To adjust your seat height, you use a metric hexagonal wrench set. The hexagonal bolt is located on the bicycle frame at the bottom of the seat post. When you loosen it off you can then move the saddle when applying a small amount of force. If you loosen it too much you will lose your current saddle height setting.
So, try to avoid this unless you’ll need to start your saddle height tuning from scratch. Adjusting your saddle height will take a little trial and error to get right. Gradually raise or lower the saddle and ride the bicycle for a few moments to check if it is at a comfortable height.
To get a rough starting point for the correct saddle height, place your heels on the pedals and rotate the pedals backwards, ensuring that your hips are not rocking from side to side to reach each pedal as you rotate your feet. To do this, you can ask someone to hold you on the bike to take your balance, or you can set yourself up in a home trainer.
For a more accurate and advanced method to getting the correct seat height, and the method I use is to clip in both feet into your pedals and then measure the angle of your knee joint while each foot is at the most bottom of the stroke. It’s important that when you take this measurement that your feet are in a neutral, or flat, cycling position at the bottom of the stroke.
To do this method you’ll need someone to use a goniometer to measure the angle of your knee. The ideal angle is 27-37 degrees.
Illustrations sourced from bikefit.com
I personally prefer to error on the side of a lower seat. This is to enable me to get a good clean stroke through the bottom of the pedal stroke. I feel that this is important when climbing hills where you need to developed good power at low cadences.
One of the most common signs of an incorrectly set seat height is knee pain. If the seat is too high, then you’ll get knee pain at the back of your leg behind your knee. If the seat is too low, then you’ll get knee pain at the front of the knee just below the kneecap.
Continual saddle sores are also an indication of the seat being too high. This is due to the friction caused when rocking from side to side in order to get to the bottom of the stroke under load and at low cadences.
Now the saddle height is perfectly set, it’s time to get the seat level. This is the angle of the saddle with respect to the ground and its forward position (You can move the saddle forward or backward a few centimetres).
To adjust these two things, you’ll need to loosen the bolts located under the saddle, at the top of the seat post. Look under the saddle and you should find it easily. Here again, the same principle applies. Loosen the screw off slightly so that you can move the saddle.
When the bicycle is on flat ground the saddle angle should be almost parallel to it. I use a builder’s level across the top of the seat to check this. If you feel like you are slipping either backward or forward as you ride the bike you may need to adjust this.
The next step is to adjust your seat position forwards or backwards to get your knee in the right position over the pedal. The forwards or backwards position of the saddle is governed by your thigh length. To get the correct position drop a plumb line from the front of the knee through the pedal spindle.
Move the saddle forward or backwards to ensure that you get the plumb line drop through the pedal axle as shown below:
Illustration sourced from bikefit.com
By doing so you’ll be setting up the starting point of the forward or backwards position of your seat. You may need to make further minor backwards or forward adjustments to your seat to accommodate your riding style. Once it’s set up go out for a ride to check that it’s OK.
With any major adjustments to your bike, it’s important to take it easy the following two weeks to ride in the new position and ensure that you don’t cause yourself an injury. After the two weeks is up, you can start increasing the power you are putting into the bike.
Once you have your bike set up correctly you shouldn’t experience any pain or discomfort. If you are still experiencing any pain or discomfort then you’ll need to make further adjustments to address the issues.