15 juillet 2010

Saddle Height

Fred Matheny

What's the matter ? You want to be certain of your best saddle height but just about every expert you hear or formula you see produces a different number.

Of all the ways that your body fits your bike, saddle height is the most important. Get it right and you'll produce the most power that your heart, lungs and muscles can muster. You'll escape most of the injuries inherent in doing a repetitive motion (pedaling) for hours at a time. And you'll have the best chance of doing it all in comfort.

But while there's widespread agreement on a general saddle height "window," there's certainly no consensus on the ideal for any given rider.

[To illustrate below, Coach Fred Matheny used himself as a guinea pig and calculated his saddle height using 4 non-commercial methods. He's 5-foot-10 (1.77 m) and has a crotch-to-floor measurement of 34.6 inches (88 cm), which is relatively long for his height.]

How to Measure Your Legs
This is important because the crotch-to-floor distance is the key measurement in determining saddle height.

- Stand barefoot with your back to a wall. FFeet should be about 8 in. (20 cm) apart. - Put a carpenter's square or large thin boook or record album (remember those ?) between your legs. Snug it into your crotch with the same pressure you feel on a saddle. One edge of the carpenter's square should be flush against the wall, the other sticking out in front of you.

- Have your assistant measure from the top oof the square to the floor in centimeters (easier to work with than inches). This is your crotch-to-floor measurement. Note that this probably isn't the same as the inseam length of pants you buy.

Calculations
Now as an example, let's plug Coach Fred's 88-cm crotch-to-floor measurement into 4 at-home methods for determining saddle height to see what happens.

Heel-on-Pedal Method. With your bike level on a trainer, pedal until you've settled onto the saddle in your normal position. Then unclip your feet and put your heels on the pedals. Pedal slowly backwards. Your heels should just keep contact at the bottom of the stroke as your legs straighten, with no hip rocking necessary.

This is dependent on the thickness of the shoe sole and pedal body, so saddle height will change along with these factors. After setting his saddle this way, Fred measured from the middle of the crank axle along the seat tube to the top of the saddle and got 76.2 cm.

109% Formula. Multiply the crotch-to-floor measurement by 1.09. Set the saddle by measuring from the top of the saddle to the top of the pedal when the crankarm is straight down in the 6 o'clock position. This ancient formula gives Fred 95.9 cm, which results in a saddle more than 2 cm higher than method No. 1. Measured from the center of the crank axle along the seat tube to the top of the saddle, he got 78.6 cm.

LeMond Method. Greg LeMond says to multiply your crotch-to-floor measurement by 0.883. This figure was determined in the early 1980s by LeMond's French coach at that time, Cyrille Guimard. Back then, everyone was on cage pedals with toe clips and straps and wearing leather-sole shoes with nailed-on cleats. LeMond recommends subtracting 3 mm from the number produced by his formula if you use clipless pedals. Fred takes off another 2 mm because shoe soles have become thinner, too. Height is measured from the middle of the crank axle along the seat tube to the top of the saddle. Fred's result is a saddle height of 77.2 cm.

Pruitt Method. Andy Pruitt checks leg extension by using a large protractor-like instrument called a goniometer (illustration courtesy of Bikefit.com). It measures the angle of the knee when the pedal is at dead bottom center. He says saddle height is right when the bend is between 25 and 30 degrees. Fred's saddle height when his knee at DBC is bent 28 degrees: 77.0 cm.

Serotta SizeCycle. To get a value using a commercial system, Wheat Ridge Cyclery near Denver fit Fred on a popular bike fit device available to Serotta dealers. The SizeCycle recommends a saddle height of 77.0 cm.

Notice that while Pruitt's method agrees with the Serotta SizeCycle, those 2 recommendations are slightly lower the older methods. One reason is that new pedal systems and shoes put your feet closer to the pedal axle.

So where has Fred put his saddle, given the varying formulas? It's currently at 74.5 cm measured from the middle of the crank axle along the seat tube to the top of the saddle.

Why is this lower than all the recommendations ? Several reasons :

- Fred has moved his shoe cleats rearward inn recent years as a way to reduce "hot foot" on long rides. The cleats aren't all the way back, but they're perhaps a centimeter closer to the heel than they were when most of these saddle heights were calculated. Moving cleats back has the effect of shortening the leg/foot combination. Thus, it requires a lower saddle.

- He's using Shimano PD-7810 pedals ("Lance pedals"), which put feet closer to the pedal axle and again calls for a lower saddle.

- He has moved his seat rearward for more coomfort. The tip is now 6-7 cm behind the bottom bracket axle vs. about 5 cm before, depending on saddle model (he usually rides a Fizik Aliante).

- Finally, Fred says he feels more comfortabble and powerful with a slightly lower saddle. He first noticed this while riding his mountain bike. He lowered the saddle for ease in dismounting and greater agility while pedaling on technical terrain, and a byproduct was better climbing power.

What should you make of all this ? Use saddle height recommendations not as an end in themselves but as a basis for your experiments. You have a window to work in, as Fred's example illustrates. Use it and you'll arrive at your most efficient, comfortable and powerful position.

(Adapted from Coach Fred's Solutions to 150 Road Cycling Challenges, a helpful eBook especially for cycling newcomers.)


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