All About Extensions

All About Extensions

One of the biggest sources of confusion among triathletes is which extension shape is the best. You hear things all the time regarding different shapes, and why they are better or worse than others. "Ski bends are more ergonomic" -- "Ski bends are less ergonomic" -- "Straight extensions are only for Tour de France prologue specialists" -- "S-bends will kill your wrists" -- "The new Ultra-Lazy Super W-bends are the only extension anyone should ever need" -- do any of these sound familiar? Are you confused yet? Fear not - we're going to take some time to discuss different extension shapes, and why, in fact, they ALL have their place. Yes, every extension is usable, even for iron-distance triathletes.

It's important to start with a basic premise: we want the shifters to be close to the same plane as the top of the arm pads. Meaning, if you have the bike level to the ground, the arm pads and the shifters will be at close to the same height above the ground. (If you are one of the few who needs your extensions tilted to the sky, then we're actually talking about the plane that's parallel to the two axes of your extensions. The rest of you can ignore that last bit.) Some will prefer a shifter that's slightly above the pads, and others slightly below. But probably not by more than +30mm/-20mm.

Extensions vs Stack

Straight extensions work fine, if your pad stack is low enough.

Where the confusion sets in is that every aerobar has a different relationship between arm cups and extension clamps. On a Zipp Vuka, for example, the arm cups sit several cm above the top of the extensions. On a 3T Brezza, the pads are basically at the same level as the top of the extensions. On some bars, the extensions and the pads rise together (like on the Trek Speed Concept 9-series). On some, only the pads can rise (like the aforementioned Zipp Vuka). Some rare bars have the ability to adjust both pad stack AND extension stack, like the Pro Missile Evo, or the SC9 bar with our custom hardware on it. Matching the right extension to YOUR BAR is a matter of knowing that stack difference, and finding the extension with an appropriate amount of rise. For example, a straight extension can work well on a bar where the arm pads are right on top of the extensions. Chris McCormack rode straight extensions to great effect at the 2010 Ironman Hawaii, because his Shiv's arm cups sit right in line with the extensions. Those extensions would be a BAD choice on a bar with a big extension-pad stack difference like the Zipp Vuka.

You may have already heard some advice about extension height vs pad height. Some editors write about extension height, and leave it at that. But that isn't the end-all about extensions. Far from it. There are two other very important aspects about what extensions will be appropriate for a given rider.

Hand Width

Many riders benefit from rolling extensions inwards, but keep in mind, that alters the stack equation.


One metric often ignored is hand width. For the most part, bikes are pictured and sold with extensions running with their shape completely perpendicular to the ground - that is, with no roll. However, a LOT of riders find it more comfortable to roll the extensions inwards, bringing their hands closer to touching. It's easy to see why. Stand up and hunch over, put your arms in the aero position as if you were riding. Now, bring your elbows very close together, and then try to separate your hands as much possible. Very quickly, you'll start to notice a lot of strain in your deltoids. Bring your hands together, and the strain goes away. Voila. However, rolling the extensions in will reduce their effective height above the pads, (unless you're running straight extensions). So you have to factor that in to your extension choice. I'm currently riding a set of Zipp Chicane (S-Bend) extensions, which rise 40mm (kudos to Zipp for supplying this info right on their site), but I roll them in until my thumbs touch, and they only rise about 30mm now. With the top of my pads just 10mm above the extensions, the shifters are about 20mm above that plane. Perfect.

So, with these two bits out of the way, let's talk about the meat of the problem - the shape itself, and how it responds to rider movement. Click below to get to page 2 of this feature.