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Key Metrics


What do these mean?
Bicycle Name/Type:

Input suspension geometry

Suspension Length:

Input bicycle geometry and colour scheme

A - Wheelbase: B - Rear axle to fork top:
C - Fork: D - Front axle offset:
E - Wheel radius: F - Wheel inner radius:
G - Headstock length: H - Down tube to fork top:
I - Top tube to fork top: J - Steering stem:
K - Chainstay: L - Bottom bracket to fork top:
M - Seatstay: N - Seat join to fork top:
O - Saddle Displacement: Change drawing line colours
Dimensions in mm. Hover over the input field to see measurement highlighted.

Select a bike model below to load data for that bike:

Map My Bicycle - Steps

To understand the geometry of a bike or to make detailed geometric comparisons between one or more bikes, follow these steps.

Measure your bike (see taking the measurements), enter the numbers into the form above. All dimensions are in mm.

Then, if you want to compare one bike with another, output schematic drawings of your bikes as .png files (with transparent backgrounds), overlay them in graphics packages and visually compare the output dimensions of different bikes or changes to the same bike.

Open each schematic drawing, in a graphics package one on top of the other in a new layer creating a composite schematic like the image on the right, allowing you to make comparisons.

The image shows two bikes compared with each other and was used to decide if a frame was large enough before being built up with components.

Read about the theory behind bicycle frame geometry.


The images that this website produces are 800px wide and 400px high. The scale used is 1000mm to 400px. i.e. to go from mm to px divide by 2.5.

When you hover over the field names in the table you see where you have to take the measurement highlighted in bright orange. As you move the cursor out of the input field the bike schematic will change to represent the new data.

For the 'Compress' / 'Uncompress' buttons to work, "Suspension Length" must be set to a value greater than 0.

The layout of this page is optimised for different window widths. Always run this page in as wide a window as possible. Your current window width is Start px. Also, most browsers provide window content resizing with the keys CTRL and ")" (go back to default), CTRL and "+" (expand content - view less), CTRL and "-" (shrink content - view more). Try these keys out with this page.

Why is this useful?

If you enjoy making changes to improve your bike, for example, fitting different forks and different tyres, mixing and matching different components from different bikes, or you are simply buying a new bike or bike frame but want to know how the frame size and geometry compares to ones you have, then read on... Some examples of the types of problems you may have:
  • You want to buy a new bike but you want one that handles like your old bike, just new components... Amongst all those shiny curves of aluminium or steel which are the critical dimensions?
  • You are going to fit a set of aftermarket forks to your bike but the dimensions are slightly different... What difference will it make to the handling and stability?
  • Before you purchase a different frame, you want to know how its frame size and geometry will compare with one you already enjoy riding.
  • Your bike handles really nervously, or doesn't turn well, why is that?
To really answer these and many other questions you need to understand what the critical dimensions of your bicycles are and what effect they have. Manufacturers sometimes give technical specifications but when you compare bikes these are not always like for like and not necessarily the things you need to know.

With this tool you can:

  • Graphically compare the geometry of different bikes and different components. You measure all of your bicycles, use this tool to analyse the differences and compare this with subjectively how they feel when ridden.
  • Work out what the Trail, Wheel Flop Factor and other dimensions are for your bikes - Trail has a massive effect on handling
  • See the effect of suspension geometry changes. e.g. can I put 120mm suspension forks on my 100mm mountain bike - will the tyre touch the frame - will the trail become negative - will the pedals scrape on the ground!

Design goals

The following design goals were important:
  • In general, it's easier to accurately measure lengths with a ruler than angles with a protractor. To build a diagram of your bike's geometry, this tool could have required that you measure the steering angle which is more difficult than measuring lengths. The measurements that you have to take are not in all cases the measurements that frame manufacturers quote for their frames, (e.g. 'Effective top tube') as this is difficult to measure. It's easy to take the required measurements and important measurements like 'Effective top tube' and 'Bottom bracket drop' are calculated for you.
  • The model allows you to compress the front suspension and reassess the key metrics like Trail.

Save this bike design

Copy the following string. Enter it into a browser to resume analysing this bike geometry.


Output the current dimensions

Create and download a .csv datafile for spreadsheet analysis with all the current data.

Download File

Download image as .png

Hover the mouse over the image to the left of this text (or the main image), right click and choose a suitable browser dependent option.
For example 'Save Image As...'.