How To: Use Your Bike Fit Measurements

If you are looking to replicate your position on a second bike or an indoor bike this winter, this is how to do it!

The information here can also be used to check your position on your current bike or take a new set of measurements altogether.

This article is most useful for riders who already have a set of measurements from their Foundation bike fit. However if you have measurements from another fitter, then you should still be able to apply the principles and set up your recorded position. Just be aware that different fitters will measure to different landmarks and may provide information in a different format. These are all relevant ways of providing measurements but we do things the way we do because we feel it’s the most accurate and also the easiest to understand.

Finally the measurements shown in this article are most relevant for setting up a road bike / drop handlebar position. There will be further articles to cover the specifics of mountain bike and time trial / triathlon bike setup but the core methodology and principles still apply.

Things You Will Need

  • A tape measure
  • Tools to adjust your bike e.g. allen keys, torque keys
  • A laser level – if you want to go pro!
  • An angle finder / angle app on your phone
  • Your bike fit measurements
tools for measuring your bike

If you’ve had a fit from us, you will have a CAD drawing of you bike which looks like the image below. It’s easy to be intimidated by all the numbers but the following steps break all the measurements down into easy to understand sections. 

CAD Bike fit measurements from foundation bike fit

The Primary Measurements

Your primary measurements describe the position of your saddle, hands and feet, relative to each other. These are presented as coordinates, where the zero point is the centre of the bottom bracket. These are what you want to be able to measure and replicate across different bikes.

Primary bike fit measurements, no bike
Primary bike fit measurements

The Secondary Measurements

These will be contained within the dialogue box at the bottom of your measurements diagram. Although important these can be measured more easily and independently of the primary measurements. Often these dimensions are fixed and can only be changed if the component itself is swapped out e.g. crank length, handlebar width etc.

Secondary bike fit measurements

Before you start

  • Give yourself enough time – There’s nothing worse than having to rush through a job. Set aside a good amount of time to do this so you can give it your full attention and your body will thank you out on the ride! 
  • Familiarise yourself with your bike – Gone are the days when all seatpost clamps were located next to the seatpost! Every bike is different so understand where the nuts and bolts are located on your bike and what tools you need to make the adjustments. E.g. Some Canyon seatpost adjustment bolts are located low down, on the back of the seat tube. BMCs have a hidden allen key bolt underneath the top tube where it meets the seat tube. Some Basso bikes require three torque keys to be loosened on the back of the seat tube. If you’re unsure how to adjust your bike, pop to your local bike shop for some advice. If you don’t know how to adjust things like stems, brake hoods and handlebars check out the links for instructional videos from GCN. 
  • Have the same contact points if possible – If you are trying to set up a second bike to your measurements, ideally you want your second bike to have exactly the same contact points as the bike you are trying to replicate i.e. the saddle, handlebars, shifter hoods and shoes / pedals. This makes it much easier to measure and the feel of the position will also be the same. If you have a different saddle or bars, have a go at setting up the second bike, take it for a spin and see if it feels comfortable. The measuring methods outlined will still work if you have different components but you may have to make a few further tweaks after riding to get it feeling spot on. 
  • Ensure your bike is on a level surface – Mounting your bike on a turbo trainer is usually the easiest way. You may need to raise the front wheel (use a riser block or a stack of magazines) so the bike is level i.e. the height from the floor to the centre of the wheel axles should be the same. Some trainers, like Wahoo, don’t require a riser block for the front wheel.
Level your bike
Make sure your bike is level
Wahoo Kickr no riser block required
Some trainers do not require a front wheel riser block

Measuring the Primary Measurements

1. Set the Saddle BRP (Biomechanical Reference Point)

This is the centre point of the saddle where the saddle is 80mm wide. Mark this point and use this as a landmark from which to measure your seat height. Saddle stack (Y) and Saddle reach (X) also use the BRP as the measurement point.

BRP 80mm measurement point CAD
BRP meaurement point

Why do we use the BRP? Every saddle has a different profile, width and shape. So the BRP provides a landmark which can be easily replicated on any saddle and so provides consistent measurements even across different shaped saddles. It’s not an absolutely perfect method but will get you very close e.g. if you have a very different shaped saddle like an ISM. It is also widely used by many bike fitters, though some may set the mark where the saddle is 70mm wide or another point of their choosing.


2. Measure Saddle Stack & Reach

Saddle stack and reach bike fit measurement CAD

There are several ways to do this. 

a) Laser Level: The most accurate and easy way to measure is to use a crosshair laser level. This is the method we use on a daily basis at the studio. Make sure the laser level is directly perpendicular to your bike. Centre the crosshairs on the centre of the bottom bracket and then you can easily use a ruler or tape measure to measure the horizontal and vertical distances. Laser levels can be as cheap as £15, so this is a very accessible way to get good measurements (also great for hanging all your pictures up straight!). Don’t forget you’ll need a tripod to mount your laser on too.

Bike fit laser level for measurements
Centre the laser on the bottom bracket
Laser saddle setback ruler measurement
Measure saddle setback using a laser

b) Wall Method: The diagram below shows the initial measurements you need to take. Then using a few simple calculations you can work out your Saddle Stack & Reach. This works best for actual bikes. You may need to get a little more creative for measuring an indoor bike e.g. Watt bikes, since they can be more difficult to move and place against a wall. 

Wall method saddle stack and reach measurements
The wall method: back your bike into the corner of a room
  1. Start with your bike on a hard, level floor and set the bike into a corner. Place the rear wheel against a wall and make sure the bike is as perpendicular to the wall as possible. 
  1. Measure and record the Bottom Bracket X & Y dimensions – ideally using a straight edge like a carpenter’s level is most accurate. Tape measures will bend as they get longer.
  1. Measure the Saddle X & Y dimensions.
  1. Now time for some maths! 
  • Saddle Stack (Y) = Saddle Y – Bottom Bracket Y
Wall method saddle stack
  • Saddle Reach (X) = Bottom Bracket X – Saddle X
  • Saddle setback = Saddle Reach (X) – distance from tip of saddle to BRP (use this as a check against your measurements)
Wall method saddle reach

3. Measure Saddle Height

a) Always measure from the left side (non-drive side) of the bike as the drivetrain won’t get in your way.  

b) Use a straight edge to measure the distance from the middle of the bottom bracket to the top of the saddle. Measure to the 80mm BRP landmark. 

TOP TIP: Use this direct saddle height measurement as a check after you have set up Saddle Stack Y & Reach X. Why? If you set your saddle height first, then move the saddle back / forward to set your saddle setback – your seat height will have changed! Bringing the saddle forward, effectively reduces your saddle height and visa versa. If you can, always start by setting up Saddle Stack Y & Reach X first.

Finally direct saddle height is still a useful measurement to keep in the back of your mind. For example, if you are travelling with your bike and need to check the saddle height on reassembly this is still the quickest measurement you can do to

Saddle height measurement
Measure from the top of the saddle (at the BRP) to the centre of the bottom bracket

4. Measure Cockpit Stack and Reach

By now the measuring principles and process should be pretty clear. Turning our attention to the cockpit of the bike, the critical measurements here describe are where your hands are placed. i.e. Hood Stack & Reach. If you’re using the laser level, use the image below for guidance. For the wall method scroll down.

cockpit stack and reach bike fit measurements

When selecting the point of measurement on the brake hoods itself, we usually measure from the centre of the ‘well’ of the hood, as it starts curving upward. This is usually the point where the hood rests against the area of your hand which is in between your thumb and forefinger.

Hood grip stack and reach marker point

Wall method:

  • Hood Reach (X) = Hood X – Bottom Bracket X
  • Hood Stack (Y) = Hood Y – Bottom Bracket Y
Wall method

When measuring handlebar Stack & Reach, bear in mind that different handlebars will have different shapes and dimensions which will affect your Hood position. So if you are replicating a position across different bikes be aware of the different handlebar dimensions.

handlebar reach and drop variations

Measuring The Secondary Measurements

1. Crank Length

This is usually printed on the back of the crank arm itself. If you need to measure, it is the distance between the middle of the bottom bracket axle to the middle of the pedal spindle.

crank length marker
Crank length is usually written on the back of each crank arm
Crank length measurement

2. Saddle Angle

You will find much variation in how people measure saddle angle. The difficulty arises because saddles come in all shapes and sizes. The method we use is easy to replicate and provides consistency. All you have to do is place a flat surface on top of the saddle, then measure the angle of that surface using either a angle finder tool or a phone app.

Saddle angle with box
Saddle angle with app

3. Handlebar Width, Reach & Drop

The diagram below is pretty self explanatory and we touched on how handlebar reach can affect your overall hand position in the section above. Just be aware that most manufacturers will measure road handlebar width from the centre point of each side of the bar (know as centre-centre). Some companies like Deda provide their widths measured from the outside edge of the bar to the other outside edge (known as outside-outside). So a 420mm width Deda bar measured outside-outside is the same as a 400mm width measured centre-centre.

Handlebar dimensions
Handlebar centre-centre outside-outside
Understand how different manufacturers provide different dimensions for the same size bar

Conclusion

This article should give you a comprehensive overview on how to use your bike fit measurements and understand the principles behind the measurement methods too. The hope is that this article will become a resource which you can re-use time and time again. Got a new bike? Dig out your tape measure and this article! We’ve left out some of the simple measures like stem length and spacers height to concentrate on the more involved measurements, but if you would like us to add any more info or have any questions at all, please do send us an email. We’ll keep updating this article and will be adding some more around TT and mountain bike measurements.

Happy riding!

Riders cornering a sunny descent on a smooth road

One thought on “How To: Use Your Bike Fit Measurements

Comments are closed.