Have questions or want to discuss cycling? Join Now or Sign In to participate in the BikeRide community.

New: Take part in the Newton-Rider International Giveaway for a Foldable Bicycle Helmet


Changing 53/39 chainrings to 50/34
#1
I'm looking to change a Shimano 105 53/39 crank/chainring to a 105 (or higher spec) 50/34 chainring. Can anyone please tell me what is involved with this? Do I just need to change the chainrings, or am I going to end up needing to change pretty much the whole drive train? Thanks.
  Reply
#2
A 50T would fit where the 53T is but the 34T won't fit instead of the 39T.
It's to do with the "PCD" (pitch circle diameter) of the chainset.
ie the mounting holes for the rings are on a different radius for the small ring.
You will need change the right crank or change the chainset as a whole.
The chances are your PCD is 130mm whereas you need 110mm for the 50/34 chainrings.

See:-
http://techdocs.shimano.com/media/techdocs/content/cycle/SI/SI_1M30A/SI-1M30A-003-ENG_v1_m56577569830702207.pdf

The other thing you will have to check is if the front dérailleur is also compatible with the smaller ring?
Probably is but some aren't.
Ride hard or ride home alone!
  Reply


Possibly Related Threads...

Forum Jump:

[-]
10 Latest Posts
11-42 cogs on Road bike?
Today 02:04 AM
NewBikeShopper (intro & opinion request)
Today 01:57 AM
1983 Trek 720
Today 12:23 AM
brakes
Yesterday 11:25 PM
Road bike brakes upgrades
Yesterday 01:41 PM
Do you wave to other cyclists?
01-18-2021 02:48 PM
Newton-Rider, a helmet like no other
01-15-2021 05:01 PM
Colnago R41 Handlebar
01-14-2021 10:24 PM
How much do you bike per year?
01-14-2021 04:50 PM
BMX Shoes
01-14-2021 04:42 PM

[-]
Top 5 Posters This Month
no avatar 1. Criminal
20 posts
no avatar 2. RollOn
6 posts
no avatar 3. Henry_G
5 posts
no avatar 4. Yevhen
5 posts
no avatar 5. Zviedrs
4 posts