A slightly higher seat position appears to be favoured by Triathlete’s however a lower position is preferred by road and MTB riders because of toeing and heeling the pedal which is part of the pedalling dynamics of having your feet attached to the pedals. MTB riders also need a bit more clearance for obstacles.
The maximum seat height is measured to the surface where the "sit bones" rest to the centre of the Bottom Bracket shown as (2) in the figure below.
We can measure for this height many ways however I use the Cyrille Guimard method and then check for accuracy with
Cyrille Guimard, the former director sportif of Hinault and LeMond &Claude Genzling. During the Tour de France of 1978 Method.
With your inseam measurement, multiply the figure by .883. The result will be your seat height (2) above. you’ll be able to set your correct saddle height, which will be ± a centimetre of it’s final place. This allows near full leg extension, with a slight bend in the leg at the bottom of the pedal stroke. The disadvantage of this method apart from relying on your measuring accuracy, is groin to hip joint variation, crank length and foot size and cleat stack variations, however the result is always very close.
LeMond recommends that you that might consider a slightly taller saddle height if you ride with your toes down and your heel raised. Most importantly, make any changes in saddle height gradually, and give your body time to adapt to the new position. See the Table.
My Childhood Method
There are a few different ways to do this. Jump on the bike while using a nearby wall or doorframe to balance yourself. Rather than putting the balls of your feet on the pedals, instead place your heels there. With the aid of a helper, seat post height is adjusted to allow a completely extended leg at the bottom of the pedal stroke when pedalling backwards. If your hips rock while pedalling, the seat is too high. If your knee is still bent when the pedal hits bottom, then the seat is too low. Upon completion of this exercise, you position your feet normally on the pedals. The disadvantage of this method is foot size, How the thickness variation between your heel and the bottom of your shoe to the foot pad to the bottom of the cleat and your "heel Toe" style.
The Billy Joe Shearsby Method
Jump on the bike while using a nearby wall or doorframe to balance yourself. With the aid of a helper, seat post height is adjusted to allow a completely extended leg at the bottom dead centre (BDC) of the pedal stroke (BDC) without pelvic rotation (very important) on each side you should be able to extend your he;
- Zero to one half cm for recreational riders (under 75 kms/week),
- One half to one cm for experienced riders (over 75 kms/week),
- One to one and one half cm for endurance cyclists (over 400 kms/week).
Modify these recommendations if your soles are considerably thicker at the cleat than at the heel. It can be difficult to make an accurate measurement without a mirror or friend to do a visual check of your heel and pedal at BDC. This formula takes into account Time and Look style cleats.
From these three best methods, you should result in a range of values within a cm of each other, which should be optimal for maximum pedalling leverage. Here are two more I don’t use because they are more difficult and less accurate than the aforementioned.
Nordeen-Snyder (1977)
In determining the optimal saddle height the use of oxygen was taken as a starting point. On the basis of experiments it was concluded that the ideal saddle height corresponded with 1.05 x trochanter height. However, this method does not mention if the thickness of the sole and the height of the pedals are taken into consideration. Depending on the pedal-shoe system that is used, notable differences in saddle height can occur ( illustration size 1). A practical disadvantage is that it is very difficult to determine the trochanter height. Other surveys based on the same method determined the saddle height at 1.09 of the inner leg length (Hamley & Thomas, 1967). The height of the seat can have a very significant impact on the efficiency of riding. In one study of short-term total power output, saddle height was optimised at 109% of the inseam length (the distance between the bone in the crotch and the ground, in bare feet). While the experiment was quite specific in focus and there is individual variation, on average an alteration of saddle height of only 4% affected power output by approximately 5%.
Homes, Pruitt & Walen, (1994)
Another method starts from the angle of the knee. When the pedal is in its lowest possible position, the knee should be able to bend 25 to 30 degrees (see left). This method is only applicable when a global indication of the saddle height suffices. However, other surveys make clear that an exact determination of the saddle height can have major energetic consequences.
Set Your leg at maximum extension to bend by 25 degrees. Less won’t allow your leg muscles to operate near maximum extension where they are most efficient, and more disrupts your pedalling stroke and the health of your knees as well. Similarly, if you rock back and forth in the saddle, the saddle is too high.
Optimal adjustment of the bicycle depends on more than one variable and these variables correlate and interrelate. Rider styles also differ from a tendency to pedal toe-down (Pedalling with the balls, e.g. Hinault), compared to heel-down (e.g. Merckx), and in some cases "to ankle": dropping your heels at the top of the stroke. The optimum seat height depends also upon the (preferred) pedalling style.
Gonzales and Hull (1989) are in favour of a multi-variable measuring method, because each individually conducted approach (as described in the methods above) is too limited and does not lead to an individual optimalisation we must rely on averaging methods and fine tuning over time. Once you get your position right, you can keep the information for other bikes you may ride in the future.
Note: Its better to be a 1 cm low than to set the seat too high. While the former can at most marginally reduce performance, the latter can be harmful.Mountain bikers who ride on rough trails may want to lower their seat just a little, as they spend a large amount of time out of the saddle, going over bumps.
