Tuesday, February 26, 2013

Weighting my Crank

What is the real difference between the 3 generations old Dura-Ace 7800 and  3 generations old Ultegra 6600 crankset? Is Dura- Ace just light weight Ultegra, or what? 
Dura Ace 7800 Crankset
Ultegra 6600 Crankset
As far as weight goes, just 65grams separate the two. 684 grams for Dura-Ace, and 749 grams for the Ultegra. So roughly 2-1/2 ounces. Also the finish on the Dura-Ace is a lot nicer. The Dura-Ace is also shaped a little different. The Dura-Ace is scalloped, where the Ultegra is more like a starfish. While it appears there is extra work involved making the Dura-Ace shape. You have to wonder if it has a measurable difference. Well like I said, the finish and shape is a lot better than the ultegra.
This is something unexpected, the Dura Ace left crankarm is 1 gram heavier. There are shaped a little different, and 1 gram is hardly concern, but like everybody probably expected the Dura Ace to be a little lighter.
The back side of the big chainrings are different. Both Cranksets are 53x39, but if you have engineered the placement for all the ramps and pins to guide the chain through the gear changes, then there would be one optimum geometry. Is one designed to work better than the other? Notice also the shaped of the pins. The Dura Ace (top) uses round pins, while the Ultegra (bottom) uses rectangular pins. I think both work really well, but then I'm old school. I don't exect them to shift while going up hill out of the saddle.


So what accounts for the weight difference. If the left arms are about the same, then the right side should be about the same, so that leaves the spindle. The Dura-Ace spindle is noticably thinner as you can see. People will say the crank is a good place to save rotational weight, but in this case the extra weigh is in the spindle, where it would be hardly noticed as far as rotational crank weight is. So the extra weight on the Ultegra Crank is more static, than rotational.
Also notice the backside of the spiders. This view really shows the difference between what I call a scallope shape of the Dura-Ace, and Starfish shape of the Ultegra.
So...Is the Dura-Ace worth (about twice) the extra expense?

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