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crank bolt and taper questions - toast?

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crank bolt and taper questions - toast?

Old 06-24-05, 11:44 AM
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crank bolt and taper questions - toast?

Finally have my fixed bike built up. Break my brake trying to install it. Take it out for some practice in a big park at night and put my rear (machine built nashbar) wheel way out of true learning to skid and skip. This gives me more confidence on riding without a front brake for now (Via in Philly wouldn't sell me one without seeing my bike! Not a dis on them, the guy was concerned about selling me junk I couldn't use), at least today, a Quebec holiday when there's not a lot of traffic out.

Also noticed I'd rattled my chainring bolts loose on my skipping endeavor - my fault, I didn't loctite them because I wasn't sure I was going to use this chainring. Do them up, start tightening my crank, and the bolt just doesn't want to stop turning. I managed to push the crank so far down the spindle that the bolts rubbed the chainstay, and I could have kept turning.

Are these cranks toast? They're used campy copy road doubles with a 144 bcd. I was pretty confident that I could just use a shimano bb with them even if it wasn't exactly right (from Sheldon Brown even) unless they happened to be some really weird make (the cranks have no markings on them at all, but look like campy nr without the campy logo), and even then worst case scenario is I ruin the crank, not certain death.

Should crankarms seat all the way so that the spindle of the bb is flush with the taper on the outside of the crank? I didn't think so, but it feels like I could for sure push it that far without much effort. Also, when I go to loosen the crank bolt, it comes free with relative ease, but I still have to muscle it a bit. Zinn says to muscle crankbolts really really hard, but not quite until your veins pop. I guess this is about 350 foot pounds , which I gauge as way harder than I tightened my handlebar bolts, but the just won't get tight. Threads on the crank bolt and bb taper are perfect. Btw, this is with totally ungreased spindles.

I checked out some stuff in the archives, and BostonTrevor seems to be pretty interested in crank bolt issues (have you ever sheared a bolt head off? ), but the links below didn't seem to totally answer my questions, though I will be putting on those crank bolt dustcaps after all re: the latter.

http://www.bikeforums.net/showthread...stalling+crank

http://www.sheldonbrown.com/brandt/i...ng-cranks.html
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Old 06-24-05, 11:47 AM
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you could just need a wider BB. if turning the crank bolt kept pushing the cranks further on it ain't stripped.
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Old 06-24-05, 12:09 PM
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How far into the taper does the crank sit on the spindle then? I'm quite sure the crank on my ss mtb went about 2/3 onto the spindle, but since it works, I don't want to take it apart to find out.

Thanks.
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Old 06-24-05, 12:20 PM
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If the spindle is butting up against the crank bolt you're not going to get them any tighter. and a longer spindle won't do anything.
It sounds like either the cranks don't like the JIS shimano taper and want something wider, or the square hole in the crank arms are flared.
Are you getting this problem on both sides? or just the drive side?
if its on both I'd be more likely to say that its a spindle taper incompatibility problem.

(I think you need some shiny new cranks )
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Old 06-24-05, 12:28 PM
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It's only on the drive side, but you don't know how much I need some shiny new cranks - my left crankarm is a shimano 600 (I was sold the set as 600, and at the time I didn't know the difference). The inside of the crank taper is marked with how far spindles have been inside, about 2/3 of the way).
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Old 06-24-05, 12:40 PM
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I think it turns out I have a really odd crank - I just took it off again, and when I put it back on, it goes further on the spindle than it did before - I can see that I muscled it about 1-2mm further than a perfect chainline.

It was suggested that I might have an Ofmega, Avocet or other weird crank from the 70s with their own proprietary dimensions, with a slightly skinnier taper - I think I do.

I guess it's time to start shopping for cranks a little more seriously now.
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Old 06-24-05, 03:02 PM
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campy cranks require a bottom bracket with a campy-specific spindle. using another axle can damage your cranks.
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