Bicycle Fitting and Sizing

Why Fit

Different Philosophies

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

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.

24" True Angle Tool - Contractor Grade (Heavy-Duty)

18" True Angle Tool

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

http://www.compoundmiter.com/true_angle_tool.html

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

Kits

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.