If you’re a regular reader of this blog you’re probably aware of the fact that I’ve been recovering from an “overuse” knee injury for the past couple of months. The injury might be better described as an overuse/maladjustment knee injury; I’m convinced incorrect saddle adjustment, as well as overuse, played a role. As part of of the process of resolving the injury, I went back and took a very close look at the saddle height on all of my bikes and now feel confident that they’re consistently adjusted and very close to where they need to be. I’ve always known correct saddle height is important for long-term knee health, but it’s never been as clear to me as it is now, after going through this process.
In an earlier post I outlined some of the common methods for determining saddle height:
- LeMond Method – Adjust the saddle to a distance equal to your PBH* x .883, measured from the top of saddle to the center of the bottom-bracket
- Petersen Method – Adjust the saddle to a distance equal to your PBH x .873, measured from the top of saddle to the center of the bottom-bracket
- Hamley Method – Adjust the saddle to a distance equal to your PBH x 1.09, measured from the top of saddle to the pedaling surface (with the crank at bottom-dead-center inline with the seat tube)
- Holmes Method – Adjust the saddle so your knee is bent 25-35 degrees with the ball of your foot on the pedal (with the crank at bottom-dead-center inline with the seat tube)
My pubic bone height (PBH) is 88.5cm (34.84″). Using the LeMond and Petersen formulas, I come up with 30.77″ and 30.42″ respectively; these measurements are used to set the distance from the top of saddle to the center of the bottom-bracket. After doing a fair amount of experimentation, I’ve settled on just over 30.5″. The Holmes method, which uses the knee angle as a way of setting saddle height, closely corresponds to the LeMond and Petersen methods.
Crank length isn’t mentioned in regards to the LeMond and Petersen methods, but it needs to be considered since both methods use the bottom bracket to set saddle height without factoring in crank length. If you use either of these formulas, you’ll need to adjust the saddle up or down slightly to compensate for longer or shorter cranks. Most people are running 170-175mm cranks, so adjust the saddle up or down approximately .10-.20″ depending upon which crank you’re running.
Among the above methods, Hamley is the only one that gives a significantly different result. According to Hamley, my seat should be set nearly .75″ higher than what is indicated by the other formulas. Even though the Hamley method gives me what appears to be an incorrect result, I like the fact that it factors in crank length by setting the saddle height based upon the distance to the pedal surface.
By taking a few measurements and doing a little math, I determined that by modifying the Hamley formula from PBH x 1.09 to PBH x 1.07, you end up with a seat height nearly identical to what is indicated by the other methods. Modifying the Hamley method in this way puts it in line with the other methods while also taking into account crank length. This is probably the most accurate way to set saddle height short of employing a professional fitting service.
Once you’ve used one of these formulas to get your saddle within a safe range, listen to your body to determine if you need to make small adjustments. Conventional wisdom says pain in the front of the knee indicates a saddle that’s too low, and pain in the back of the knee indicates a saddle that’s too high. This has been consistent with my experience. Many people may find their saddles were too low prior to using these methods (Rivendell’s Grant Petersen says 80% of the riders they see have their saddles adjusted too low). If you’re one of these people, give yourself time to adjust to the new position; it will feel strange at first, but in the long run you’ll be doing your knees a favor.
*PBH – Pubic Bone Height. Read this for instructions on how to measure your PBH.