Indoor Bike Improvement #7 - Better Bike Fit

7 OF 10 - BETTER BIKE FIT

Indoors and out, my bike position changes a small amount each season.  

My road bike tends to define my optimal position at the end of the summer. It includes millimeter adjustments made over the course of several thousand kms.  Similarly, my indoor bike defines my optimal position at the end of the winter.

When I have settled on a new optimaI position, I like to transfer it to my other bikes, including: road, gravel, indoor and time-trial.  

Transferring Bike Measurements

Assuming you have one bike with your optimal position, you need a method for transferring the riding position to multiple bikes.  

Prerequisites and Notes:

Cranks - All bikes have same crank length. Watch for small differences in pedal platform height.

Saddles vary - They can have different lengths and widths. To create a standard measurement position on all saddles, I use the top of the saddle where it touches the pelvic bone. This is near but not exactly the widest point on most saddles. I put a mark on the saddle since this point is used in subsequent measurements. 

Handlebars vary - Brake levers will often need to be moved to accommodate different reach and drop radius angles between handlebars.  Keep this mind. A solution is provided below. 

Here's the method I have used for decades.

1. Seat Height: Measure distance from the centre of the crank axle to top of the saddle at the pelvic bone position.

2. Saddle Setback: Use a vertical level or plumb-bob to measure the horizontal distance from the centre of the crank axle to the pelvic bone position.

3. Handlebar Reach: Measure the distance from the pelvic bone position to the back edge of handlebar tops. 

4. Handlebar Drop: Use a horizontal level to measure the vertical distance from top of saddle (at the pelvic bone position) to the top of the handlebars.

5 - 8. On the target bike: Adjust the target bike to reproduce each of the 4 measurements from the reference bike.  Be prepared to iterate when you discover you didn't measure everything correctly. 

A Better Way

Setting up a new bike requires 8 steps. It can be tedious and error prone. To make bike fit transfers easier, I constructed The Fit Frame. It allows critical measurements to be transferred in one step.  

The Fit Frame has adjustable arms that lock the Seat Height, Saddle Setback, Handlebar Reach and Handlebar Drop measurements. 

Reproducing bike fit is as simple as moving The Fit Frame to another bike.  

Movable bumpers mark the crank axle centre, pelvic bone position, handlebar height and reach along with other critical heights and distances. A pair of spirit levels keep the frame properly aligned on all axes.

This version also has extension arms to measure brake hood position on tricky bikes like my SB20 indoor bike.

Made with from a 3D Printer

The Fit Frame is not quite 3D printed. It's made from the aluminum extrusions, gusset plates and hex fasteners used to construct 3D printers 😂.

Parts List

• Aluminum extrusions
• Connector and related hardware
• Spirit levels

Plus a table saw to cut everything along with a some patience to figure out how to assemble this kind of frame.

=========== UPDATE 🎉 ===========

Today, I received a new saddle from AliExpress. It is flatter, thinner (with wider nose) and longer than the Stages saddle. I was able to mount and replicate my position versus the original saddle in a few minutes using the The Fit Frame. Adjustments included more setback and slightly lower seat height. My back and knees said thanks.

Saddle Details: There are two models.

1.  Nylon frame and steel rails  260g  I bought this one for indoor riding.
2.  Carbon frame and rails  160g  (recommended) 25% higher cost. Appears to be more robust. I bought this one for outdoors.