Setback/inline seatpost and 80 or 100mm stem.

daniel_b

If you had the choice (because you knew the distance was correct) between an inline seatpost teamed with a 100mm stem, or a 20mm setback post with an 80mm stem, which pairing would you choose and why?

Seatposts are both ritchey carbon wcs, and stems are both fsa sl carbon.

YIMan

I would have thought it depends on the geometry of your bike and your body and whatever gives you personally the best fit? While the reach is the same, the setback is altering your position over the bottom bracket/pedals.

UndercoverElephant

Depends on the rest of the geometry and where you're saddle rails would need to be to be correct. The (sometimes flawed, but usually quite good) way to check it to have your pedals at 3 and 9, seated on your saddle as usual, then a plumb-line held against the fleshy part under your knee should dangle and touch the top edge of your crank arm.

daniel_b

UndercoverElephant wrote:

Depends on the rest of the geometry and where you're saddle rails would need to be to be correct. The (sometimes flawed, but usually quite good) way to check it to have your pedals at 3 and 9, seated on your saddle as usual, then a plumb-line held against the fleshy part under your knee should dangle and touch the top edge of your crank arm.

Handy tip, is this known as KOPS?

rolf_f

Set back is decided by your leg length and stem by your torso/arm length. One of the two choices is likely to be right and one wrong. Therefore, I would choose whichever of the two choices actually fitted me in favour of the one that didn't!

The logical approach is to first determine the correct set back and saddle position and only then to worry about the stem.

UndercoverElephant

Daniel B wrote:

UndercoverElephant wrote:

Depends on the rest of the geometry and where you're saddle rails would need to be to be correct. The (sometimes flawed, but usually quite good) way to check it to have your pedals at 3 and 9, seated on your saddle as usual, then a plumb-line held against the fleshy part under your knee should dangle and touch the top edge of your crank arm.

Handy tip, is this known as KOPS?

Indeed, Knee Over Pedal Spindle. Works for some, not for others.

EKE_38BPM

UndercoverElephant wrote:

Daniel B wrote:

UndercoverElephant wrote:

Depends on the rest of the geometry and where you're saddle rails would need to be to be correct. The (sometimes flawed, but usually quite good) way to check it to have your pedals at 3 and 9, seated on your saddle as usual, then a plumb-line held against the fleshy part under your knee should dangle and touch the top edge of your crank arm.

Handy tip, is this known as KOPS?

Indeed, Knee Over Pedal Spindle. Works for some, not for others.

KOPS is rated and highly slated.
I've recently been adjusting my position and read articles by Steve Hogg and the great Mike Burrows. If Mike Burrows doesn't use it, I won't either.
After fitting a cyclist to their bike by whatever methods they use, sometime the knee is over the spindle, sometimes it isn't, but its not something that either Mike or Steve specifically aim for.

UndercoverElephant

Quite right, it's not always the case. In order to find the correct position for me I took the following steps:

1) video of myself pedalling, with my usual heel-drop motion.
2) measured the angle of my knee at full extension, adjusted saddle height so that it was no straighter than 30°
3) changed fore-aft to align knee and pedal spindle
4) changed stem so that the reach 'seemed right'
5) took loads of KOMs.

May not be perfect, but better than choosing a stem/post on a whim.

The Rookie

A weight weenie would go for the inline seatpost as it will be lighter than a setback by a greater margin than the 100mm will be heavier than the 80mm.

drlodge

Daniel B wrote:

If you had the choice (because you knew the distance was correct) between an inline seatpost teamed with a 100mm stem, or a 20mm setback post with an 80mm stem, which pairing would you choose and why?

Seatposts are both ritchey carbon wcs, and stems are both fsa sl carbon.

There is only one correct position for the saddle and hence amount of set back required, and it is independent of the stem length.

Choose your seat post to get your saddle into the right position, then see what stem length you need. I can't see myself ever needing an inline post, with a 74 deg seat tube I need nearer 35mm set back.