Crank arm fell off
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There are seven main steps to follow when trying to solve a problem. These steps are as follows:
1. Define and Identify the Problem
2. Analyze the Problem
3. Identifying Possible Solutions
4. Selecting the Best Solutions
5. Evaluating Solutions
6. Develop an Action Plan
7. Implement the Solution
I think you did good with the first step.
1. Define and Identify the Problem
2. Analyze the Problem
3. Identifying Possible Solutions
4. Selecting the Best Solutions
5. Evaluating Solutions
6. Develop an Action Plan
7. Implement the Solution
I think you did good with the first step.
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391 Posts
Use a torque wrench to tighten it to spec next time.
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31,676 Posts
Actually no, his crankset is toast. Unless things have changed in the last few years, when a crank falls off a spindle the spindle is toast... And the crank won't stay together again.
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14,713 Posts
Well, often, but not always. And it's not the spindle that is damaged (at least on the square-taper designs I think you're referencing), since the spindle is made of hard steel. The aluminum crank is what gets deformed. But not always irretreviably.
But things actually have changed in the last few years, and there are several different bb designs that work quite differently, and aren't subject to that kind of damage necessarily. I can't tell from the picture what he's got there.
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23,049 Posts
Looks to be splined. And yea, not definitively ruined.
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8,173 Posts
And use some loctite on the threads...
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14,713 Posts
Oh, yeah, I loves me some blue loctite. Especially since I don't have a torque wrench yet (only been riding 40 years or so, so maybe I'll get around to it eventually).
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15,673 Posts
1) loctite? i guess that's why SRAM supplies the cranks w/ tons of grease on the bolt & crank/spindle interface. i've never loc tited any crank bolt, ever. use grease and if you don't have a torque wrench, tighten the sh*t out of it. don't be dainty, they're big bolts.
2) how on earth would ANY spindle be damaged when they're steel and the insert in the crank arm or the crank arm itself is aluminum? how does that happen?
I've been riding for years (15,000 mi+) with a crank arm that occasionally loosens. I just shim it with whatever is around - I've used aluminum foil, plastic from a drink bottle found by the side of the road, and aluminum cut from a can found at the side of the road. I keep a couple of shims in my saddle bag now. A set of shims usually lasts a year or so (well, not the plastic, that didn't last long). Easier than buying a new crank arm.
This is a square taper spindle, don't know if this would work for the splined crank arm in the picture attached by the original poster.
Edit: Oh, and I HAVE torqued the head off a crank arm bolt, so it can be done.
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lol that's not even helpful..
Posted that from my phone this morning.
Whole Story:
No, I didn't crash. I have a hill that's about a 7% grade that I come down on my morning commute. If there are no cars in front of me (no bike lane) I can hit 38 mph. Luckily this happened about halfway to work, 15 minutes after the big hill, as I was crossing an intersection at about 7 mph.
A couple of minutes before this happened I thought that either my cleat was loose on my shoe, or somehow the float adjustment on my pedal had loosened. So I stopped and checked both and they were fine. Never occurred to me that the crank arm could be loose.
The nut takes an 8mm Allen wrench which I don't have on my multi-tool, so I couldn't have done much with out on the trail, and wouldn't have been willing to keep riding unless I tightened it correctly anyways.
Had my support team (i.e. wife,Moho kept reminding me how much she had to do today) pick me up and take me to the LBS.
the spacer that was on there was wrong, so while I waited they fiddled around with it until they found one that was the right size and put it back together.
Took about 20-30 minutes and they wouldn't let me pay.
I've purchased shoes, headlight, tail light, etc from there, but guess where I will be purchasing all of my future stuff from?
Whole Story:
No, I didn't crash. I have a hill that's about a 7% grade that I come down on my morning commute. If there are no cars in front of me (no bike lane) I can hit 38 mph. Luckily this happened about halfway to work, 15 minutes after the big hill, as I was crossing an intersection at about 7 mph.
A couple of minutes before this happened I thought that either my cleat was loose on my shoe, or somehow the float adjustment on my pedal had loosened. So I stopped and checked both and they were fine. Never occurred to me that the crank arm could be loose.
The nut takes an 8mm Allen wrench which I don't have on my multi-tool, so I couldn't have done much with out on the trail, and wouldn't have been willing to keep riding unless I tightened it correctly anyways.
Had my support team (i.e. wife,Moho kept reminding me how much she had to do today) pick me up and take me to the LBS.
the spacer that was on there was wrong, so while I waited they fiddled around with it until they found one that was the right size and put it back together.
Took about 20-30 minutes and they wouldn't let me pay.
I've purchased shoes, headlight, tail light, etc from there, but guess where I will be purchasing all of my future stuff from?
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580 Posts
Sounds like you got real luck on this one. In the right situation things could have been ugly. Great bike shop to get it fixed and asked for no payment. Great LBS to fix it no cost. Sounds like they know how to get and keep customers. Just proves a pre ride once over is worth the time. Glad you did not get hurt
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507 Posts
Go on YouTube and look up SRAM-Tec. There is a SRAM provided video that will show you how to properly lubricate, install, and tighten the crank set. As long as the spline slots on the crankarm are not all wonked it should be an easy fix.
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