Go Back  Bike Forums > Bike Forums > Professional Cycling For the Fans
Reload this Page >

Bike Fit Question: Change your crankarms, lower your seat?

Notices
Professional Cycling For the Fans Follow the Tour de France,the Giro de Italia, the Spring Classics, or other professional cycling races? Here's your home...

Bike Fit Question: Change your crankarms, lower your seat?

Old 03-11-10, 05:53 AM
  #1  
Senior Member
Thread Starter
 
xfimpg's Avatar
 
Join Date: Apr 2007
Posts: 3,137

Bikes: RichardZEP

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Bike Fit Question: Change your crankarms, lower your seat?

Hi Everyone

My current bike configuration has 172.5mm cranks.

If I reduce my crank length to 170mm, would that mean lowering the seat by 2.5mm or 5mm?
xfimpg is offline  
Likes For xfimpg:
Old 03-11-10, 06:05 AM
  #2  
Primate
 
Metzinger's Avatar
 
Join Date: Jan 2006
Location: gone
Posts: 2,579

Bikes: Concorde Columbus SL, Rocky Mountain Edge, Sparta stadfiets

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 5 Times in 5 Posts
You should be able to raise the seat.
The measurement saddle-to-pedalstroke-bottom will reduce by 2.5mm.
Seat should be able to come up that amount.
Metzinger is offline  
Likes For Metzinger:
Old 03-11-10, 06:59 AM
  #3  
Senior Member
Thread Starter
 
xfimpg's Avatar
 
Join Date: Apr 2007
Posts: 3,137

Bikes: RichardZEP

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by Metzinger
You should be able to raise the seat.
The measurement saddle-to-pedalstroke-bottom will reduce by 2.5mm.
Seat should be able to come up that amount.
I'm not sure that I follow.
If my crankarms will be shorter, I will therefore be lower to ground - 2.5mm so to speak. If I want to keep the same pedal-to-seat length ration, would I not be lowering my seat?
xfimpg is offline  
Old 03-11-10, 07:41 AM
  #4  
Primate
 
Metzinger's Avatar
 
Join Date: Jan 2006
Location: gone
Posts: 2,579

Bikes: Concorde Columbus SL, Rocky Mountain Edge, Sparta stadfiets

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 5 Times in 5 Posts
When trying to picture a mechanical relationship, it helps to imagine extremes.
Picture:
a: cranks so long they hit the ground. It's hard to reach the pedals because they're on the ground at full extension. Lower your saddle so you can reach those distant pedals.
b: 1cm cranks. It's easy to reach the pedals because they're basically at the level of the bottom bracket. Raise your saddle so you can extend your leg more.
Metzinger is offline  
Old 03-11-10, 07:49 AM
  #5  
Senior Member
Thread Starter
 
xfimpg's Avatar
 
Join Date: Apr 2007
Posts: 3,137

Bikes: RichardZEP

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by Metzinger
When trying to picture a mechanical relationship, it helps to imagine extremes.
Picture:
a: cranks so long they hit the ground. It's hard to reach the pedals because they're on the ground at full extension. Lower your saddle so you can reach those distant pedals.
b: 1cm cranks. It's easy to reach the pedals because they're basically at the level of the bottom bracket. Raise your saddle so you can extend your leg more.
Yes! You're right, because you're measuring from the bottom of the stroke.
I'm so glad there are smarter people out there than me.
Thanks!
xfimpg is offline  
Old 03-11-10, 03:47 PM
  #6  
umd
Banned
 
umd's Avatar
 
Join Date: Sep 2005
Location: Santa Barbara, CA
Posts: 28,387

Bikes: Specialized Tarmac SL2, Specialized Tarmac SL, Giant TCR Composite, Specialized StumpJumper Expert HT

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
You lost?
umd is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
rekon
Road Cycling
17
01-13-15 03:38 AM
Long Tom
Road Cycling
13
03-15-14 05:57 PM
thook
General Cycling Discussion
21
04-13-11 09:21 PM
KasbeKZ
Road Cycling
5
04-19-10 06:45 AM

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.