RobbieTunes

Whitlach beat me to it. Get home and walk in circles.
Glad no injury from the prang.

Someone asked me once if "those old bikes break down?"
" Sure, just like everything else. "

thinktubes 

OldsCOOL

Mr. Spadoni 

scozim 

I instantly thought the same thing.

obrentharris 

Nicely done!
Brent

jlaw

This is part of the reason why highway bridges are inspected at least every 2 years - looks like it could be a fatigue failure - possibly combined with older damage (pedal strike, crash, etc.)

If you inspect the cranks you may or may not see small cracks that are forming. If you have shiny/anodized crank a bit of powdered graphite rubbed onto the crank might help highlight cracks (light-colored baby powder for black cranks). Removing the cranks and using a bright light at a low angle will help.

It's hard to know how much use older components have seen, but it is safe to assume high mileage and try to anticipate problems like this. But there is only so much you can do.

Glad to here no injuries resulted.

Chr0m0ly 

dddd

If this crank has much off-road riding under it's belt, methinks that it's strength/endurance limit was thus overloaded.

I have noted that most off-road cranks seem to have extra metal in this area. I guess that with all of the standing up while passing over trail features that the bending load from the pedal must be typically much higher when riding off road.
And then there is the matter of riding off road, especially with such limited gearing, leading to more in the way of grinding vs. spinning...

And the crank is only 45(?) years old.

I sold a Raleigh to a younger rider who is about 6' and 180, and in 1-1/2 years he's broken now two of the steel cottered cranks at the eye. In each case there was only one hoop fracture, the pedal stayed in place and he continued riding the bike long enough to arrive at my place looking for a replacement.

mixteup

Originally Posted by belacqua View Post

My vintage bike must think it queer
To stop without a farmhouse near
It makes a noise with the front brake
To ask if there is some mistake...

Snow may drift upon the bank,
the MUP is chill, but what’s that clank?
These parts are thirty? maybe more...
Oh Mother-**** that was the crank

[/left][/QUOTE]

Now for sure it's getting dark,
and it's 14 miles to where I park,
so I take out my phone, as I gaze at my bike of vintage perfection -
The screen comes up ........ No connection

merziac

Maybe, the Campys out number the Sugino about 10 to 1, your call.

smontanaro 

Hard to say. Almost every part I have was bought used, so I have no notion of the use it's seen during its lifetime. I think off-road here was just a coincidence. I don't normally do a lot of trail riding, but wanted to see how the new-to-me cx tubulars fared on looser terrain.

79pmooney

Yes, that is the normal mode of failure for a road crank. (And it seems right side cranks break more often than left side.)

What caught my attention is the fact that it is a Sugino, especially a Mighty. I've never heard of a Sugino crank breaking, ever. Not saying it doesn't happen, but this is the first one I've heard about. I've put a few miles on them. Rafced a Mighty in the '70s but it only got 9000 miles when I sold the bike. I rode several pairs into the ground on my fix gear, but replacement was dictated by wear on the arm from winter footware. ( have a box of cranks with 1/3 of the material gone at the ball of my foot.

I have witnessed 3 such failure. 2 on Campy NR cranks of unknown age and vintage and an old Avocet with lots of miles and experience. The Avocet was me. Much like teh OP, I came out of the saddle near the top of a rise and just placed my foot on the road, sat down and came to a clumsy stop,, Then clomped around looking for my pedal until I realized it was strapped to my foot. Got to coast downhill 1 mile to my destination: to hang with the guys, and got a ride on one of their pickups. The two Campys both crashed in races when I was on their wheel. They crashed hard. I snaked through unscathed.

Ben

big chainring 

Bummer. I often am caught in too big a gear coming out of that underpass...stomp up that incline. I have a replacement crank if you'd like it. Very few miles on it....but...its french pedal thread. Ron Boi has taps though.

smontanaro 

Thanks, Paul. I had another Sugino crank in my parts bin. Bike is already back together. My entire family will probably sleep in tomorrow, so I might get in a quick two-legged ride in the morning. Ho, ho, ho!

smontanaro 

A much more typical ride today. Nothing fell apart or fell off. Still more work to do on the bike, but things are moving in the right direction.

Chris Chicago

I broke a sugino triple at the bottom bracket spindle a couple years ago. was standing up at decent speed but not hauling ass, thankfully. thought I was going to control it but landed on my back. Tried to inspect all my cranks after that but not sure it's accomplished anything

Ragel

repechage

repechage

madpogue 

steelbikeguy

glad that you didn't end up getting hurt... it's too easy to think of ways where this could have ended up much worse.

As far as inspections, I have to admit that in this era of sealed bearings, it's easy to let many years pass without pulling things apart and looking at them closely.
Any ideas what a dangerous crack looks like at the pedal eye?? If it is clearly visible under a quick inspection, that's probably a good enough reason to retire it. Do we have a guess whether we can even see a crack that would justify retiring the crank? i.e. should we be using the dye to check for cracks every couple of years, or every 5000 miles, perhaps??

I like to think that I'm pretty easy on parts; i.e. not heavy and not strong, so I generally don't worry about breaking stuff. However, I suspect that Skip isn't any heavier than me, so maybe I need to be more conscious about pulling the cranks off periodically for inspection??

Steve in Peoria

Johno59

I split a DA crank at the spindle end. Fortunately it was steep hill and I was barely moving. Tried to stand with 175mm of busted crank, Look pedal, cleat and road shoe attached to my foot. The whole mess went under the bike and into the rear wheel with my leg attached. Splat. Ached all over - especially my neck. A week later my helmet felt strangely loose. Upon closer examination it had split along the entirety of one side.
The day before the crank retaining bolt had unexpectantly come loose. I simply retightened it and thought none the wiser.