Question: I’m confused. For years I’ve used Greg LeMond’s formula of multiplying crotch-to-floor distance by 0.883 to get saddle height, as measured from the center of the crank axle to the top of the saddle. My local bike shop used a goniometer (like a big protractor) to measure my knee angle at bottom dead center. Then they recommended a 1 cm increase in saddle height to achieve Andy Pruitt’s suggested 30-degree knee bend. I’m concerned, though, because it’s obvious that using the goniometer requires skill. Misaligning the tool could easily cause an incorrect reading. So should I trust Greg or the goniometer? — Madeleine G.
Coach Fred Matheny Replies: I agree that a goniometer takes experience to use correctly. Depending on the skill of the technician, it can produce widely different numbers for knee angle. The key to accuracy is finding the precise anatomical landmarks at the hip, knee and ankle.
But the LeMond formula can be deceiving, too, because of changes in the thickness of pedals, shoe soles and insoles since the multiplier was derived in the late 1980s.
For comparison, my crotch-to-floor measurement using one popular sizing system is 88 cm, which means I should set my saddle at 77.4 cm (including a correction for Look pedals). But with Specialized road shoes, I actually set my saddle at 76.0 cm. This gives me a knee bend right at 30 degrees as measured by Andy Pruitt himself. If I used Shimano’s SPD-SL pedals, the saddle would need to come down another 3 mm.
A problem arises because the goniometer method (as well as the LeMond formula) is a “static” measurement done while the rider sits still on the bike. Things change during pedaling, and this can alter the ideal saddle height. Other variables are foot length and how feet are angled during the pedalstroke (i.e., toes pointed down, up or horizontal).
Bottom line: Find the saddle height that works best for you by first establishing it with a sound formula, then changing it if a bit higher or lower gives you more cruising efficiency or power, depending on what’s important to the way you ride.
I’m not sure if I’ve ever used Greg Lemond’s formula for setting seat height or frame size? I’ve ben riding a 57/58cm, traditional geometry frame for roughy 40 years, and it’s the size that I use to race on in the mid 80’s, the same time frame that Lemond was racing.
I’m looking into this now because I’m on the prowl for a Colnago C40, and they are hard to come by in the size that I normally use, that being a 58cm c-t. I’ve come across a NOS C40 in a 55cm so I’ve set out to find information that could shed light on whether it’s too small or in the ball park? Finding a built up 55cm in traditional geometry is tricky as so many manufacturers are making slopping frames now. And, the frame in question is no where near where I live. I’d have to order it and have it shipped.
Today, I came across Lemond’s formula for frame size, which comes from his 1987 ebook, “The Complete Book of Cycling”. The formula was developed by him and Cyrille Guimard and goes like this: your inseam in cm x .667 = the correct frame size in cm. My inseam is roughly 32″, which is 81.28 x .667 = 54.21cm. That’s as close to a 55 as damn is to swearing! However, it also is a departure from what I have been riding for decades. Any thoughts are welcome.
Regards, Jared Purdy
Because everyone’s Femur (knee to hip) to Tibia (knee to ankle) measurements & thus ratio is different, using Lemond’s formula adjusted for thickness of your riding shoe sole can serve as a basic starting point for determining frame size & saddle height, which is best fine tuned by having someone follow along as you ride to observe your hip movement while pedaling. If your hips are rocking at all the saddle is too high. If knees angle is too great at the bottom of the pedal stroke the saddle is to low. Adjusting saddle height 1/4” at a time & riding several miles on each setting using a range of cadence & pressure can help further custom tailor the best saddle height for you. Over hundreds of miles further adjustments may be required for both saddle height & fore-aft positioning, depending on the type of bike & personal riding style, as well as any physical issues such as feelings of pain or stiffness. Bottom line: saddle adjustment is best fine tuned over time.
The problems with using formulas for figuring out anything is it’s too easy to end up using numbers that are wrong, which gives an incorrect result. I have always recommended and use this much more reliable method.
The easiest do-it-yourself seat-height adjustment is done on a trainer or indoors in a doorway and requires a helper. Put on your cycling shorts and shoes, mount your bike in the trainer or place your bike in the doorway, get on and hold onto the doorjamb to support yourself. Have your helper stand behind.
To find seat height, place your heels on the pedals and pedal backwards. You’ve found the optimum seat height when your legs are completely extended at the bottoms of the pedal strokes with your heels on the pedals. Have your helper watch for rocking hips, the sign that the seat is too high. Now, when you’re actually pedaling, you’ll have the perfect bend in your knees.
Hope this is helpful,
Jim