Thursday, June 16, 2011

Cracked Crank Cutting Corner.....

...and could have creamed calf.

(Note: This chronologically an old post, that I am just finishing up)

I generally avoid heavy alliteration, and the above is why. It can lead down an annoying black hole of sacrificing meaning and content for form and style. In other words, it can suck.

But I had a story to tell about a chain ring, a cracked crank, some pedals and I just got carried away.

First some background:

For a very long time ( 5 years or so), my crank set has been a Dura-Ace FC-7703 triple. A nice set by any standards. For most of that time, the pedals were Crank Bros. Quattros. I have been riding on the original chain rings all that time too. My best guesstimate is between 15K and 20K miles on those, maybe a little less on the Quattros, for a variety of reasons.

I did not buy the Dura-Ace because of its low weight, although it is very light. I don't race and a few extra grams mean nothing to me. Not really concerned about labels either, but I have to mention it or the story is incomplete. I bought it for durability and craftsmanship. I appreciate craftsmanship. And boobs.



Well, the chain rings wore out and I broke a crank arm.

Not at the same time of course.

No, I was suffering with the worn chain rings, both the middle and the outer , which was causing nasty chain behaviour, especially in the climbs. Now, if you recall, this is a triple set, and apparently the middle ring on this set is used nowhere else on the planet. A chain ring, like brake pads, it not something you buy used, unless you are absolutely sure it has virtually no miles on it. So I had to buy new, I had to buy Dura-Ace and the middle ring in particular is a rare part so not a lot of them sitting around ( remember supply and demand?). Bottom line: It was expensive. I had certainly gotten the miles out of them, and it was necessary, so I bit the bullet and ordered a pair of rings.

However, before the new rings arrived, my massive power eventually did the inevitable-I broke a crankarm:











The ferocious physics of force. Minus acceleration, mass is meaningless ( succumbing again to the sweet sirens song of alliteration)

More Background:


  • The left crank on the FC-7703 triple is identical to the left on the FC-7701 double.

  • It's easier to find parts for the double, and , in fact, a whole barely used double ( left and right), including fresh double chainrings can be found for about the cost of the one middle triple chainring, and much less than both middle and outer triple chainring.

  • I would gladly ride a double. I rarely use the granny gear ( although when I do, its a very guilty pleasure)

So, I ending up buying a near perfect double, including both chainrings ( in a better ratio than I currently have, for how I ride) for less than I had just paid for the new chainrings for my triple. But I was stuck with both. Its all about the timing.


Tech savvy readers may note that the bottom bracket would also be different. Lets say, for the sake of argument, that I had a normal Q-Factor. Well, it just so happens that I have a perfect double sized bottom bracket jsut laying around. However, I am larger than most mere mortals, moreso in the pelvis area, so a wider bottom bracket on a double may have been just the ticket for addtional comfort and power...

-Evil C.

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