Bike Fitting & Assessment: Art and Science

 "My goal of every bike fit is to enable my clients a  pain free ride and the ability to ride their best" Dr. Greg Combs

People often ask the below bike fit and bike size questions. This process is mostly a mechanical and static sizing approach.
What size of bike do I need?   
Basically, their inseam is a common reference point.  Most bike size charts note the stand-over height. This is the client's inseam plus another 1-2 inches for comfortable clearance of the top tube. Typically, road bikes require 1-2 inches clearance while mountain or commuter bikes need 2-4 inches.

How do you measure inseam for a bike?
Stand with your back against a wall and spread your feet 6-8" apart. Place a book between your legs and up against the wall, spine up; raise it until snug against your crotch (this mimics your bike seat). Have another person measure from the top of the book (spine) down to the floor.  At May Street Bicycles I we have a specialized devise that measures stand over height.

How do you measure the size of a bike frame?  There are many ways to do this process, but here are some basics.

1. Identify the top of the seat tube, where the seat clamp holds the seat post.
2. Identify the center of the bottom bracket (it's the axle that holds the crank arms together).
3. Measure the distance between the two points (C-T) - this is the length of the seat tube.
4. Record measurements in both centimeters (cm) and inches (to the nearest half-inch).
5. Based on the above metrics the client's bike size can be determined based on the client's height and leg length. Note this is just to get the correct bike frame size.

How do you fit a bike? Now we get to the science of a fit and assessment.
I place the bike on a trainer that is set on a rotating platform to rotate the client to video both sides. Then the client sits on the bike in their riding clothes and shoes (if required, some athletes I assess ride hand cycles).  Then I place tracking dots on the ankle joints, knee joints and hip joints.  Then the client rides their bike while I video them (or use 3D tracking if there are major asymmetries identified).   Then I analyze their riding movement on the bike and assess imbalances and movement differences.  

Below are some pictures of John who is being assessed for a custom handcycle. I analyzed John in different positions to evaluate his hand pedal stroke and power out put in the different positions. While he was at the shop Matt (my assistant coach) had John perform a Functional Threhold Power Test.  This guy is a beast.

This next client purchased a bike at a great deal. But after making adjustments on the bike and then assessing her, the bike was not a very good deal for her.  It did not fit her very well. The top tube was too long and the aero bars and base bar were not very adjustable.

This next client came in after an initial assessment a year ago. He too was on a bike that was too big. But he found a better size bike for this session

Upon completing the above video assessments I begin addressing common causes of faulty movement and provide corrective exercises for my clients, such as:

• Assess range of motion for functional and anatomical abnormalities such as pelvic malalignment.
• Conduct Postural Restoration Institute (PRI) and/or Functional Movement Screening FMS assessments to identify faulty movement patterns and prescribe corrective exercises.
• Perform a comprehensive rider analysis on the bike based on the individual’s range of motion by using state of the art Retul 3-D and Dartfish video analysis technology and saddle pressure analysis technology by gebioMized..
• Demonstrate Muscle Energy Technique (MET) to regain range of motion and alignment of the lower back, pelvis, and extremities. 
• Provide follow up sessions for minor adjustments on the bike.
•  Refer clients with major functional problems to a medical specialist to perform appropriate treatment.

If you are looking to be more comfortable and efficient while riding your bike please contact me for a bike fit assessment.  I offer group packages for clubs and teams.

Yours in Cycling and Fitness,
Greg Combs
President of Fun
​May Street Bicycles is not your typical bike shop. Sure we sell awesome bicycles, provide bicycle repairs, and rental bikes all at great prices. But we do a great deal more such as dynamic bike fitting, metabolic testing, altitude training, and personal training.  ​​