CannonD M400 Crank Upgrade
01-17-20, 01:49 PM
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CannonD M400 Crank Upgrade
Ok so I have this very nice vintage M400 8 speed bike with a worn out CPI chainring, am replacing it with shimano altus FC-m311 question is whether I can keep my bottom bracket I am getting some info I will need to replace with a longer one 123mm vs 110 it already has ?? Can somebody comment on this..............thx.
01-17-20, 02:04 PM
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Can't you just replace the ring?
01-17-20, 02:16 PM
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Yes but it's SO cheap for vintage parts, why bother? Plus the new one has a bashguard all for $30 SHIPPED!! 2 Chainrings are shark-toothed CPI is OOB, Plus 20 year old crankarms make me nervous.....
01-17-20, 02:36 PM
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Depends on the recommended BB spindle length for the Altus cranks.
The arms will certainly fit on the spindle tapers, but if the BB is 10mm too short you might wind up with the chainrings hitting the chainstay.
You can possibly estimate any requirement for different BB length by examining the geometry of the arms and square tapered hole - if the end of the arm is significantly further away from the spindle hole, as measured parallel to the spindle, then it probably needs a new BB. If the spindle hole and pedal hole are a similar distance, as measured parallel to the spindle, then it could be fine without changing anything.
On second thought - I just googled FC-M311 and found a technical doc from Shimano recommending a 123mm BB.
https://si.shimano.com/pdfs/si/SI-0094A-001-ENG.pdf
Sorry, friend, but you need a new BB.
The arms will certainly fit on the spindle tapers, but if the BB is 10mm too short you might wind up with the chainrings hitting the chainstay.
You can possibly estimate any requirement for different BB length by examining the geometry of the arms and square tapered hole - if the end of the arm is significantly further away from the spindle hole, as measured parallel to the spindle, then it probably needs a new BB. If the spindle hole and pedal hole are a similar distance, as measured parallel to the spindle, then it could be fine without changing anything.
On second thought - I just googled FC-M311 and found a technical doc from Shimano recommending a 123mm BB.
https://si.shimano.com/pdfs/si/SI-0094A-001-ENG.pdf
Sorry, friend, but you need a new BB.
01-17-20, 03:44 PM
#5
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BB spindle length is determined by crankset, not bike. So yes you will need a longer one.
i have bikes with crank arms as much as 60 years old, so I don’t fear old arms. Taperswire out? Rings worn out? You bet, replacement is logical.
i have bikes with crank arms as much as 60 years old, so I don’t fear old arms. Taperswire out? Rings worn out? You bet, replacement is logical.
