Dave Elcome said:
I have seen this suggested many times now, but have never understood why? can you explain please?
To my underastanding, there are two reasons, to get you further over the bottom bracket for increased power output and to help open up your hip angle to avoid too much loss of power when you are in an aero tuck possition.
Have a look at Tri and TT bikes and the angle the seat tube is, vs a road bike, you will notice it is closer to the vertical. You can emulate this seat angle by using a "fast forward" seatpost, which is like an inverse set back seatpost (google it for detail) or by pushing your seat right forward on the rails.
Dont forget that when you push your seat forward, you close the distance between the bottom bracket and your seat so you may need to inch the seat up a bit. You may also need to alter the fore and aft possitions to optomise your hip angle.
In a TT while "comfort" is an aspect of fit, it should be "comfort" in the context that you can complete the TT distance while keeping your possition and form and not be shifting about out all over your saddle and having to change your riding possition all the time, not "comfort" in that you could ride the bike around all day, hence some of the set up on the TT bike will seem odd because they go against standard accepted road bike set up. In context, most times your going to be flying over 10-25 mile on this thing, not riding a hilly mountain stage race that will have you in the saddle 6-8 hours.
There are some longer TT distances and events such as Ironman distance Triathlon, not sure how they would set up, maybe they make compromises in terms of aero and power output for comfort since its a longer distance?