Finding the correct saddle height for your bike is critical for a good fit and healthy knees. Here are some popular methods. You’ll need to know your barefoot inseam for the first two. To calculate it, put a thin book between your legs with one side of the book against a wall. The book should exert firm pressure on your crotch. Remember to keep the book horizontal. Use a pencil to mark the wall at the top of the book. Measure the distance from the floor to this mark — that’s your inseam.
1). Multiply your barefoot inseam by 0.883. Adjust the saddle until the distance from the top of the saddle to the center of the bottom bracket is this length. This method is a good starting point for setting your saddle at the right height, but it doesn’t take into account the length of the crank arms, the shoes you wear or the pedals you use.
2). Using the same barefoot inseam length, multiply it by 1.09. This should be the distance from the top of the saddle to the pedal platform, when the pedal is at the bottom of its stroke, not when it is in line with the seat tube.
3). Put your bike on a trainer and get into your normal riding position. Put your heels on the pedals and back pedal. Raise the saddle height until you just start to rock side to side on the saddle, then back it down a tad. You can also just go for a ride on your bike to do this. With the sun at your back, you can watch your shadow to see when you start to rock.
I can pretty much guarantee if you try all three of these methods, you’ll come up with three different saddle heights. The third method, though, is the one that will probably get you on the way to a good fit faster than the other two. That’s because it’s addressing the “real” you on the bike. A measurement is just a number; it doesn’t know if your build is slight or your feet are big.
So start with the last method and set the saddle height. To tweak it from here, you’d be well advised to follow Andy Pruitt’s advice. He’s the hands down expert. When your pedal is at the bottom of the stroke he suggests a saddle height that will give your knee a bend of 150 – 155 degrees. Note that the angle of a perfectly straight leg would be 180 degrees. We want a slight bend to the knee. He uses anatomical landmarks to measure the angle, from the hip (greater trochanter) to the knee (lateral condyle) to the ankle (lateral malleolus). It’s tough for a novice to locate the landmarks accurately, so if you go this route, work with someone who can help you.
What you’re ultimately trying to achieve is a position that won’t tweak your knees, those precious commodities that put up with a lot from a cyclist. When they aren’t happy about the saddle height, they’ll give you a shout and you’d best heed it. If your knees hurt at the front, try raising the saddle a bit. If the back of your knees hurt, try lowering the saddle a bit.