New: Take part in the January 2020 BikeRide Giveaway for a HEDKAYSE | ONE bike helmet

Welcome guest! Register or sign in to participate in the cycling discussions.


How to choose the right bottom bracket?
#1
Hello everyone,

I am custom building my own bike, basically I am building a bike from scratch. I've got the frame and I have measured the shell width which is 68mm. I have bought a single speed 44 Tooth chainset/crankset. Now how do I know which size bottom bracket would fit the crankset? Would I have to buy 3 or 4 different size bottom brackets and try each one out to get the right bottom bracket? Somebody please help.

Thank you
Ibs
  Reply
#2
(08-25-2013, 05:38 PM)ibie1983 Wrote:  Hello everyone,

I am custom building my own bike, basically I am building a bike from scratch. I've got the frame and I have measured the shell width which is 68mm. I have bought a single speed 44 Tooth chainset/crankset. Now how do I know which size bottom bracket would fit the crankset? Would I have to buy 3 or 4 different size bottom brackets and try each one out to get the right bottom bracket? Somebody please help.

Thank you
Ibs
generally the BB width is spec'd by the crankset, this would only be bad if you are doing something freaky with the rear hub. some BB's are adjustable to 2 or 3mm. If everything is normal check the specs on your crankset and go with that first
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
  Reply
#3
Thank you for your reply. I bought the crankset on ebay and it doesn't specify anything on it. All it reads on the crank arm is RC-170-5.
  Reply
#4
(08-25-2013, 07:53 PM)ibie1983 Wrote:  Thank you for your reply. I bought the crankset on ebay and it doesn't specify anything on it. All it reads on the crank arm is RC-170-5.
try to pull the ad up again and send it to me, or find the seller and he may have more than one. it may have said in his post and u did not catch it. Try to find the brand name and model. It may have claimed a chainline dimension too to work from. Keep digging
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
  Reply
#5
Somehow you need to get a baseline measurement with the crank mounted from the chainring center line to the bike center line. And the same information for your rear wheel. Then knowing the length of the BB you used for the measurement, through arithmetic, figure out the length of the BB you need. Your measurement can be made with any BB on any bike, as long as you know be measurement the BB that you are using for measurement - and the new crankset will fit.

Ref: http://sheldonbrown.com/chainline.html
Nigel
  Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  Road cranks in 86mm bottom bracket 8F1EFD2553144920BDA6 1 340 08-22-2019, 09:44 AM
Last Post: Papa Dom
  Bottom bracket... Strange style I haven't seen before? Quixoticish 2 5,015 08-06-2017, 01:37 AM
Last Post: condor
  BMX Bottom Bracket Creaking and Clicking felpel102 2 6,908 10-15-2016, 08:36 PM
Last Post: GeorgeET
  Clicking noise/feeling from bottom bracket/pedals/chain? saashi 2 8,411 01-08-2016, 05:08 AM
Last Post: ajstevo
  No spindle in the bottom bracket? Jacomo 5 5,994 09-18-2015, 11:11 AM
Last Post: Painkiller
  Shimano BB-UN26 bottom bracket torque specs Tranced 5 9,857 09-13-2015, 05:33 PM
Last Post: DaveM
  Help to identify and upgrade Huffy BB bottom bracket rpesq 3 8,753 09-04-2015, 04:35 PM
Last Post: DaveM
  Bottom Bracket removal a failure. Two new Kuwahara's. Pics up now. elmore leonard 0 368 05-15-2015, 12:41 AM
Last Post: elmore leonard
  Frozen bottom bracket on Katmando? elmore leonard 8 7,787 05-12-2015, 11:28 PM
Last Post: elmore leonard
  Crank bearing bottom bracket edge 4 6,807 05-08-2015, 10:56 PM
Last Post: edge

Forum Jump: