According to Shimano's website, you can get the Ultegra double crankset in 180 mm length. I can't find this crankset anywhere (from the bike shop or the internet), only found in Dura-Ace. Does it even exist? If so, where can I get one?

Thanks.

Why do you want a 180mm crank? There is no reliable formula for predicting crank length. There ARE lots of formulas out there, but they are just figments of the imagination of their purveyors. No one has ever done a study that shows how crank length should relate to anything. Probably the best work done on this VERY difficult to research topic was by Lennard Zinn. He unintentionally showed how our adaptability was more important than our size or riding style. He's sure that the results of his study are wrong, but he just can't seem to find any data to support his pre-conceptions.

You will find no high quality data to support any particular crank length as being better than any other. This is true whether or not you correct for leg length, femur length, etc. On the other hand, you will find lots of anecdotal or low quality data to support all kinds of conclusions, and more theories than you can shake a stick at. A rider's response to changes in crank length is 1) highly individual, 2) dependent on riding style and the event (TT, climbing, crits, track racing, etc.), and 3) most important, highly adaptive. This is why it is so hard to study the effect of crank length.

It is generally the case that longer cranks make it harder to spin, and high cadence is the best way to minimize knee problems. That said, an extra 5 mm in crank length may only take away 3-5 rpm of spin, so it is not a large effect. Spinning is more physiologically efficient, all else equal.

I've never seen it. Don't think that it exists.

I guess the reason why I thought I might like 180mm cranks is because I'm 6'6" rider, and I currenly have an Ultegra 175mm triple. I want to transition to a double crank, because I never use the little sprocket, and I like the feel of the more narrow crankset. So I thought maybe I would give the 180mm a shot. But if the payoff is minimal, it's probably not worth the trouble of finding one.

Thanks for the feedback!

I had a 6'7" customer who wanted 180mm cranks on a new Santana tandem. Santana is a direct importer of Ultegra tandem cranksets, but even they were unable to obtain 180mm cranks for the captain position. The solution was a drilled out Dura Ace crankset with inserts for threading the pedals on the opposite sides.

I could see using 180's if I was 6' 5"