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I have an old French road bike, 1966 era, with a Zeus bottom bracket with square-tapered spindle. I recently disassembled the bike to have the frame powder coated. Since re-assembly, it seems that the crank bolts keep loosening after only an hour's worth of riding.

I finally checked with a torque wrench and found them to be way too loose. I have since torqued them to 30 foot pounds as seems to be the mid range of torque value for most older cranks.

Now, some suggest NOT checking bolt torque repeatedly as this will result in repeated re-torquing, shoving the crank further up the spindle taper, eventually resulting in crank-arm cracking and failure. Others suggest repeated checks every hundred miles or so, re-torquing as needed.

I should mention that I greased the spindle taper before crank-arm installation as well as the bolts themselves.

Thoughts? Suggestions?

Assistance is greatly appreciated. Thanks!!
 

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Retorquing will not press the crank further onto the arm if the similar torque values are used each time. The correct way to torque the bolt is to LOOSEN it first, then tighten to the target value. Usually, once a crank is bedded in, it needs no further torquing. Perhaps due to your crank's age it's already flared oversized and near the end of its life, which is very common with aluminum, square taper cranks.

To grease or not to grease crankarms is one of the great debates. I say no, because a dry interface there will not seize or creak. Greasing the interface will enable the arm to press fit further onto the axle with more ease, increasing the likelihood of flaring.
 

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I have an old French road bike, 1966 era, with a Zeus bottom bracket with square-tapered spindle. I recently disassembled the bike to have the frame powder coated. Since re-assembly, it seems that the crank bolts keep loosening after only an hour's worth of riding.

I finally checked with a torque wrench and found them to be way too loose. I have since torqued them to 30 foot pounds as seems to be the mid range of torque value for most older cranks.

Now, some suggest NOT checking bolt torque repeatedly as this will result in repeated re-torquing, shoving the crank further up the spindle taper, eventually resulting in crank-arm cracking and failure. Others suggest repeated checks every hundred miles or so, re-torquing as needed.

I should mention that I greased the spindle taper before crank-arm installation as well as the bolts themselves.

Thoughts? Suggestions?
Back in the day it was standard practice to install the cranks and then give them another tug after 100 miles. After that you typically didn't need to tighten them again. If you have in any way damaged your cranks by riding them loose you may be carrying a crank tool with you at all times (lte's hope not). The argument to not grease the crank axle tapers is a relatively new one. Back when your bike was built everybody greased the tapers. I understand the arguments. I always grease mine and have never had an issue in over 300,000 miles of riding square taper cranks. YMMV.
 
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