How to Measure Your Position Accurately and Repeatably

HOW TO MEASURE YOUR POSITION ACCURATELY AND REPEATABLY

Tools: You will need:

2 x 300ml steel rules
A long carpenters’ level
A measuring tape
A marker pen with reasonably fine tip
A dial protractor (angle finder) or digital level
Indoor trainer

Level the bike: Mount your bike in an indoor trainer and use a long carpenters level held between the centre of the front and rear axles to ensure that the bike is dead level. You will need to use a phone book or some other item to lift the front axle high enough to be level with the rear axle. A phone book is ideal because you can open it and place the front wheel under the correct number of pages until you achieve a level position. If you don’t level the bike properly, every measurement you take will be inaccurate, so it is critical that this first step is done properly.

You can note down all the measurements listed below at the end of this form.

Seat height:

Measure the length of the flat section of your seat rail and place a marker pen dot at the half way point.

Lay a 300mm steel rule along the top of your seat. Use a tape measure to measure from centre of bottom bracket to the underside of the steel rule ensuring that the measuring edge of the tape passes through the dot you have placed on the seat rail. If you have a perineal cut out or groove down the centre line of the seat, place the steel rule on one edge of the rear of the seat so that it contacts the high point at the rear of seat

Crank length: I will need to know this and whether you are using a single, double or triple chain ring and what size the chain rings are. Crank length can usually be found inscribed some where on the inside edge of the crank arm. For road I need to know whether it is a double chain ring, double chain ring compact or road triple crank set.

Seat angle relative to horizontal: Place a dial protractor or digital level (available at any hardware store) on top of your seat and read off the angle. + equals nose up; - equals nose down. If your seat has a groove or perineal cut out through the middle of it, ensure that the steel rule is laid along the edge of the seat so you are measuring from the high point at the rear of the seat to the high point at the front of the seat.

Seat depth: Leaving the rule laid along the top of the seat, use the other rule to measure the vertical distance from the centre of the diameter of the seat rail to the under side of the rule laid along the seat. The rule that you are holding vertically should pass through the mark you previously placed at the midpoint of the flat section of the seat rail.

Seat nose to centre of rail: Ensure that the rule laid along the seat is now moved to the centre line of the seat even if there is a groove or perineal cut out. Hold a rule vertically against the nose of the seat to ensure that the other rule laid along the seat does not protrude further forward than the exact nose of the seat. Now move the vertical rule to the centre of the seat rail length (previously marked) and read off where it intersects the rule laid horizontally along the top of the seat. You are looking for the distance from a point directly above the marked centre of the seat rail to the nose of the seat

Seat setback: Hold the long carpenters’ level vertically with the edge passing through the centre of the bottom bracket. While ensuring that the bubble of the level is centred, hold a steel rule against the edge of the level and measure the distance to the nose of the seat.

Seat nose to handlebar distance: Ensure that the front wheel is pointing straight ahead. Measure from the nose of the seat to the centre of the top of the handlebar adjacent to the edge of the handlebar stem’s bar clamp. The reason you are not measuring to the centre of the stems bar clamp is because the CAD drawing on Page 5 uses the hypothetical centre of the handlebar (inside the handlebar) as an input. The parallax involved in measuring as I have described; to the centre of the bar adjacent to the edge of the bar clamp of the stem will yield the same hypothetical measurement + / - 1mm

Seat to handlebar drop: Hold the level horizontally so that one end of the level is on the seat directly above the dot on the seat rail. Use a steel rule to measure from the bottom edge of the level to the top of the handlebar adjacent to the stem bar clamp. For an mtb or 26.0 mm standard diameter road bar, add 13mm to the observed measurement. For an oversized 31.8mm mtb or road bar, add 16mm to the observed measurement. Again, my CAD program uses the hypothetical centre of the bar as an input, so adding the radius of the bar gives an accurate measurement.

Bar angle (road or bullhorn bars): Remove your bar tape and hold the dial protractor against the underside of the rearmost section of your bar drops. A + angle means that this part of the bar runs up towards the front. A – angle means that it runs down towards the front.

Brake lever height: With bar tape removed, hold a steel rule against the underside of the rear most section of your drop or bullhorn bar. Use a second steel rule to measure from the first steel rule to the bottom of the brake lever. You will have always have a gap or an overlap. A gap is a + measurement (bottom of brake lever is higher than bottom of handle bar) and an overlap (bottom of brake lever is below bottom of handlebar) is a – measurement.

RECORD INFO BELOW

BIKE TYPE: (highlight one) Track drop bar Track pursuit bar Road Tri

Flat bar road Road touring Mtb 26”

Mtb 29” Other (specify)

CRANK LENGTH: MM

CRANK TYPE: (highlight one) track/ fixie single chain ring road double

road compact double road triple

mtb triple

SHOE SIZE, BRAND AND MODEL

SEAT BRAND / MODEL:

SEAT HEIGHT: MM

SEAT ANGLE RELATIVE TO HORIZONTAL: + / - (highlight one) degrees

SEAT DEPTH: MM

SEAT NOSE TO CENTRE OF RAIL: MM

SEAT SETBACK: MM

SEAT NOSE TO HANDLE BAR DISTANCE: MM

SEAT TO HANDLE BAR DROP: MM

HANDLE BAR BRAND:

HANDLE BAR MODEL:

HANDLE BAR TYPE:

HANDLE BAR WIDTH (specify whether you are measuring bar width centre to centre or outside edge to outside edge)

WHEEL SIZE (highlight one) 700c 650 c Mtb 26” Mtb 29”

TYRE DIAMETER: (marked on side of tyre. Road bikes will have this in mm. Mtb’s will have this in inches)

BRAKE LEVER HEIGHT: MM

BRAKE LEVER BRAND / MODEL / NO. OF SPEEDS (example = Shimano Ultegra 10 speed)

RIDER WEIGHT LBS / KG (nominate one)

RIDER INSEAM LENGTH MM