How to Adjust Your Bike Seat
Having your bike seat adjusted to the right height is essential for a comfortable ride, efficient pedaling, and avoiding injury. Luckily, adjusting your seat is easy on almost all bikes, and you can make simple adjustments to get everything just right.
Adjusting Seat Height
1. Know that a seat at the correct height leads to comfortable, even pedal strokes. You know your seat is at the right height if you can keep your hips stable on the bike instead of rocking them back and forth to reach the bottom of the pedal stroke. When your foot is at the lowest point while pedaling, you want your knee to be slightly bent, not locked out completely straight or curved.
Your knee should be bent roughly 25 degrees. This feels similar to standing upright in an athletic position-- just a slight bend is enough.
If you do not have access to measuring tape, use this as your guideline for adjusting the seat height by hand: knee slightly bent, hips square while riding, and comfortable ability to pedal.
2. Measure your inseam. This is the distance from your crotch to the floor measured down the inside of your leg. To get an accurate inseam reading:
Hold the spine of a hardcover book under your crotch, mimicking the feeling of a seat.
Stand with your feet 6" apart.
Measure from the spine of the book to the floor. This is your inseam.
Multiply your inseam by 1.09. The resulting number will be the distance in inches that should be measured between the top of your bike seat and the axle of your pedals. For example: an inseam of 29 inches (73.7 cm), multiplied by 1.09 equals 31.6 inches (80.3 cm). So the top of your seat and the axle point of your pedals should be 31.6 inches (80.3 cm) apart. (This measurement can also be calculated with centimeters).
3. Learn how your seat post adjusts. All seat posts are loosened and adjusted at the junction where the seat post meets the bike frame. A quick-release lever at the base of the seat post can be pried opened and adjusted by hand. If there is a small bracket with a screw in it, you have a bolted seat post: use an Allen key or adjustable wrench to loosen the bolt just enough to move the seat post.
4. Adjust the seat height to your measured length. Gently slide the seat post up or down to reach your ideal measurement. It can help to nick the post at the right height, so you can find this adjustment again if the seat slips or someone borrows the bike.
5. Tighten the seat firmly. Either press the quick-release lever back down to its locked position, or re-tighten the bolts with your Allen key or adjustable wrench until there is no movement. You do not need to get it so tight that you can't undo it later. Basic hand tightness will be enough.
6. Check your measurement on a test ride. Head out into the driveway and go for a slow test ride. Make sure you can easily reach the pedals and get onto the bike, and you knees are not locked. Try standing while you pedal to make sure you can comfortably get out of the saddle. Make sure that the seat is facing straight ahead or your riding position will be awkward and uncomfortable.
Place the ball of your foot on the pedal when you ride. There should now be a slight bend (25 degrees) in your knee when the pedal is at its lowest point. This is your optimal seat height.
If you have clip pedals or cages, make sure you use them on your test ride -- they will affect your ride.
Everyone has a different body type -- your inseam measurement should be used as a starting point. You should then adjust the bike to fit you comfortably.
7. Troubleshoot any issues by moving the seat slightly up or down. If you have knee pain, the biggest cause is usually your seat height. Depending on what the pain is, you likely have different problems. However, if the pain does not go away with seat adjustments you should see a doctor.
If the pain is on the back of your knee, the seat is too high.
If the pain is on the front of your knee, the seat is too low.
Your hips should be sturdy, not rocking, while you pedal. If you slide your hips to each side with your pedal strokes, your seat is too high.
Adjusting Seat Placement
1. Know that the angle and forward position of a bike seat will affect your riding comfort. The height of your seat isn't the only thing that matters. Seats can be slid forward and backward and angled up or down to get rid of sore spots and make a more comfortable ride. To test for the perfect fore/aft position of the seat:
While riding, stop your feet so that one pedal is at 3:00 position (completely forward. Your foot should be flat.
Imagine a straight line coming down from the front of your knee to the ground.
This line should intersect through the middle of your pedal. In other words, your knee should be right over your pedal when in the 3:00 position.
2. Loosen the bolt underneath the seat to change forward/backward seat position. On the back of the seat, pointing down at the back wheel, is a small bolt that controls the seat placement. It connects to a bracket that clamps onto small metal tubes that hold the seat in place. Loosen this bolt by turning it counter-clockwise to lower the pressure on the clamps that keep the seat in place.
3. Make sure the seat is far enough forward for a comfortable ride. You should be able to comfortably reach your handlebars, and your knee should be over the pedal when your foot is at 3:00 in the pedal rotation. A good test is to try standing as you ride. If your seat is in the right position, you should be able to stand up easily without pulling or pushing on the handlebars. If you experience any of the following problems, slide the seat forward or back while the bolt is still loose:
Trouble standing, reaching for the bars, and finger numbness can mean the seat is too far back.
Trouble feeling comfortable down hills and shoulder pain can mean your seat is too far forward.
4. Make sure that your seat angle is level with the floor. Use a carpenter's level to make sure the seat is flat -- this evenly distributes your weight for more comfortable riding. That said, if you experience discomfort in your crotch you can adjust the seat a little, though no more than 3 degrees in either direction.
Women should typically tilt the seat slightly down for more comfort.
Men should typically tilt the seat slightly up for more comfort.
5. Loosen the bolts on the side of the seat to change the seat angle. This bolt, usually on the right of the seat, allows you to easily change the angle of the seat and then tighten it in place again. Some older seats have two small bolts underneath the seat, one in front of the seat post and one behind, that are needed to change the seat angle. You must tighten one side to push that side up while loosening the other, almost like a see-saw.
Never make large adjustments to your seat angle. Check you seat height and forward position first, then adjust the angle slightly, if at all.