[macca22]

I have a Carrera Virtuoso which i am rebuilding. The crank i had on was a 175mm 42/52. I know my arm length needs to remain the same but does the crank have to remain 42/52 or could i use a 39/53? Also the existing bottom bracket is a square tapered type. can i remove and change to a hollowtech or shimano ultegra octolink? Thanks Mark.

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[Anonymous]

Yes you can replace those
Yes you can replace those cranks with modern equipment, and a new BB, with the gearing you want.

Whether you can install a 39t chainring on the existing right crank arm depends on the bolt circle diameter: it would need to be 135mm or smaller to support that size ring. Some older cranks use a 144mm BCD and you cannot fit a 39t ring on them.

http://www.sheldonbrown.com/cribsheet-bcd.html

I am not familiar with your bike but there is a good chance it may have an Italian threaded bottom bracket. Clarify that before buying a new BB.

Posting a photo of your crankset might produce more accurate advice.

[Author]

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