Q Factor of crank vs frame BB width

[marshace]

Understand that q factor of a crank is the horizontal distance between the inside surfaces of the arms at the BB.

Question: does frame dictate what q factor crank you can fit ? or can you fit any crank to any frame using spacers on BB (screw in external BB has spacers, press fit does not) ?

 

Thx

Eric

[Spoke101]

Q-Factor is the horizontal distance between the outside surfaces at the pedals not the BB.

 

If your BB and Crankset is installed properly this distance will remain constant no matter what BB or Frame you use.

 

Type of Frame can dictate Q-Factor where a Frames chain stays are pronounced and clearance becomes an issue between the outside of the chain stay and the inside of the crank arm at the point where the pedals attach.

 

Edit: Q-Factor and Frame type also need to be taken in to account if you are planning on running a Stages power meter.

[koukie]

Q-Factor is the horizontal distance between the outside surfaces at the pedals not the BB.

 

If your BB and Crankset is installed properly this distance will remain constant no matter what BB or Frame you use.

 

Type of Frame can dictate Q-Factor where a Frames chain stays are pronounced and clearance becomes an issue between the outside of the chain stay and the inside of the crank arm at the point where the pedals attach.

 

Edit: Q-Factor and Frame type also need to be taken in to account if you are planning on running a Stages power meter.

Dont you get long spindle and short spindle cranks?

[droo]

Dont you get long spindle and short spindle cranks?

 

Spindle length depends on the BB configuration, Q-factor is a different measurement.

[Spoke101]

Dont you get long spindle and short spindle cranks?

 

Yes you do. But I am referring to the same crankset installed on multiple different bikes.

 

eg:

 

BB30: You get various spindle lengths from different manufactures. Most common are 83mm, 95mm and 101.5mm but the curvature of the crank arm's is different so the Q-Factor remains the same.

http://www.bikerumor.com/wp-content/uploads/2011/12/FSA-SLK-Light-Pressfit-BB30-BB386EVO-comparison02-600x355.jpg

http://www.bikerumor.com/wp-content/uploads/2011/12/FSA-SLK-Light-Pressfit-BB30-BB386EVO-comparison10-600x362.jpg

 

GXP, Shimano, Campagnolo, etc the list goes on and compatibility gets more complex.

[marshace]

Thanks for all the input.