RoadLight

Hi Kontact,

I agree fully, a race vs endurance geometry cannot be defined by the stack height. Wasn't that clear in my previous posts? And this makes the stack-to-reach ratio just as meaningless.

I consider the larger dimensions to be fundamental to describing these kinds of geometry differences. The stack height doesn't provide enough "height" information to reveal the default cyclist body position that the bike targets.

There are two important vertical dimensions. They are the handlebar height above the front wheel axle and the bottom bracket depth below the wheel axles. If you want a single height dimension that encapsulates it all, it would be the height of the center of the handlebar above the center of the bottom bracket.

I haven't commented on the horizontal dimension before now. Unfortunately, it's the most complicated because the frame's seat tube angle causes it to change with the seat post height. As soon as you change the seat post height, the horizontal dimension changes. The horizontal dimension is the distance from the center of the saddle clamp at the top of the seat post to the center of the handlebars. I suppose that manufacturers need to provide two values, one with the seat post at its lowest position and one at its highest position.

Those are the major dimensions that will reveal what kind of cyclist posture a frame and fork are designed for. It's the target cyclist posture that plays the biggest part in determining the type of "geometry" a bike is designed for. But it's not the only thing. There are many other aspects to bike fit and the quality of the ride that distinguishes one classification from another. But they are lesser aspects compared to the cyclist posture on the bike.

As for the Specialized Roubaix, you need to read the frame description farther down its product page on the Specialized website. It states that the Roubaix has what Specialized believes to be an "endurance geometry". Which makes perfect sense considering the kind of routes that it was designed for. Specialized's use of the phrase "performance road bike" is general in scope. If you look at the models they list under that heading, you'll see the Venge, Tarmac and Roubaix among others. As far as I'm aware, the only model in that group that Specialized says has an "endurance geometry" is the Roubaix.

We need to be careful that we don't jump to the wrong conclusion based on observed use. As you've rightly pointed out, a mechanic can configure a road racing bike for an endurance posture and visa versa with their choice of stem, handlebar, steering tube height, seat post height and saddle choice. I've seen pros use an aero road bike for climbing. That doesn't make the aero bike a climbing bike. All it means is that the cyclist prefers to use an aero bike even when climbing. The same is true for an endurance bike. You might see a pro cyclist using an endurance bike like a Roubaix for routes that have no cobbles. The cyclist may prefer the extra shock absorption provided by a bike, like the Roubaix, that's been designed for cobbles. These kinds of crossovers of bike application are not uncommon.

Finally, please remember that each manufacturer has their own opinion of what constitutes one class of bike vs another. Cervélo's idea of an endurance geometry is undoubtedly a little different than Specialized idea of an endurance geometry, and so forth. These classifications are a little loose at the edges. For some manufacturers, the only difference between a race geometry and an endurance geometry is the size tires the frame and fork can accommodate. Personally, I think that's way too narrow of a view but it appears to be a view that some manufacturers have.

Kind regards, RoadLight