Seatpost with setback vs in-line

kim10

Hi,
Not sure where to post so put it hear.
Just had a bike fit and hopefully my knee and hip problems will be a think of the past. A few things were tweaked during the fit and basically to get me in the correct position I ended up with my saddle as fare forward as allowed on the rail length. I currently have a FSA K-Force light seatpost with 25mm setback, and I’m just concerned that this forward position will put quite a lot of stress on both saddle and post. Also for aesthetic reasons it looks a bit odd or at least I don’t like it.
The guy that did the fit suggested having a try with an in-line seatpost (which we tried during the fit) to allow the saddle to sit in a more central position. I have never ridden one so could somebody please explain if there will be any difference to comfort or anything else to consider?

itsnotarace

You will be sat 25mm further forward obviously, you would need a 25mm longer stem to retain your existing reach to the bars. You may need to flip your stem, remove a spacer or go to one with a greater degree negative rise to retain the same stack height

markos1963

I got bikes with both but can't feel any difference between them. I can tell the difference between a carbon or ali seat post though.

styxd

You will be sat 25mm further forward obviously, you would need a 25mm longer stem to retain your existing reach to the bars, you may need to flip your stem, remove a spacer or go to one with a greater degree negative rise to retain the same stack height

They wont be sat 25mm further forward, read the first post properly.

Inline posts are fine, you could also try a post with a little less set back like a Thomson (think they are 15mm) or a USE (they are 10mm I think)

itsnotarace

markos1963 wrote:

I got bikes with both but can't feel any difference between them.

Assuming all else is equal, there is no difference apart from the setback. Setback just allows for different seat tube angles and is there to adjust the reach distance to the bars, same as stem length.

markos1963 wrote:

I can tell the difference between a carbon or ali seat post though.

Tyre pressures have a greater effect on comfort, but that's another topic

itsnotarace

styxd wrote:

They wont be sat 25mm further forward, read the first post properly.

Sorry, 25mm less the distance of the new rail adjustment. Rail adjustment isn't massive on most saddles though.

styxd

Setback just allows for different seat tube angles and is there to adjust the reach distance to the bars, same as stem length.

I think a set back post is there to put your hips in the correct place for pedalling rather than for adjusting the distance to the bars, thats what different length stems are for.

itsnotarace

styxd wrote:

Setback just allows for different seat tube angles and is there to adjust the reach distance to the bars, same as stem length.

I think a set back post is there to put your hips in the correct place for pedalling

That too, it's all linked as well as crank length, shoe size and even pedal stack height also contributes.

styxd

Its a bloody minefield!

thiscocks

styxd wrote:

You will be sat 25mm further forward obviously, you would need a 25mm longer stem to retain your existing reach to the bars, you may need to flip your stem, remove a spacer or go to one with a greater degree negative rise to retain the same stack height

They wont be sat 25mm further forward, read the first post properly.

Inline posts are fine, you could also try a post with a little less set back like a Thomson (think they are 15mm) or a USE (they are 10mm I think)

No they will be sitting 25mm further forward.

John.T

Kim10 wrote:

Hi,
Not sure where to post so put it hear.
Just had a bike fit and hopefully my knee and hip problems will be a think of the past. A few things were tweaked during the fit and basically to get me in the correct position I ended up with my saddle as fare forward as allowed on the rail length. I currently have a FSA K-Force light seatpost with 25mm setback, and I’m just concerned that this forward position will put quite a lot of stress on both saddle and post. Also for aesthetic reasons it looks a bit odd or at least I don’t like it.
The guy that did the fit suggested having a try with an in-line seatpost (which we tried during the fit) to allow the saddle to sit in a more central position. I have never ridden one so could somebody please explain if there will be any difference to comfort or anything else to consider?

Bloody hell. This is such a simple question.
Kim. You have had a bike fit and now know where your saddle needs to be relative to the BB. All a seat post does is hold it in the right position so you should use one that lets you do this without compromising the saddle rails. If an in-line one does this best then use one. If properly designed it will not feel any different from a set-back one.
This will have no affect on stem length or anything else if they were already right.

Evil Laugh

Jesus what a load of nonsense in this thread.

The saddle position re BB, like John said, is not moving. Changing the seatpost layback just changes where on the rails you are clamping the saddle. With a layback post at the back of the saddle rails, with an inline, at the front.

When the saddle is clamped right at the back of the rails like in the OP's case with a 25mm post, the saddle can feel flexy at the nose. Depends on the saddle somewhat. The San Marco Regal I have is horrible in this respect.

I've suffered from this dilemma myself, a 73.5 degree seat tube angle and my saddle setback position (distance of saddle behind BB) puts me near the uncomfortable end of using a 25mm layback post.

I found Bontrager do a range of 5mm and 20mm layback posts which could be a good compromise for you to try if an inline (0mm) clamps too far forward on your saddle and gives you the opposite problem. There's a few guys selling the xxx light carbon posts on ebay right now from around £30 to £50 depending on auction, which seems a good deal. I got a 20mm to alleviate my position somewhat and center rail the saddle some more.

All you have to do is look where your saddle is clamped now. If it was clamped 5, 20 or 25 mm further forward, which would be the most central? Go with that post IMO.

Evil Laugh

Ok just read there's 10mm and 15mm posts etc too, you have all the options you need then.

kim10

John.T and Evil Laugh - thanks for the info just what I hoped and needed. After having a second look at the saddle position I think I probably need one with about 10mm set back, so I'm off shopping (hopefully something nice in the sale!)
Only annoying thing is I have to part with the FSA which looked great on the bike (red and black colour)

John.T

Only annoying thing is I have to part with the FSA which looked great on the bike (red and black colour)

Function matters more than form.

Evil Laugh

Make sure you accurately record the position of the saddle before swapping if you've just had a fit. A weighted string/plumb line from the nose and some electrical tape to mark on the top tube works for me to record setback.

Spirit level on top of the saddle to get that right and then measure from base of nose to top tube to get saddle height.

I find if you're dealing with shorter distances than say saddle to bb, less room for error.

Someonene might have a better method but those mm adjustments make all the difference when getting the saddle bang on.

petemadoc

Sound advice from Evil Laugh and John.

Ignore the other comments.

I use and inline seatpost otherwise I have to have the saddle right on the end of the rails. I'm not sure how much difference it actually makes but I just don't want my saddle clamped so far forward on the rails, it would make sense that the little bit of bounce you get from the rails isn't as effective this way and the front could be too flexy.