Having worked as a bike fitter for over a decade there is one thing that a surprising number of cyclists forget to do: log their fit measurements. While most in-person bike fits will include a record of your bike measurements (if you didn’t get one, ask), for those that haven’t had an in-person fit, or didn’t get any measurements, it isn’t always obvious that taking measurements is something you should do.
In this post we’ll cover the why, what and how of logging your bike fit measurements.
Why you need to measure your bike
It’s always important to have a record of your position on the bike for the simple reason that you might need to replicate it. Bikes break, parts slip, get moved, get stolen, or more optimistically maybe you get to travel and have to rent a bike (or set your own back up after boxing it up). If you don’t have a record of your position it’s going to be much harder to recreate your position.
Picture this: you have spent the last few months refining your position by making small tweaks to your seat height and stem position. You’ve got your bike feeling perfect - like an extension of your body. You are on a glorious ride and you stop for a coffee, it’s a safe neighborhood so you don’t lock your bike. You come out and it’s gone! Luckily you have great insurance so you get a replacement bike right away. After weeks of riding the new bike you still can’t get it to feel quite right, even though it’s the exact same make/model. If only you had a set of detailed measurements you’d be able to get back to that perfect position you had worked so hard to find.
Bike fitters and shop employees see all sorts of scenarios like this regularly. Don’t wait until it’s too late - go take those measurements right now.
The Four Measurements You Need:
The four key measurements you need to reliably record your position can be split into two broader positions:
- Saddle Position
- Grip Position*
Both have two components (which is how we get to four), vertical and horizontal, and will be referred to in this article as:
- Saddle Height
- Saddle Setback
- Grip Drop
- Grip Reach
Let’s dig into why each measurement is important, and how to take it.
*In this article we’ll focus specifically on Road/Mountain/Hybrid bikes. We’ll have another post for Time Trial and Triathlon bikes as they are measured slightly differently.
A Tip For Measuring
Before we get into the how, the most important thing to do when taking your measurements is to be consistent in your method. There are a number of different methods you can use to take each measurement, and even what reference points you choose is ultimately up to you. What you need to remember is that your measurements are only as useful as they are repeatable so make sure you know what points you are measuring and stick with it.
Your saddle position is comprised of two main measurements
- Saddle Setback
- Saddle Height
Generally these two measurements reflect the horizontal and vertical(ish) distance from the saddle to the bottom bracket to the saddle. Why the bottom bracket? Because the bottom bracket is the one place on any bike that we cannot change. Regardless of any changes in geometry between bikes, our feet always move around the bottom bracket which makes it the perfect reference point to base our position around.
Saddle Height and Setback measurements always start at the center of the bottom bracket (BB). If you remember elementary school geometry, we’ll consider the BB as the origin on a graph. Why the BB and not the pedal at the bottom of the pedal stroke? Using the pedal opens up a number of measurement variables, that while potentially relevant, these variables can be overcome in other ways - remember the key here is repeatability.
How to Measure
For all the measurements you’ll want to make sure your bike is on level ground and placed so it is standing vertically (not leaning to one side or another).
Saddle Reference Point
Measuring both saddle height and setback requires picking a point on the saddle to use the reference point. Where you measure on the saddle will influence what measurement you get. Though there are several methods for selecting a reference point*, we recommend using the center of the length of the saddle as your reference point. This will help normalize for any difference in saddle lengths. Going forward we’ll call the saddle reference point SRP.
To find the SRP measure the length of the saddle and divide by 2 - then measure from the tip of the saddle to this point and mark it. You can either put a piece of masking tape and mark that with a pen or mark directly on the saddle with a colored permanent ink marker.
*It is worth noting that the UCI and some fit software use the tip of the saddle as the reference point. So if you are measuring your bike for a UCI sanctioned event or comparing to a fit report from a bike fitter it may be worth also using the tip of the saddle.
Horizontal distance from center of bottom bracket to saddle reference point. There are a number of ways to take this measurement. Our preferred method to take this measurement is to place your bike with the back wheel against a wall (finding a corner is helpful as the adjacent wall can help keep the bike upright). Measure the horizontal distance from the wall to the center of your bottom bracket, and the wall to your SRP. Then use the following simple calculation:
Saddle Setback = (wall to bb) - (wall to SRP).
Direct distance from center of bottom bracket to saddle reference point. This is measured inline to the reference point so your tape measure will be on an angle from the BB to the reference point not perpendicular to the ground or directly following the seat tube (but in some cases they may line up).
Grip drop and reach refers to the vertical and horizontal distance from a point on the saddle to the place where you interact with the steering of the bike, your grips. On most bikes this will be where your hands naturally hold the handlebars.
As mentioned early, whereas saddle position is measured with the bottom bracket as the reference, grip/arm pad position is measured from the saddle reference point. In practice this means both measurements are tied back to the bottom bracket, and will help you replicate your position on any bike.
Grip Reference Point
Similar to measuring the saddle position, measuring grip position requires picking a point on the handlebars to measure from. There are many different types of handlebars out there, and multiple hand positions to choose from. These are the reference points we recommend for the most common handlebar options. We will call this point the GRP.
Drop handlebars (e.g. road, grave, cx, touring, etc): measure to the point on the
hoods where the crook of your hand meets the hood.
Flat handlebars (e.g. mountain bikes, hybrids, etc): measure to the point of the grip where the crook of your hand meets the grip.
Grip drop is the vertical distance from saddle reference point to GRP
The easiest way to take this measurement is to place your bike upright against a wall. Measure the vertical distance from the floor to the grip reference point, and the floor to your SRP. Then use the following simple calculation:
Grip Drop = (Floor to SRP) - (Floor to GRP)
A negative number indicates the saddle is higher than the grip.
Grip reach is the distance between the SRP and the grip reference point. This is measured exactly as pictured, a straight line between the two points.
It’s important to keep in mind that grip reach on its own is a factor of numerous factors, the saddle to bar drop, overall reach, bar width, bar reach, stem length. We have a blog post here on adjusting reach.
Equipment differences can play an important role in the overall fit and feel of your bike, so be sure to also log details about other components and equipment including:
- Crank length
- Handlebar width and model (most handlebars have different shapes),
- Saddle make/model/width,
- Pedal model
- Shoe model
While individually it may seem as though changes to these items may be insignificant, they can be the cause of fit issues and keeping track can be a great help to tracking down the source of problems.
While it is somewhat rare that you’ll need to dig so deep into your position that nuances like these will be needed but it’s always better to have them and not need them than to not have them and need them.
Normalizing for differences - Often you can normalize for differences between parts or bikes if you are, say, renting or borrowing a bike, or replacing an old bike with one with a different geometry. For example, if you borrowed a bike with a different crank length, you’ll need to normalize for the difference. If the cranks are longer than yours, then you’ll need to lower your saddle by the difference, if they are shorter then you’ll need to raise your saddle. For more on matching bikes your fit to a different bike or components check out our blog post here.
Last but not least, store your bike measurements and check them regularly.
Save your measurements! It doesn’t matter how good your measurements are, if you don’t have a copy of them when you need them they won’t help much. We recommend storing your measurements online (like in our bike measurements form) or emailing yourself a copy so you always have them when needed.
Now that you have those measurements, check your bike regularly to make sure your position hasn’t changed. It isn’t uncommon to have people show up for a bike fit because they are in pain and it comes down to their seatpost or handlebar slipping.