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


Gearing Question
#1
Hi Alex, cool stuff. quick question:
I have a road bike with Shimano 105 double chainring cranks 53/39 and Sram 9speed 12-13-14-15-17-19-21-23-26. I'm thinking of doing a hilly century and some suggested I change the small chainring 39 to a smaller 30t (available for triple cranks) and then replace the 12t, 14t & 26t cogs of the rear cassette with 25t, 27t & 30t... is that really practical? or do-able at all?
Thanks!
Jason

  Reply
#2
Hi Jason,
Thanks for your comments and great question. I must admit that one of my weaknesses is calculating gear ratios, and I don't want to give you weak advice, so I have to suggest that you post your question in the following forums:<br />
http://www.bikeforums.net/forumdisplay.php?f=10
It's the best place I know of to get technical advice from the many participating bicycle experts.

  Reply
#3
Alex, thanks for getting back to me, and fast!
Well, let me re-phrase my question, forget about gear ratios, that's hard for any expert to answer because it depends on how strong the rider is, the steepness/grade, head wind, distance rode, etc... Let's just assume that I'm trying to experiment with certain range of chainrings and cassettes, my question for you is:
Is it mechanically possible to modify my current setup of (shimano105 double chainring cranks 53/39 and sram 9speed 12-13-14-15-17-19-21-23-26) to:
1)53/30; 13-15-17-19-21-23-25-27-30<br />
- or -<br />
2)55/30; 13-14-15-16-17-19-21-24-28
I don't wanna buy the parts and then find out later that, the front chainring range of 55t to 30t doesn't fit in the front derailer - too large of a jump? Having a 30t at the rear cassette would require a change of the rear derailer to something that has a longer cage, so that the pulley have enough clearance for the 30t?
I've also heard something about BCD sizing of the chainring/cranks that might make my suggested modification impossible? i thought you might have a better idea of what BCD means and how it'd affect the modifications i had in mind. given these limitations, can you suggest something that'd work and yet closest to what i have in mind?
Thanks,<br />
J

  Reply
#4
Sheldon posted a whole archive of helpful information on gearing here:
http://www.sheldonbrown.com/gears/
Hope that helps!

  Reply


Possibly Related Threads...
Thread
Author
Replies
Views
Last Post
 
1,525
09-01-2024, 03:20 AM
Last Post: Talha
 
10,266
11-07-2011, 07:55 PM
Last Post: Sparkie
 
11,016
04-12-2011, 07:25 PM
Last Post: Dvntie
 
8,901
01-25-2009, 11:25 PM
Last Post: Barry
 
16,232
10-27-2008, 07:42 PM
Last Post: DaveM

Forum Jump:

[-]
10 Latest Posts
braking by reversing the pedals
Today 07:04 PM
Post-Ride Nutrition
Today 02:06 AM
🚴‍♂️ Saddle Up for the Belgian Waffle Ri...
Today 02:03 AM
Pre Ride Food Intake
Today 12:14 AM
SAVA Explorer 6061?
Yesterday 03:31 PM
Zwift v Spin v Wahoo
04-01-2025 05:59 PM
Have you Ever Tried an Electric Bike?
04-01-2025 05:07 PM
Good Morning from SW Ohio
04-01-2025 07:32 AM
(So California) PV Dr to be closed to bi...
03-31-2025 09:14 PM
Tubeless vs. tubes: What are the pros an...
03-31-2025 08:28 AM

[-]
Join BikeRide on Strava
Feel free to join if you are on Strava: www.strava.com/clubs/bikeridecom

[-]
Top 5 Posters This Month
no avatar 1. GirishH
22 posts
no avatar 2. Flowrider
18 posts
no avatar 3. meamoantonio
12 posts
no avatar 4. Jake1
11 posts
no avatar 5. SPINMAN
8 posts