Creaky crank

[one-eyed_jim]

Are you sure its the crank?

The reason I ask is it may be loose chainring bolts.

... all three of them ...

http://www.lockjawcollars.co.uk/Picture%20051.jpg

 

[cce]

that canti hanger is full of fail also.

 

[MJN]

What cranks and bb are you using,some combinations are prone to creaking.
NEVER grease a square taper bb axle :shock:

 

[oaep7]

Have a go at regreasing the pedal threads - solved a problem I had that drove me nuts for ages, sounded like the cranks but was the pedals.

 

[terryhfs]

I'll fifth that. Never, ever, grease a square taper bottom bracket where it meets the crank. The interface relies on friction to work. If you grease it you'll have to over-tighten it for it to work and that will wear both the crank arm and the spindle very quickly.

 

[one-eyed_jim]

Never, ever, grease a square taper bottom bracket where it meets the crank. The interface relies on friction to work.

I've always greased bottom bracket tapers and haven't had problems - dozens of bikes, hundreds of thousands of miles. The interface relies on geometry and press-fit, not friction. A greased socket turns a bolt as well as a dry one.

http://draco.acs.uci.edu/rbfaq/FAQ/8f.11.html

"Because friction plays no role in torque transmission, preload in the
press fit must be great enough to prevent elastic separation between
the crank and spindle under torque and bending."

 

[MJN]

If you use grease on a bolt thread it actually produces more torque for the same amount of force,this is the same with the crank/bb axle,but what do I know I'm only an engineer by trade.

 

[one-eyed_jim]

If you use grease on a bolt thread it actually produces more torque for the same amount of force,

Don't you mean more tension for the same installation torque?

this is the same with the crank/bb axle,

The crank transmits torque to its axle in much the same way a socket transmits torque to a bolt head. The press-fit is determined by the elasticity of the crank material. Friction in the interface relates installation torque to the press fit you end up with, but doesn't affect the function of the crank in use any more than greasing a socket affects its ability to turn a bolt head.

but what do I know I'm only an engineer by trade.

So is Jobst Brandt, who wrote the rec.bicycles.tech FAQ I quoted.

 

[MJN]

All I know is if you torque a bolt up to the same setting with grease it produces a higher figure on a strain gauge,this also alters with the type of grease used.
Also after previous experiance as a bike shop gimp I wouldn't grease a square taper bb axle after seeing the results.
The result being that the crank is pushed too far onto the taper,just like if you over toqued it dry.
Also after reading Jobst Brandts article he appears to neither confirm the use of grease or not.I can tell you that in heavy industry taper fit items would not normally be greased,the stuff I work with is usually put together dry and removed with heat.
You maybe have different experiances.

 

[terryhfs]

Friction in the interface relates installation torque to the press fit you end up with, but doesn't affect the function of the crank in use any more than greasing a socket affects its ability to turn a bolt head.

Yes, but it's the use of grease during the installation that causes the damage. It allows the crank to be over tightened which damages the taper faces.