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How much do I tighten a mid-80's Campagnolo Crank Arm 15mm bolt?
- Thread starter Mark McInerney
- Start date
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100bikes
Wore out three sets of tires already!
OK, so I am old school.
Clean the tapers well(Citrus degreaser) , both the spindle and the arm .
Let them dry.
Dry mount.
Tap - read that tap them into position, tighten the bolt with nothing longer than
the peanut butter wrench(6"+-) and tap again.
Tighten and ride.
Precision mounting with these surfaces.
My thought is that lube does just that - lube the surfaces. That works both ways.
Never getting things quite tight and then, letting things loosen up.
Another opinion.
Clean the tapers well(Citrus degreaser) , both the spindle and the arm .
Let them dry.
Dry mount.
Tap - read that tap them into position, tighten the bolt with nothing longer than
the peanut butter wrench(6"+-) and tap again.
Tighten and ride.
Precision mounting with these surfaces.
My thought is that lube does just that - lube the surfaces. That works both ways.
Never getting things quite tight and then, letting things loosen up.
Another opinion.
fattyre
I live for the CABE
Regardless of ones technique, I always try to remove square taper crank arms as little as possible. Every time you tighten cranks down, your smashing them against steel. Can't tell you how many square taper Campy cranks I have seen where the washers or just the bolt bottoms out on the spindle and the cranks still creek when you ride them, greased up or not.
bikemonkey
I live for the CABE
Here is my approach - remove one arm and mark the spindle so you know which way the arm was originally mounted. When replacing the crank arms, mount them the same way they were before you removed them.
Oil or grease cannot be compressed so if you have any lube on the taper (spindle or crank arm), the crank arm does not fit as securely because there can a small degree of "float" and it can work loose later as the grease migrates out under load. I have never had any issues pulling cranks from dry tapers if the extractor threads were good.
However, the crank bolt threads must be lubed and the surface of the bolt head and/or washer as you want minimum friction in order to get the bolt tight and not have a false torque value.
I don't think lube on the tapers will cause the crank arm to move too far up the spindle - that is caused by a wallowed out crank arm that was ridden loose. Everything I can recall in the industry recommended the taper and crank taper be clean and dry.
Of course, that is just me and here are two articles with an opposing opinion.
Jobst Brandt
Jan Heine
Oil or grease cannot be compressed so if you have any lube on the taper (spindle or crank arm), the crank arm does not fit as securely because there can a small degree of "float" and it can work loose later as the grease migrates out under load. I have never had any issues pulling cranks from dry tapers if the extractor threads were good.
However, the crank bolt threads must be lubed and the surface of the bolt head and/or washer as you want minimum friction in order to get the bolt tight and not have a false torque value.
I don't think lube on the tapers will cause the crank arm to move too far up the spindle - that is caused by a wallowed out crank arm that was ridden loose. Everything I can recall in the industry recommended the taper and crank taper be clean and dry.
Of course, that is just me and here are two articles with an opposing opinion.
Jobst Brandt
Jan Heine
Last edited:
bulldog1935
Cruisin' on my Bluebird
as far as grease on the tapers, it should be the thinnest film you can leave behind, and it's just to prevent friction from binding/misaligning the taper during installation.
The actual goal of tightening bolts is to stretch them to 90% of their elastic limit.
Torque is an approximation, and assumes a friction factor of dry threads. If the threads are lubricated, that friction factor changes, and tightening to recommended torque on your torque wrench reading can permanently stretch your bolts beyond their elastic limit and lead to bolt fatigue down the road. Too tight is the same as too loose.
So that is my engineering approach to the problem.
The actual goal of tightening bolts is to stretch them to 90% of their elastic limit.
Torque is an approximation, and assumes a friction factor of dry threads. If the threads are lubricated, that friction factor changes, and tightening to recommended torque on your torque wrench reading can permanently stretch your bolts beyond their elastic limit and lead to bolt fatigue down the road. Too tight is the same as too loose.
So that is my engineering approach to the problem.
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