Bicycle Fitting and Sizing

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Why Fit

Different Philosophies


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

My fit bike

I got myself one of the Calfee/Mikkelson Sizer Cycles. Fun!!! I also have a PowerTAP rear wheel for it to measure power gains in different postitions.








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

  • 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.


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
  • AriaVelo, in Santa Rosa.
  • HyperCat Racing, SF

or search Serotta by zip code


A cool poster from Ritchey Logic:

Some Traditional Numbers

Weight Distribution

  • In drops decending: 45% Front / 55% Rear
  • On tops climbing: 40% Front / 60% Rear
  • On hoods, out of saddle, sprinting: 50% Front / 50% Rear


For trail I prefer a setup that sets the rider as far back as possible while maintaining control on steepest climb without too much fussing.

Fox racing shox recomends 55% for X-Country, 65% for Freeride, and 70% for Downhill.

When designing a frame from scratch, wheel offset from BB along wheelbase can be used as a ballpark start.

  • Road - 58.5%F/41.5%R
  • Trailbike - 61%F/39%R
  • MTB Race 60%F/40%R.

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."

Crank Length

39.5% of femur length.

L(mm) = 2.16% x I(mm)
"As a matter of fact, a large, persistent drop in cadence is usually a good indication that the crank is, in fact, too long."
2.10% for taller riders

Popular Guides Height Inseam Cranklength

under than 5' <=70 cm. 165
5' to 5'2" <=74 cm. 167.5
5'2" to 5'7" <=80 cm. 170
5'7" to 6' <=86 cm. 172.5
6' to 6'5" <=93 cm. 175
taller than 6'5" <=99 cm. 177.5 - 180.0

Traditional Recomendations Height Inseam Cranklength

under 5'7" 74 to 80 cm. 170
5'7" to 6' 81 to 86 cm. 172.5
Over 6' longer than 87 cm 175

18.5% from top of femur to floor.


  • < 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
  • Gonzalez and Hull, Bivariate optimization of pedaling rate and crank arm length. Journal of biomechanics 1988, vol. 21, no10, pp. 839-849
  • Danny Too; Gerald E. Landwer, The effect of pedal crank arm length on joint angle and power production in upright cycle ergometry. Journal of Sports Sciences, Volume 18, Issue 3 March 2000 , pages 153 - 161

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

  • Shoulder angle 90 degrees +/- 5 degrees.
  • 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.