 70-90psi. (Nick did flat once bombing back down the Oude Kwaremont on our photoshoot day when he hit a particularly gnarly patch of partially upturned cobbles.)

This year at the real Tour of Flanders and Paris-Roubaix, we took a close look at what the pros chose to ride over the cobbles. Most ran tires at least 25mm wide, with many selecting 27mm options for Roubaix. Leopard-Trek rode 27mm FMB handmade tubulars and Saxo Bank chose Specialized-branded Dugast tires that were stamped 27mm but looked even wider when inflated. Tire pressures varied by rider, of course, but most selected something under 80psi. Race winner Johan Van Summeren, for example, ran 65 and 73psi, front and rear — and he weighs 170 pounds.

If a new bike is not in the cards for you this year, the takeaway from all this is simple: When you want a more comfortable ride, put on bigger tires and go easy on the floor pump. —BEN DELANEY

Torsional Stiffness

The torsional stiffness test we co-developed with Microbac Laboratories, Inc. measures how a bike moves at three different points while subjected to a simulated pedaling force. Here’s how it works.

The front fork is fixed. The rear dropouts are mounted to a dummy axle that pivots on a eyebolt, allowing the rear of the bicycle to twist and move laterally. A chain is connected from the large chainring to the dummy rear axle to transfer the pedaling force through the rear triangle.

Dial indicators contacted the bike at the center of the drive crankarm’s face, at the top of the head tube and at the top of the seat tube. Two 50-pound dumbbell weights were hung on a spindle screwed into the left crank positioned horizontally forward and the values were recored on the three dial indicators. —LENNARD ZINN

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