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


Go Back   > >

Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

User Tag List

Reply
 
Thread Tools Search this Thread
Old 08-20-09, 07:21 PM   #1
corinthincamo
Newbie
Thread Starter
 
Join Date: Jan 2008
Bikes:
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Cyclocross gear ratio question

If 34/15 is similar in ratio to 42/18. What if any draw backs would there be to running a smaller chainring and cog. Are there measurable efficiency gains either way?
corinthincamo is offline   Reply With Quote
Old 08-20-09, 07:57 PM   #2
Tomo_Ishi
Riding Engineer
 
Tomo_Ishi's Avatar
 
Join Date: Jan 2008
Location: Tokyo
Bikes: Kiyo Kiyo Kiyo
Posts: 836
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I think you are better off with 42/18. I think 15T might be too small and chain might skip. Sheldon Brown said gears and chains are less strained with big gears (given same gear ratio), too. (Go to http://sheldonbrown.com/singlespeed.html and look for an entry under "Big or Small?"

He also said clearance could become a problem, though. You should check in with Cyclocross forum to find out about the clearance you need.

Tomo_Ishi is offline   Reply With Quote
Old 08-20-09, 09:08 PM   #3
queerpunk
aka mattio
 
queerpunk's Avatar
 
Join Date: May 2005
Bikes:
Posts: 5,960
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
i too have heard from trackies that larger chainring/cog combinations are more efficient.

i saw the title of the thread and was gonna chime in and say "i rode 42x18 for a few cross races and it was good."

'course if you don't want to spend money on a new cog and cr, you could just do the 34 15 or whatever you've got.
queerpunk is offline   Reply With Quote
Old 08-20-09, 09:53 PM   #4
wearyourtruth
Ride for Life
 
wearyourtruth's Avatar
 
Join Date: Jun 2004
Location: Baltimore
Bikes:
Posts: 2,729
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
the reason a smaller chainring/cog combo is beneficial for cyclocross is the clearance of the chainring. a cyclocross frame is already designed with a higher BB for this. it's simple... the smaller your chainring, the taller the obstacle you can roll over without trouble.

it is true what has been said about chain wear though. a 15t will wear your chain out a little faster than an 18t.

as for efficiency, it's pretty much identical.
wearyourtruth is offline   Reply With Quote
Old 08-21-09, 11:02 AM   #5
Cynikal
Team Beer
 
Cynikal's Avatar
 
Join Date: Apr 2004
Location: Sacramento CA
Bikes: Too Many
Posts: 5,920
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
I run a 38x17 with is about the same. It's what I had in the parts bin and works. SS CX kick a$$.
Cynikal is offline   Reply With Quote
Old 08-21-09, 01:18 PM   #6
mihlbach
Senior Member
 
mihlbach's Avatar
 
Join Date: Dec 2005
Location: Long Island, NY
Bikes:
Posts: 6,400
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Tomo_Ishi View Post
I think you are better off with 42/18. I think 15T might be too small and chain might skip.
This is nonsense.


Quote:
Originally Posted by wearyourtruth View Post
the reason a smaller chainring/cog combo is beneficial for cyclocross is the clearance of the chainring. a cyclocross frame is already designed with a higher BB for this. it's simple... the smaller your chainring, the taller the obstacle you can roll over without trouble.

it is true what has been said about chain wear though. a 15t will wear your chain out a little faster than an 18t.

as for efficiency, it's pretty much identical.
A+
mihlbach is offline   Reply With Quote
Old 08-23-09, 09:23 AM   #7
corinthincamo
Newbie
Thread Starter
 
Join Date: Jan 2008
Bikes:
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Great info. I am going to run 34/15 see how things go. I'll report back with my opinions once cross season gets under way. Thans
corinthincamo is offline   Reply With Quote
Old 08-23-09, 10:03 AM   #8
Dion Rides
Guest
 
Bikes:
Posts: n/a
Mentioned: Post(s)
Tagged: Thread(s)
Quoted: Post(s)
Quote:
Originally Posted by mihlbach View Post
This is nonsense.

I think you can post this in every thread, on every board, on BF.
  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 02:19 AM.