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

New: Vitesse Signal Giveaway's Winner Announced


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
 
1,139
09-01-2024, 03:20 AM
Last Post: Talha
 
9,865
11-07-2011, 07:55 PM
Last Post: Sparkie
 
10,561
04-12-2011, 07:25 PM
Last Post: Dvntie
 
8,639
01-25-2009, 11:25 PM
Last Post: Barry
 
15,701
10-27-2008, 07:42 PM
Last Post: DaveM

Forum Jump:

[-]
10 Latest Posts
The deadliest U.S. counties for cyclists
Today 01:12 AM
WTS New Ariel Rider Grizzly - 52V Dual M...
Yesterday 02:18 PM
What are the best maintenance practices ...
12-24-2024 09:07 PM
MTB Night Lighting - What are recommenda...
12-24-2024 07:59 PM
Cycling industry is pricing out their ow...
12-24-2024 07:37 PM
How many bikes do you have now?
12-24-2024 07:02 PM
Best Phone Mount and Best Headlight
12-24-2024 03:45 PM
Biking with helmet laws
12-24-2024 02:22 PM
(So California) PV Dr to be closed to bi...
12-24-2024 01:51 PM
Speed limiter adjustment
12-23-2024 08:02 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. Alexjohnson
39 posts
no avatar 2. GirishH
20 posts
no avatar 3. Flowrider
12 posts
no avatar 4. JeffAP
9 posts
no avatar 5. Bweighmaster
9 posts