Geometry charts, demystified

Geometry charts are full of helpful info when it comes to figuring out if a bike will be a good fit for you. This article brakes down what each measurement found on an Xtracycle geometry chart means.


1. Head tube length

xtracycle geometry

The head tube is the front most part of the bike frame where the front fork installs through. The HEAD TUBE LENGTH is measured from the top of the head tube to the bottom of the head tube.


2. Fork length

xtracycle geometry

The fork is the front part of the bike that holds the front wheel. The FORK LENGTH is measured from the bottom of the top tube to the axle.


3. Fork rake

xtracycle geometry

Imagining that there is a line going straight down from the head tube, the FORK RAKE is the distance the actual fork is from this imaginary line.


4. Seat tube length

xtracycle geometry

The seat tube is the part of the bike that the seat post installs into. The bottom bracket is the hole in the frame where the pedals install through. On an eBike, where the pedal installs is considered the center of the bottom bracket. So the SEAT TUBE LENGTH is measured from the middle of the bottom bracket to the top of the seat tube, where the seat post adjustment collar is.


5. Reach

xtracycle geometry

To find the reach on the bike, imagine there is a line drawn straight up from the middle of the bottom bracket. Then draw a line horizontally from the top of the top tube. The REACH is the distance from this top tub to where it intersects with the vertical line drawn from the bottom bracket. The reach is one way to measure how “long” a frame is.


6. Stack

xtracycle geometry

To find the stack on the bike, imagine there is a line drawn line horizontally from the top of the top tube. Then draw a line straight up from the middle of the bottom bracket. The STACK is the distance from bottom bracket to where it intersects with the horizontal line drawn from the top tub. The stack indicates how “tall” a frame is.


7. Effective top tube length

xtracycle geometry

The EFFECTIVE TO TUBE LENGTH is the horizontal distance from the top tube/head tube junction to the seat tube. This measurement has become significant as more and more bikes are designed with sloping top tubes. Effective top tube length is one of three options for defining the length of the front triangle.


8. Actual top tube length

xtracycle geometry

The ACTUAL TOP TUBE LENGTH is the length of the top tube measured from the center of the head tube to the center of the seat tube.


9. Step over height

xtracycle geometry

The STEP OVER HEIGHT is the length of a horizontal line measure from the ground to where the top tube meets the seat tube.


10. Chainstay length

xtracycle geometry

The CHAINSTAY LENGTH is measure from the center of the bottom bracket to the rear axle.


11. Deck length

xtracycle geometry

The DECK LENGTH is the length of the surface of the top of the rear deck.


12. Deck height

xtracycle geometry

The DECK HEIGHT is a vertical line measured from the ground to the top of the rear deck.


13. Wheelbase

xtracycle geometry

The WHEELBASE is the distance from the front axle to the rear axle.


14. Actual length
xtracycle geometry

The ACTUAL LENGTH of an Xtracycle is the distance from the front of the front wheel to the far most element on the bike. For the RFA, the far most element is the rear wheel. On the EdgeRunner and Stoker, the far most element is the rear tailpiece.