Ensuring that your new bike is properly fit to you is an important step in preparing for your first ride.  Your Authorized Specialized Retailer will be able to provide a basic fit, ensuring that you are able to ride your bike comfortably and efficiently. Specialized also offers Retül Fit, a data-driven bicycle fitting tool designed to improve comfort, prevent injury, and increase performance.

Frame Geometry

The Aethos features identical fit and handling geometry as the Tarmac SL7. Detailed measurements can be found in the geometry chart:

Image of geometry table -click to enlarge

Adjust the saddle height

The correct saddle height is crucial for pedaling efficiency and comfort. Retül can help you estimate your Aethos bike size and saddle height here


A new Alpinist seatpost has been developed for the Aethos. The minimum seatpost insertion from the top of the seatpost collar is 75mm.  The maximum insertion is 215mm.  If the supplied seatpost does not meet these requirements for your appropriate saddle height, you may need a shorter or longer seatpost.

Image of seatpost insertion -click to enlarge


Adjust the reach

If your bike is the correct size, you should be able to comfortably reach the handlebars with your elbows slightly bent. Your bike saddle can move back and forth on the rails–start with it centered and fine tune as needed. A professional bike fitter will set this position to line up your knee with the pedal axle. You can also adjust your reach by raising or lowering your handlebar height, and by increasing or decreasing the length of your bike stem.


A maximum of 35mm of spacers may be placed beneath the stem.  The lightweight scalloped spacers may be used below the stem only.  A maximum of 5mm of solid spacers may be installed above the stem.

Image of headset spacers -click to enlarge