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Nov

2

2012

Building a Cyclocross Bike

specialized-crux-cyclocrossSydney Fox (right) on course at CrossVegas with the Specialized CruX. Photo by Daniel DunnOn the cyclocross course, I’m prone to crashing and taking corners painfully slow. Neither habit boosts me to the front of the pack. But at CrossVegas in mid-September, I demoed a Specialized CruX carbon that helped my performance and made me believe in an elusive cross victory. It was stable, smooth, and cornered precisely. I sat down with Andrew Frasca, the lead bike engineer, and Ned Overend, a Mountain Bike Hall of Famer and a podium finisher at the 1985 cross national champs, to find out what separates the CruX from the cross field.

 

Ned, you’re a legendary endurance athlete. How important is the bike?

In any discipline, the engine is key, but having confidence in your equipment is important whether you’re a beginner or a pro. There is more crashing in cross than road or mountain bike racing. It’s just the nature of the slippery conditions, the skinny tires, and the short races, which make the pace frenetic. Having confidence in your bike will let you put more focus into going fast.

 

Ned, why did you want to be involved in designing and producing the bike?

It started with the Tricross model—our re-introduction to cross, which was a bit of a compromise between a touring bike and a cyclocross bike. After a couple years racing the Tricross, it was obvious we needed a cyclocross-focused model. Using our own experience and the feedback from the Cal Giant Strawberry team, our regional CX teams, and Todd Wells, we looked at what we liked about the Tricross and what we needed to improve on. I’ve always been passionate about cross and I’ve been a longtime advocate at Specialized for developing a great line of cross bikes.

 

What’s the advantage of a bike with cross-specific geometry rather than a road bike with knobby tires?

Andrew: Cross bikes began as road-oriented bikes, but there are many details that differ. For one, cross is primarily a fall/winter sport. For many parts of the world that means snow, rain, and mud. Tire size and clearance is key. Mud builds up in areas where the tire passes closely to the frame—specifically the chainstays, seatstays, and brake areas. Road bikes don’t offer enough clearance. And road bikes use caliper brakes, which don’t offer enough tire or mud clearance to be a solution. Cross bikes are designed for either cantilever or disc brakes. You want a stable but fast-handling bike for most cross courses, where tight cornering and quick acceleration bursts require a predictable bike. This means you play with headtube angles, fork offsets, and bottom bracket heights.

 

What separates the CruX from other cross bikes on the market?

Ned: First, a relatively low bottom bracket height. I can feel the lower center of gravity in many cornering situations, but especially when there is a series of “S” turns that require throwing the bike back and forth. A lower bottom bracket also requires a little less energy to hop back on, which becomes more obvious the more tired you become.

 

Second, the stiffness of the head tube/fork area gives me confidence in the corners. If the front end flexes during a rough, high-speed, off-camber corner, the bike will tend to drift to the outside. If the front end is stiff, the bike will hold a more precise line and the steering will be predictable when you need it most. The stiffness in the bottom bracket area makes the CruX really efficient when you stand up and sprint out of a turn, which is one of the definitions of cross racing. You want to get back up to speed as fast as possible coming out of a turn. Also, the bike is light, which is especially helpful when lifting it over barriers or running up a long flight of steps. 

 

Andrew: The tapered head tube really ties into the size of the joint where the down tube meets the head tube. With tapered head tubes, you have more material at the head tube/down tube joint and that greatly improves front-end stiffness. On carbon bikes you can get improved fiber alignment and take more advantage of larger surface areas. Head angle, fork offset, and the resulting trail—the horizontal distance measured at the ground between the head angle centerline and a vertical line dropped from the front axle—all work together to impact handling. There are other aspects of frame geometry that factor in, but in general, if you have a short trail, you will have pretty quick handling, whereas a longer trail equals more stability.

 

You have to find that magic balance between twitchy handling and stability that is appropriate for cross bikes. We put a lot of time and energy into determining the rider’s needs. It’s not fluff. One of the first questions asked in many of our project planning meetings and all the way through the design review process is, “How will the rider benefit?” We have a pretty established focus here at Specialized. If it’s not an improvement that benefits the rider, why bother? During the development process we test a number of iterations, we try new ideas, we ask questions and listen to the answers. We focus on ride quality and performance. The feedback we’ve been getting on the CruX indicates our efforts have paid off. 

 

What is your take on disc brakes for cross?

Andrew: I am all for disc brakes. Of course, the industry is in transition and when the cross/road-specific disc brake technology advances to the point that they are as good as mountain bike brakes, there will be no turning back. I can certainly appreciate the perspective of the purists, and I think the cantilever option will be around for a long time to come. With that said, the performance benefit of disc brakes on the horizon cannot be ignored. It’s a little short sighted to discount disc brakes based on the brake tech available today in cross. It is going to improve by huge amounts. —Syndey Fox

 

Learn more at specialized.com.

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