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Discussion Starter · #1 ·
Hey all....

Just managed to get my "new" bike together... a frankenstein monster of an old steel frame with rattle-can paint job, some new parts and some parts pillaged from my Cannondale. Everything went together beautifully, especially since this was my first journey into bike-building and "tweaking." Even had a couple guys at the bike shop compliment me on the paint. I'll post photos when I get 'em developed.

One problem. One of the new parts was a spankin' new Shimano crankset. Well, the non-drive side crank bolt will NOT stay put! I wrench the bolt down tight, and within 500 yards of riding, it has loosened to the point where I can feel the crank move slightly with every stroke.

I thought the bolts were threaded so that the cranking action actually kept them tight, but this is frustrating. I don't want to have to stop every 2 miles and tighten the friggin bolt.

Any thoughts on how to keep this bolt tight?
 

· Resident Curmudgeon
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A couple of thoughts. It's not unusual to have a crank arm come loose, especially after an install. You may have to tighten it several times.

You could try some Loctite on the crank bolt.
 

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Everyone's advice is right on. But your "I feel the crank move" makes me think that your crank may not be properly seated on the spindle. Remove the crank and reinstall. If you still feel the crank move, the crank-spindle mating surfaces were deformed and the crank is toast. Don't ride another yard until you remove and reinstall. I'm guessing this is a 9-speed Octalink crankset.
 

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They have different "grips" of Loctite. The different adhesion comes in different colors, red, blue, etc. Some lock tight, some only prevent vibration. Another suggestion is to buy either a toothed washer or a flat "pressure spring" washer, not a lock washer. This is a washer that is dished and as you tighten down, it flattens.
 

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Discussion Starter · #7 ·
Yes, bolt tightened to correct torque.

Once again, thanks for all the advice. I'll pull the crank and make sure it is seated correctly. If I still have problems I'll use a bit of locktight.
 

· Resident Curmudgeon
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Lawrence is right about loctite. It comes in different strengths, which are denoted by colors. I don't know what all of them are. I do know that if you use the strongest one, you'll have to use a welding torch to get the pieces apart. Probably not something you'd prefer to do on your expensive cranks. The lowest or 2nd lowest bonding strength would be my choice.
 

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ditto, use the blue...

stuff. I had the same exact problem, used a bit of blue locktite, no more problem. And, I was able to get it off later, but you may want to use a stronger tool than an allen wrench to break the seal, if that is what your crankbolt requires.
 

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Discussion Starter · #12 ·
I took it a step further and removed the bottom bracket. Greased the threads, used some plumbers tape (which I didn't do originally). Reinstalled cranks with some plumber's tape and we'll see how it goes. If this doesn't work, THEN I'll get some locktite (blue!)

Thanks again!
 

· 100% torqued
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The few times I have seen octalink BB/cranks loosen the crankarm splines were ruined on the initial install. Remove the self estractor before you installed them? If not it is hard to line the splines up correctly. I would bet this is the cause from the symptoms you describe.
 

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OP, IS this an octalink crankset or one of the 7800 style external cup cranksets? Cause if it's external then that crank bolt is only to tighten the crankarm up to the cups, the hex bolts on the side of the left crank arm are what hold the thing on.

(I know, I know, pretty small chance that this is the problem, but thought I'd mention it.:) )
 

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Discussion Starter · #15 ·
My crankset is Shimano Tiagra FC-4401 52/39T Double Road Crankset and the Shimano BB-6500 - Ultegra Bottom Bracket. So it is octalink.

Howzit.... not sure what you mean by "remove the self estractor" ??

I looked at the crankarm splines and everything seemed fine... no damage. So I put it all back together and rode into work this morning. No looseness that I can tell.
 

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Discussion Starter · #16 ·
Well, I went on a couple rides this weekend. 25-miles on Saturday (solo) and 45-miles on Sunday including a 1,100 climb over Gates Pass here in Tucson. Crank felt funny on occasion, but not constantly. At one point, when we were taking a break, I leveled the cranks with the left crank forward. I leaned over the bike and put my hands on the pedals, then pushed down on the left side, holding the right steady.... and I felt the left crank shift slightly. So something is wrong.

I took the bike into the shop after the ride. I hope I haven't stripped out the splines on teh brand-friggin-new crank (and/or bottom bracket).
 

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The crank arm is toast. Once they come loose once, they wear just enough that they'll keep coming loose. The taper fit is easily damaged and it would take a good machinst with precsion tools to be able to measure the damage. Octalink actually uses a taper fit to hold the crank arm to the BB axle. The splines are only for locating the arms correctly.

The self-extractor is the ring around the allen bolt head. It has two holes in it. You should have gotten a small black wrench-like tool with the cranks. It's for removing the self-extractor rings. You should remove the self-extractors when putting the crank on, and look carefully at the crank/BB interface when you slide the crank on the BB to make sure that the BB's splines line up with the slots in the crank arm. If you don't remove the self-extractor rings so you can look, it is possible to get the cranks misaligned. If you do that then the arms won't seat fully on the BB and you will probably ruin them by driving them into the splines.
 

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Discussion Starter · #18 ·
Well, I never received any little tool with the crankset... that is interesting. Anyway, figured the crank was shot. Thanks for the help, Eric. I'll have to see how much $$$ in damage I caused when the shop calls me.

Live and learn, I guess, eh?
 
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