Saddle Fore/Aft Investigated

Lance runs his Madone with a 25mm layback seatost and Concor Saddle

Here is a lowdown on how each of these affects where you might place your saddle-

1. Femur length- Very simple, the longer the femur, the more layback you may need to maintain a balanced weight distribution on the bike.
2. Weight distribution- This is important to make sure that there is not too much pressure on the hands or the saddle; both of which can cause serious problems. The optimum perception of distribution lies around 60% weight on the saddle to 40% on the bars. Of course this might change based on the individual (this doesn’t apply to time trial position).
3. Handling- for a bike to have optimum handling (as judged by Keith Bontrager), the rider’s centre of gravity should be through the centre of the bottom bracket. Have a read of Keith Bontragers explanation on Sheldon Brown’s website below http://www.sheldonbrown.com/kops.html
4. Aerodynamics- for those looking for aerodynamic gains over comfort, handling, and possibly power, the seat is put further forward so that you are able to maintain a lower position for less flexibility.
5. Flexibility- The less flexible you are, the further forward your saddle needs to be placed to maintain power throughout the pedal stroke. Either that or you raise the handlebars. Think of when you make a really hard effort on the turbo or in a time trial and slide forward. You are trying you open up your hip angle for more efficient pedalling.
6. UCI Rules- Except for the most vertically challenged, riders are forced to keep their saddles on TT bikes 5cm behind the bottom bracket. This is why you see riders like Landis risking becoming impotent to search for that extra power and comfort- see the point above. Ideally they would move the saddles far enough forward that they can sit comfortably, as in triathlon. 
    

   

   Ouch! Landis in his famous 'praying mantis' position

7. Handlebar position- If you want to maintain the same weight distribution between your hands and saddle but have your handlebars further away, you must move your saddle back also. This is why most of the protour riders have their saddles rammed as far back as possible to complement their aggressive handlebar position. 
    

    

   

   A 35mm Setback 3T seatpost for Roger Hammond- not as extreme as it sounds though due to the limited range on the seatpost

Sorry to all of those looking for a self help guide! Knee over pedal axle generally gets you in the correct region of saddle layback providing you don’t pedal extremely heel down or up.

Make sure that you do not take any of these points individually as they need to be viewed as a whole. For example, don’t go putting your saddle really far forward because you are inflexible. You may have a more efficient pedal stroke, but the weight on your hands would then be unbearable and your saddle height too low! If I mentioned all the side effects of each factor, the article would be an extra thousand words.

There are other factors that I haven’t mentioned and I have only really touched on the subject, so please feel free to comment.

Happy Riding!

Alex Rasmussen's Track bikes have a very forward saddle position, presumably to accomadate for the unusual amount of drop, doesn't look comfortable