MTB Positioning Chart
This article will describe the use of the MTB Positioning Chart for competitive road bicycles. A similar article for road bikes is at Road Bike Positioning. The chart is intended for use primarily by the mechanic, although it can be used by the cyclist. It is often useful to quantify and record the various aspects of a cyclist positioning adjustments. It can also be useful for a cyclist to track and record changes to his/her position. For example, if saddle height is raised, the new height and date of change can be noted. This will allow the cyclist to track changes in performance. Additionally, if the bicycle is lost or somehow ruined, and a new bike must be quickly built, this chart will help in setting up the new bike to closely match the original positioning.
The MTB Positioning Chart can be downloaded as an Adobe® PDF file. The charts contain auto-fields and data may be typed directly to the chart once it is downloaded. See Adobe® if you do not have the Adobe Reader program.
Tools to aid in completion of this chart are a metric tape measure, angle protractor, plumb bob, and straight edge. Begin with the bicycle on level ground. If possible mount bike on trainer and level bike by checking that both wheel axles are the same distance from the ground.
There is often more than one method for measuring a component or position. It is important that the user be consistent and that the method of measuring is noted. Record all units of measurement. For example, record "50cm" for fifty centimeters, and "50mm" for fifty millimeters. Record and note with the assumption that someone else will need to set up a bike from only this chart.
Begin by recording customer/rider information, such as name, address, etc. Also record bike make, model, year of production, and serial number. Also record bike's color scheme and any unique or obvious physical characteristics that might distinguish this bike. Assume this will be used in a police report of a stolen bike. It is also recommended that the traveling rider carry a recent photo of the bicycle.
A: Saddle Height
Record saddle height and note method of measurement. A simple method is to place a straight edge on top of the saddle and record height from either bottom bracket center or the pedal spindle center to the lower edge of straight edge. Measure along the seat tube.
B: Saddle Height Over Bars
Record bar-to-saddle height difference. A simple method is to measure perpendicularly from saddle to ground, and then bar to ground, and take the difference between these two measurements. Measure from top edge of grip, and from straight edge on top of saddle.
C: Saddle to Handlebar Reach
Measure from saddle tip to the center of the bars at the stem. This gives a reference for bar reach.
D: Saddle Angle or Tilt
Using a straight edge on top of saddle, measure saddle angle from horizontal. Circle either "upward" or "downward" sloping angle on chart as appropriate.
E: Saddle fore-aft
Drop a plum bob line from the saddle tip and measure distance from line to center of bottom bracket. It is easiest to tape line to saddle so it hangs from saddle end and extends freely toward the ground.
F: Saddle Brand and model
Record saddle brand and model.
G: Stem Length
Measure center of the stem binder bolt to the center of the bars. On a front-plate type stem, this is usually to the gap at the plate.
H: Stem Angle
Record the stem angle from horizontal. Especially on shorter stems, hold level finder so it is parallel to stem angle.
NOTE: Some stem manufacturers specify stem angle using the steering column as a reference. If this angle is known, record this as well. It is possible to measure the manufacturers angle by taking the stem angle and the quill (steering column) angle. Stem angles sloping upward are recorded as positive numbers, while stem angles sloping downward should be recorded as negative numbers. For example, a bike is measured and the angle from vertical is 18-degrees. (This means the headtube angle as the bike sits is 72-degrees.) The angle from horizontal is 25-degrees. The manufacturer's angle is then 90 - 18 + 25 = 97 degrees. In the right image below, assume the stem sloped downward 6 degrees instead. The manufacturer's angle is then 90 - 18 + (-6), or 66 degrees.
Manufacturer's angle = 90 - Angle from Vertical + Angle from Horizontal
I: Handlebar brand and model
Some riders prefer a particular brand and shape of bar.
J: Handlebar Width
Measure bars from end to end.
K: Handlebar Tilt
Flat bars are typically made with a slight bend. This can be difficult to measure, especially with grips on the bike. In the example images below, the left image may be recorded as "slightly up". The center image would be "level" and the right image would be "slightly down".
L: Handlebar Extensions
Measure angle of bar ends from horizontal.
M: Brake Level Angle
Measure angle of brake levers from horizontal. The lever body of various manufacturers may not allow direct measurement of lever action. Hold protractor parallel to movement of lever.
N: Brake Lever Reach
If brake levers are not set at full extension, record lever distance from bars. Record from grip to inside edge of lever at closest point.
O: Crank Length
Record crank length. Cranks are measured from the center of the pedal mount to the center of the spindle square. Arm length in millimeters is typically labeled on the back of arm.
Record the pedal make and model. Changing pedal types may affect the saddle height.
Record shoe size, make, and model. It is also useful to record user preference of either a fixed or floating type of cleat. The cleat position on the sole may also be recorded.
Rotation: Engage shoes on pedals, without rider. Hold shoe parallel to crank. Measure distance from crank bolt to center of shoe sole. If the pedal has adjustable float, hold sole in middle of float range. If cleat has float, hold sole toward crank.
Fore-Aft: Record cleat fore-aft position on sole by measuring from tip of sole to cleat.