Pushing your saddle forward help with fit

[cnighbor1]

a forum member posted this
Keep in mind that it's a 57 cm top tube with a seat tube angle of 72.5 degrees. You could push your saddle forward and be in the same position as a 56 cm top tube with a 73.5 degree STA.
wouldn't pushing your saddle forward result in a different position on your bicycle that would favor more spinning of the pedals more RMP use of higher gearing and more climbing ability
and pushing saddle rearward would be the opposite
So to size a frame size to fit you by moving forwards or rearwards results in a different approach to cycling
Yes?
No?

[MattTuck]

a forum member posted this

wouldn't pushing your saddle forward result in a different position on your bicycle that would favor more spinning of the pedals more RMP use of higher gearing and more climbing ability
and pushing saddle rearward would be the opposite
So to size a frame size to fit you by moving forwards or rearwards results in a different approach to cycling
Yes?
No?

If we're just talking about the relationship between bottom bracket and saddle, you have some play. You can achieve the same "effect" by moving the saddle forward as you would by increasing the seat tube angle.

Same in reverse. (in both cases, you may have to make adjustments to saddle height).

[stephenmarklay]

In my opinion, yes and no.

Yes it will change your front rear bias and your position relative to the bottom bracket will change.

If you look at at a TT bike with 76 or great STA you are right on top of the pedals. That is to get an aero position but its not for better spinning or efficiency. It does however make you fast due to cutting through the wind.

You could not run a 72.5 on that bike as the hip angle would get too large and your legs would not be able to easily pass one the top of the stroke.

Anyway, I like being behind the pedals as Lemond preached and Ed here on the forum. Ed shows how it can keep your hands from taking too much pressure too.

[fa63]

a forum member posted this

wouldn't pushing your saddle forward result in a different position on your bicycle that would favor more spinning of the pedals more RMP use of higher gearing and more climbing ability
and pushing saddle rearward would be the opposite
So to size a frame size to fit you by moving forwards or rearwards results in a different approach to cycling
Yes?
No?

I think what he meant was that to have the saddle in the same position relative to the BB with the bike with the 72.5 deg STA / 57 cm ETT, you would need to push the saddle forward 1 cm, assuming all else equal.

To think about a different way, you would use a seatpost with 15 mm setback on the 57/72.5 bike, and 25 mm setback on the 56/73.5 bike. The saddle would still be in the same position relative to the BB if you clamped the rails in the same position.

[Mark McM]

Like others said, for rider position relative to the BB, what matters is saddle setback (horizontal distance from the BB to the saddle). The saddle setback is achieved by a combination of seat tube angle, seatpost offset, and position of the rails on the seatpost. For the same setback, with a steep seat tube angle the saddle with be positioned further back on the seatpost, and with slacker seat tube angle the saddle would be positioned further forward on the seatpost.

By the use of different seatpost offsets and moving adjusting the saddle forward and back on its rails, you can achieve the same setback with a fairly wide range of seat tube angles. This is why the Stack & Reach system of frame measurement is far more effective at measuring frame size: There is usually far more relative adjustability of saddle position (height and setback) than there is with handlebar position on any given frame - Stack & Reach removes the seat tube length/angle from frame sizing, so you can get a more direct picture of the most important dimensions for frame fit.

[Mzilliox]

oops, misread the quote a bit

[fa63]

For what it is worth, a 57 ETT / 72.5 STA bike will fit essentially the same as a 56 ETT / 73.5 STA bike if the saddle is placed in the same position relative to the BB on both bikes. Same stem length and all.

[stephenmarklay]

For what it is worth, a 57 ETT / 72.5 STA bike will fit essentially the same as a 56 ETT / 73.5 STA bike if the saddle is placed in the same position relative to the BB on both bikes. Same stem length and all.

True but (since this is my size range I know) it would require no less than a 35mm setback post to achieve the proper setback. So it is not really practical in all cases.

[fa63]

If you need a 25 mm setback with a 72.5 deg STA, then yes. Most people don't have femurs that long though :) But you are right, it could be a limiting factor.

[stephenmarklay]

If you need a 25 mm setback with a 72.5 deg STA, then yes. Most people don't have femurs that long though :) But you are right, it could be a limiting factor.

Yep it makes fitting harder. I was ok until I figured out that getting behind the pedals makes sense. i also have a harder time getting pants to fit. 31/34

[unterhausen]

develop some system of being able to recreate a position and try it. I like having my seat a little higher and further forward than my usual position. It really feels much easier to spin instead of my usual habit of mashing. The problem is that my knees complain eventually. 1/8" higher, 1/4" forward makes a big difference for me.