Help me understand bottom brackets and cranks

Question

I have a Norco Threshold cyclocross bike (http://www.norco.com/bikes/road/cyclocross/threshold-carbon/threshold-sl-ultegra/) . It has a PF30 bottom bracket and an FSA Energy Cross PF30 46/36T crank.

The BB is making a lot of clicking and creaking noises, and if this cannot be fixed, I am thinking about replacing the bottom bracket with a Praxis Conversion BB (http://www.praxiscycles.com/conversion-bb/). That BB is designed to replace a PF30 BB. It is supposed to work with "Shimano™ Hollowtech II steel spindle road cranks only". Praxis also offers variants of the same Conversion BB for Shimano Mountain, SRAM road/mountain, Campagnolo. I assume I can ignore the Campagnolo variant.

I am trying to figure out if it will work with my existing FSA Energy Cross crank. I am unable to tell what the difference is between various types of cranks. A lot of websites talk about "24mm standard" but I have no idea what that means. Is it the same as Shimano Hollowtech 2 ? What characteristics must be the same for two cranks to be compatible ? Diameter, Length, something else ?

This is the crank: http://www.fullspeedahead.com/products/cranksets-cyclocross/energy-cyclocross-crankset-4636-bb30/ On the page, it says "BB30", but it also has a "PF30" logo. Does that mean it works with both types of bottom brackets ?

Answer 1

24mm refers to the diameter of your spindle (the rod connecting the two cranks)

You can look for more details on this chart: http://www.competitivecyclist.com/images/sizing/FSA___RD_CRANKSET_STANDARD_18x24_20140306_reduced_size.jpg

Hope this works for you :-)

Answer 2

I wonder if replacing the bottom bracket will fix the noise. This does not address your technical questions, but might be helpful.

Creaking and clicking can come from several places.

The pedal itself can creak/click. Check the pedal for anything loose.

The pedal/crank arm interface can also. I recommend a bit of grease on the threads. It is a steel/aluminum interface, and these will corrode with time. ( chemistry ).

The crank arm/spindle interface can be noisy. All I have seen is that you do not grease here, even if it is steel/aluminum, you can pull the arm on too far and deform the crank arm over time. It is a press fit.

The bottom bracket to bottom bracket shell can creak. Frame materials, bottom bracket retaining method and materials and thread depth are factors. I recall a bike with a sealed bottom bracket and aluminum retaining rings in an aluminum frame. I could not get it to stop clicking, but I did not have much time with it.

The bottom bracket bearings can make noise. Check if the spindle rotates well. If you feel unsmoothness while rotating it, that might be an issue.

Almost forgot. The spokes in the rear ( driven ) wheel can click. They can notch into each other and if high "winding" load is put on them, the hub twists a bit in relation to the rim and can pull out of the notch a bit, to click when it goes back in. You would have to have an oldish wheel and a lot of power to make this happen.