Sugino XD600 Loose
09-23-15, 08:18 AM
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Sugino XD600 Loose
I put this crankset on my commuter and today the left crank started loose. The BB is Shimano UN55 (?) 115mm, and both should be JIS. Its been fine for a month or so of occasional commuting.
Did I just not tighten it down enough before? I did have my foot a little more outboard because my heel was nipping my kickstand, so I think this is what started it.
Did I just not tighten it down enough before? I did have my foot a little more outboard because my heel was nipping my kickstand, so I think this is what started it.
09-23-15, 08:23 AM
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It probably just needs to be tightened down. Don't overdo it but it looks like you underdid it. I ran into a bike mechanic on a tour who told me that square taper cranksets are prone to failure. I don't think that's true but it's clear that a lot of people tighten them down properly.
Be careful; if you run that crank arm loose, you're likely to ruin it.
Be careful; if you run that crank arm loose, you're likely to ruin it.
09-23-15, 08:31 AM
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The recommended tightening torque for square taper cranks (350 to 450 inch-pounds) is a LOT tighter than most new mechanics realize and far more than a typical 8 mm allen key can provide. A hex bit in a torque wrench is really recommended. Assuming you didn't torque it properly you were on borrowed time and it picked now to finally come loose.
As noted, if you rode with the arm loose for any real distance you may have distorted the arm's square hole and it will never be right again.
As noted, if you rode with the arm loose for any real distance you may have distorted the arm's square hole and it will never be right again.
09-23-15, 08:50 AM
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Every amateur mechanic has undertightened a square taper crank at some point. In my experience (yes, I did it too...) once you feel it loose the arm is ruined and needs to be replaced. It only takes a little movement to ruin the tapers. Your best bet now is to re-install it with as much force as you possibly can and start shopping for a new crankset.
For a much better and detailed explanation, see here: Installing Cranks by Jobst Brandt
That mechanic was wrong, but lots of cranks do get ruined from undertightening. Installed properly, a square taper crank will be good forever or until the bottom bracket needs servicing/replacement.
For a much better and detailed explanation, see here: Installing Cranks by Jobst Brandt
That mechanic was wrong, but lots of cranks do get ruined from undertightening. Installed properly, a square taper crank will be good forever or until the bottom bracket needs servicing/replacement.
09-23-15, 09:04 AM
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It probably just needs to be tightened down. Don't overdo it but it looks like you underdid it. I ran into a bike mechanic on a tour who told me that square taper cranksets are prone to failure. I don't think that's true but it's clear that a lot of people tighten them down properly.
Be careful; if you run that crank arm loose, you're likely to ruin it.
Be careful; if you run that crank arm loose, you're likely to ruin it.
When I used square taper, I always torqued my bolts to the same torque as HillRider suggests. I never had problems with an arm coming loose. But I've seen many poorly torqued and ruined square taper cranks. Even a moderate amount of riding on a loose crank will ruin it.
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Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
09-23-15, 09:06 AM
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Always use a torque wrench on a square taper.
Learned that the hard way.
Learned that the hard way.
