Go Back  Bike Forums > Bike Forums > Fitting Your Bike
Reload this Page >

Need some help with geometry chart

Fitting Your Bike Are you confused about how you should fit a bike to your particular body dimensions? Have you been reading, found the terms Merxx or French Fit, and don’t know what you need? Every style of riding is different- in how you fit the bike to you, and the sizing of the bike itself. It’s more than just measuring your height, reach and inseam. With the help of Bike Fitting, you’ll be able to find the right fit for your frame size, style of riding, and your particular dimensions. Here ya’ go…..the location for everything fit related.

Need some help with geometry chart

Old 04-23-19, 03:56 PM
Senior Member
Thread Starter
Join Date: Jan 2014
Posts: 76
Likes: 0
Liked 0 Times in 0 Posts
Need some help with geometry chart


I was wondering if you could help me with interpreting a geomety chart.

I currently have the size S of the first and was wondering if it would be possible to setup the M/L of the second to a similar reach.

I have the first setup with a 76.5 saddle height with 6.5cm of setback with a reach of 52. Many thanks for any help. I'm confused in part as the effective top tube length is so different yet the reach appears similar.

Last edited by Ali89; 04-24-19 at 01:51 AM.
Ali89 is offline  
Old 04-24-19, 12:44 AM
Senior Member
AnthonyG's Avatar
Join Date: May 2005
Location: Queanbeyan, Australia.
Posts: 4,135
Liked 420 Times in 289 Posts
The short answer is that yes, you can setup the medium frame to be very similar to the small frame.
The reach and stack are the important figures that are hard to fudge.

In truth 700c wheeled bikes can only be made down to a 53/54cm size. Smaller than that they just fudge the geometry to make it look right on a spec sheet.
The difference that's confusing you is that the small frame has a steeper seat tube angle that's pushing the saddle forwards towards the handlebars giving a shorter top tube length on paper. If you go to the trouble of maintaining the same saddle setback then they are pretty much identical with the small having a lower stack/head tube length.

The medium frame will have higher handlebar height without adjustment and a good feature is that the medium frame will allow you to experiment with moving the saddle back giving you more saddle setback than present.

EDIT, OK, I was slightly confused and was only comparing the small to the medium of the same design but the principles still hold. The small and mediums are VERY close. In truth you can't build a good small with 700c wheels and they are just a medium that is fudged on way or another to make it look/seem smaller.

Last edited by AnthonyG; 04-24-19 at 07:08 PM.
AnthonyG is offline  
Old 04-24-19, 09:10 PM
Senior Member
obrentharris's Avatar
Join Date: May 2012
Location: Point Reyes Station, California
Posts: 4,567

Bikes: Indeed!

Liked 3,549 Times in 1,158 Posts
The shallower seat tube angle of bike 2 (M/L) increases the effective top tube length of that bike.
If you are currently running a setback seatpost with bike 1 (S) you may want to use a straight post with bike 2 since the shallower seat angle will place you farther forward in relationship to the bottom bracket/pedals.
Note that the stack on bike 2 is 14.4mm higher than bike 1 so your bars will be considerably higher unless you are currently using a stack of shims under your stem.
obrentharris is offline  
Old 04-26-19, 10:24 AM
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Liked 1,360 Times in 866 Posts
Big sheet of paper and draw it out full size?
fietsbob is offline  
Related Topics
Thread Starter
Last Post
Fitting Your Bike
11-16-16 05:35 PM
Fitting Your Bike
02-02-16 02:42 PM
Fitting Your Bike
05-12-15 06:18 AM
Road Cycling
04-26-14 09:23 AM
Road Cycling
12-07-12 03:49 PM

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 - Your Privacy Choices -

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