Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-17-11, 04:30 AM   #1
maiello
Senior Member
Thread Starter
 
Join Date: Jun 2011
Location: Bedfordshire, England
Bikes: Peugeot (753r frame-1989), Raleigh (Reynolds 653-1991).
Posts: 72
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
gear ratios, what's the difference

Quick question, as I'm quite numerically challenged, is there much difference between a 40:28 gearing which gives a ratio of 1:43 (10:7) and a 34:25 gearing which gives a ratio of 1:36 (34:35) in real terms when climbing. Any thoughts?
maiello is offline   Reply With Quote
Old 07-17-11, 05:34 AM   #2
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 28,847
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 66 Post(s)
The 34x25 gear is 5% lower than the 40x28 (1.36/1.43=0.95) so it will require 5% less pedal pressure but 5% higher cadence to maintain the same climbing speed. I think it would be a slight but noticable difference.
HillRider is offline   Reply With Quote
Old 07-17-11, 09:37 AM   #3
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 29,660
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 217 Post(s)
A 5% or so difference at the low end isn't that noticeable if the higher one is low enough, but will give you a bit more breathing room when you need it.

Most road bikes are set up with 5-7% jumps toward the high end giving you the ability to fine tune your cadence and pedal effort where you do most of the riding. But as we move toward the low end the jumps are usually closer to 10%, since in those gears cadence isn't the issue, just leverage and torque.

So figure the 5% difference as being about 1/2 of a typical low end gear step.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline   Reply With Quote
Old 07-17-11, 11:34 AM   #4
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 19,614
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 432 Post(s)
Yea, you want to use the 34/28, rather than the 40/28..

easier to compare things that only have 1 variable.

rather than 2 ..
fietsbob is offline   Reply With Quote
Old 07-17-11, 02:16 PM   #5
maiello
Senior Member
Thread Starter
 
Join Date: Jun 2011
Location: Bedfordshire, England
Bikes: Peugeot (753r frame-1989), Raleigh (Reynolds 653-1991).
Posts: 72
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Many thanks. Makes much more sense.
maiello is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 12:56 AM.