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.