Bicycle Fitting and Sizing

Serotta

Serotta has been a leader in bicycle fit for quite a while. The established the Serrotta Cycling Institute to further the goals of a better understanding of bike fit.

Fit Bikes

• Calfee Sizer Cycle
• Serotta Fit Bike
• San Giorgio Fig Jig

Goniometers

http://en.wikipedia.org/wiki/Goniometer

A goniometer is used to measure the angle of the knee as well as other joints on the body when doing a fit. The goniometers that are sold throught medical channels are just too short to get good results. You need between 18" and 24". I have found a couple of very good alternatives.

Quint Measuring Systems, Inc. P.O. Box 280, San Ramon, CA 94583 (800)745-5045 http://www.quintmeasuring.com/

• 24" True Angle Tool - Contractor Grade (Heavy-Duty)
• 18" True Angle Tool
• 4" Attachable Dial
• 7" Attachable Dial

I got the 24" version because it is more rugged and thicker.

Kits

• Fit Kit
• Bikefitting.com
• Bike Fit Systems

Local Fitters

• NorCal Cycling in Santa Rosa. $75. They do a pretty good job. Much better than the average bike shop in the bay area. This is where I send most people that need a basic fitting.
• Whole Athelete, San Anselmo, CA, $220-295
• Craig Upton of Performance Lab HC , $150
• PK Racing, in Fairfax. $450-500. Primarily pro road/tri experts. They are very expensive and I have no personal experience with them other than the fact that they are only 3 blocks from my house.
• Cycle Sport, in Oakland. $125

or search Serotta by zip code

Links

• Jack's Bikes - A fit kit walk through
• Cyclemetrics link page
• Pruitt
• Steve Hogg

Some Traditional Numbers

Weight Distribution

Road - 45% Front / 55% Rear

Cleat Position

"5. Make sure that the ball of your foot [centre of the first metatarsal joint] is in front of the pedal axle with the crank arm forward and horizontal. For a rough guide for shoe size metric 36 - 38, 7mm in front; 39 - 41, 8mm in front; 42 - 43, 9mm in front; 44 -45, 10mm in front. It is unlikely that your feet are bigger than that. Don't forget to move the right cleat further back again as outlined in point 3. I know that this is at variance with the commonly given advice but you will find as you try it that it works."

http://www.cyclefitcentre.com/pdf%20final%20docs/SHOE%20AND%20PEDAL%20ARTICLE%208_final.pdf

http://www.cyclingnews.com/fitness/?id=2004/letters07-26#Cleat

http://www.cyclingnews.com/fitness/?id=2004/letters10-11#Ball

Crank Length

18.5% from top of femur to floor.

Inseam:

• < 29 inches - 165 mm crank
• 29 - 32 inches - 170 mm crank
• 32 - 34 inches - 172.5 mm crank
• > 34 inches - 175 mm crank

Frame Size:

• 54 cm or less, 170 mm
• 55 - 58 cm, 172.5 mm
• 59 cm or greater, 175 mm

Knee Angle

30-35 Degrees. More bend conserves more energy, less bend for more power.

31-32 is optimum.

Saddle Height

• Inseam (with cycling shoes) x 0.883 = Top of the saddle to the center of the bottom bracket. (beware oversized feet using this)
• Inseam (with cycling shoes) x 1.09 = Pedal spindle to top of saddle with pedal parallel to seat tube.

• LeMond Method - Adjust the saddle to a distance equal to your PBH* x .883, measured from the top of saddle to the center of the bottom-bracket
• Petersen Method - Adjust the saddle to a distance equal to your PBH x .873, measured from the top of saddle to the center of the bottom-bracket
• Hamley Method - Adjust the saddle to a distance equal to your PBH x 1.09, measured from the top of saddle to the pedaling surface (with the crank at bottom-dead-center inline with the seat tube)
• Holmes Method - Adjust the saddle so your knee is bent 25-35 degrees with the ball of your foot on the pedal (with the crank at bottom-dead-center inline with the seat tube)

Trunk Angle

About 30-40 degrees from level. (45 at most)

Shoulder Angle

90-100 degrees.

Elbow Bend

15 degrees

Stem Length

• When in drops, axle obscured by bars.
• With arms bent 15 degrees in drops, plumb line from nose bisects stem at bars.

Handlebar Height

• 1-2 inches below the saddle for small riders
• up to 4 inches for taller riders.