Originally Posted by
cubewheels
Huge impact depending on the riding condition.
A long 10% gradient climb for example is like riding with the saddle tilted 6 degrees more upward and with 6 degrees less seat tube angle (or few dozen millimeters of added set back). If your bike fit is optimal, you'll experience discomfort on a long 10% gradient climb. You'll find yourself pulling the handle bar and that will add to the effort of climbing.
A rather simple solution when you're coming up on a very long 10% gradient climb for example is stop at the beginning of the climb, adjust the saddle, add 6 degrees tilt downward and move the saddle forward around 20 to 30 millimeters. Climbing will feel significantly easier if you make such adjustments.
Of course when you reach the top of the climb or the hardest part is over, you should can then stop and restore your previous adjustments to the saddle.
One clever solution is use TT saddle like the ISM ones. You can sit on the nose of those saddles and the nose part is an optimal position for climbing (tilted down and positioned forward). You don't have to stop at the side of the road and make adjustments before a long climb.
I've always wondered about this. When you ride up a hill all the contact points remain in exactly the same relative orientation. So if you remain seated then your bike fit geometry does not change in the slightest. The only thing that actually changes is the direction in which gravity acts on your centre of mass i.e. there is a larger component of gravity pushing you rearward on the bike vs vertically downward. Obviously that in itself is a significant change, but I'm not sure it warrants a major change in saddle position. Especially not of the magnitude described above.
Anyway this winter I have had the benefit of training on a Wahoo Kickr Bike, which can tilt to simulate anything up to 20% gradients. Having experimented with both saddle fore-aft and saddle tilt I've come to the conclusion that it isn't worth changing either of them. Although I have to say my particular saddle (Fizik Argo Tempo) has a very pronounced tail kick-up starting from the middle of the saddle, which acts as an automatic back-stop when climbing. If I had a more traditional flat saddle I probably would tilt it downward for extensive climbing. But I wouldn't necessarily move the saddle forward unless the climb was so steep that I was struggling to stay centred on the bike - in which case I would be standing anyway.
What I have noticed is that I actually prefer my default bike fit when climbing moderate gradients in the 5-7% range. That's about the point where my hands are pretty much unweighted on the bars. On the flat I feel a little more pressure on my hands in the name of compromise between comfort and bar height.