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Thirty years of wrenching and I just now figured out I was overtorquing pedal threads on alloy cranks back in the '90s because a customer brought in a cracked crank arm and asked if I'd seen that before.
He was a big dude on a mountain bike and he showed me the fracture line starting right where I'd cranked down too hard with a standard pedal wrench, no torque wrench, and I wonder how many other parts I sent out the door with hairline cracks back then, has anyone else had a similar wake-up call with something that seems simple?
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olivia_moore17d ago
Gotta call out something here - those old standard pedal wrenches didn't really let you overtorque that easily on purpose. Most of us back then just tightened until it felt snug and gave it a little grunt. The real issue with alloy cranks from the 90s was the cheap metal they used, not so much the torque. I've seen plenty of those cranks crack even with a careful hand. It's more about the material quality than how hard you leaned on the wrench.
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margareto2617d agoMost Upvoted
Haven't we all had that moment where you find a crack in a crank arm and just know it wasn't from overtightening? I've pulled apart a few sets from that era, and the metal grain looks like cheap sand castings. You can literally see the porosity in the metal if you look close enough. I always tell new riders that if you're touching up a steel crank, go by feel. But with those old alloy ones, maybe even a torque wrench can't save you if the metal's bad from the start.
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robin62816d agoTop Commenter
Wait, you're saying those old wrenches actually had a built-in limit? I never knew that. I always thought they were just a plain piece of stamped steel. That changes a lot about how I look at those old builds. I've gone through several sets of those 90s alloy cranks and always blamed my own heavy hand for the cracks. Now you're telling me the metal itself was the problem from the start. I'm honestly surprised I didn't snap more of them off, given how many I must have overtightened without realizing it.
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