Classic & Vintage - another busted left crank

early 1970s: Agrati steel crank, broke at the spindle and cotter eyes; able to ride home with left pedal timing advanced relative to right.

early 1990s: 1970 Sugino Mighty Compe, broke across the pedal eye during an out-of-saddle climb; ouch!

today: early 1990s Campag. Veloce, crack developing across the end of the spindle eye, parallel to the spindle (pictures to follow)

The Capo once again has an early 1970s Nervar Star crankset, which doesn't look as nice, but at least is much closer to period-correct.

Geez John! You got thunder thighs or what?! Never heard of anybody breaking as many cranks as you do.

yo, john, buddy. Discovery is looking for a replacement rider, I hear. You'd have to ride dura ace, though...

Send me all the rights, my friend...along with the chainwheels...you are under my power... :P

-Kurt

yo, john, buddy. Discovery is looking for a replacement rider, I hear. You'd have to ride dura ace, though...

Chances are, he'll break the integrated BB spindle...

-Kurt

In the early 1970s Jack Disney, a respected southern California velodrome racer with quads, gastrocs, and glutes of steel, broke a Sugino crank and swore off Japanese components. My situation is particularly ironic because I weigh about 143 lbs / 65 kg and consider myself an endurance rider, with "slow twitch" muscles, rather than a power sprinter. My left quad group is 10-20% weaker than my right, the result of a couple of kneecap dislocations. However, I do a fair amount of out-of-saddle climbing, and I love hills.

The Agrati steel crank was on my first 1960 Capo, which was given to me in 1973 by a UCLA physics classmate, a powerful gent of Armenian descent. Lee may well have prestressed the crankset before I ever got hold of it. It did break at its most stressed, weakest point.

The 1970 Sugino Mighty Compe crank was a first-generation product on which I had put close to 40k mi / 65k km, including lots of hill work. I noticed that the next-generation Sugino cranks had an additional mm or two of metal around the pedal eye, so I suspect I was not the only one with a problem.

The real mystery is the Campagnolo Veloce crank, although my son thought he saw some crystallization in the crack, so it may have been a manufacturing defect. I did buy the crankset on eBay, but judging from the almost pristine profile on the chainrings, these cranks had been used very little before I got them. Since the right crank still looks great, I am tempted to look for a replacement left crank and to gamble on it.

I'll match your 3 crankarm failures:

1. 1974: Campagnolo NR, left crankarm, snapped below logo
2. 1988: Shimano Deore DX, left crankarm, crack propagating from spindle hole
3. 1991: Shimano Exage, left crankarm, crack propagating from spindle hole

and raise you one Ultegra cartridge bottom bracket, snapped at left taper, about one week after the 1R let go!

I had a Campagnolo Veloce break at the same place with very little time on it also. The replacement has not given me any grief since.

I broke a left strada crank once - it had a perfect little spherical nodule in the center of the crack (just under the logo). The rep replaced it. I broke a phil bottom bracket once. Phil replaced that one. Said that it was the only one he'd ever seen fail.

John, you're just a manly man and will have to deal with it. Mere cranks cannot stand up to your powers... I know the truth hurts, but that's how it is.

I sheared a Sugino VP (right arm) in two once, right in the middle. However, this was on a bike on which everything broke, including the frame.