I'm thinking of replacing the alloy seatpost on my CX bike with a carbon seatpost in the hopes to add some dampening.

The bike is a Cannondale SuperX and has a Cannondale C3 alloy 27.2mm x 300m seatpost. I already have the saddle pushed back most of the way, so I need to ensure I get a seatpost with at least the same setback.

So how do you measure it?

The standard setback measurement is from the axis of the post, horizontally back to the center of the cradle.

Thanks....

Of course after posting I did a search and found a number of posts telling me the same.

Just measured... 25mm offset.

Since you're now as far back as possible, look for more setback if possible. This will give you room for error, or if a new saddle wants to be farther back.

I think FSA makes a CF seatpost with 30-something mm of setback.

Just as an FWIW: I ride bikes with both aluminum and CF seatposts and don't really think CF adds anything noticeable to the "dampening". Setback and seat rails, I think, add more than the material of the seatpost, and tires many, many times more.

Just on the general topic of getting your butt farther back, I've found that the Selle AnAtomica saddle rails allow more range of setback than nearly any other saddle.

I've read that some at least of the Fizik models are as good in this respect, but I haven't tried one.

For a high-setback post, I use the Nitto S-84.

What you also want to know is how far back the forward edge of the seatclamp is. Not all seatposts are measured equally in that respect. That is what will determine how far back you can move a particular saddle. Set a straight edge along the front length of the post and measure to the leading edge of the clamp for the true setback that can be used compared to your present seatpost. Provided you can get you hands on various seatposts to measure that is.

+ the saddle rail factors in, shape & length of that adjustment..


check these out https://www.ergon-bike.com/en/product...tzen#cf-series

Lower one is even the 'set back' model.

Make sure you consider
the saddle rail factors in, shape & length of that adjustment..
and it is the right width for you body frame.

After years of trial and error I determined that I need my saddle pretty far back to achieve optimal pedaling. My knee ends up behind the pedal spindle. When searching for seatposts, this is the one I decided on (I wanted a nice aluminum post.)

VO Grand Cru Long Setback Seatpost MKII, Silver - Seatposts - Components

I have one of those too. It's a beautiful seatpost and high quality. I love the VO stuff that I've seen.

I have the same issue needing my saddle pretty far back. I'm not sure if it's femur length or just personal preference. I do have "long legs" (cycling inseam) compared to my overall height. I'm a tad shy of 5'8" and my cycling inseam is about 32.5". I'm not sure if it's the femur, but based on the amount of setback I need, I suspect it is at least part of it.

All I know is that it just feels better if my knee is well behind "KOPS". I do use KOPS when setting up a bike just because it's a handy landmark to go from. That's how I did it: I started adjusting my bikes to KOPS when I learned of it and then just experimented and found everything, including my butt, shoulders and hands, felt better behind KOPS.

The rest of my body would actually prefer to be further forward. I think my arms must be short because reach to the bars is often an issue for me. I have to put short stems on most of my bikes. But my legs require the setback.

I discovered my saddle setback by accident when I tried setting up a new commuter bike exactly the same as my old one, which fits me better than any bike I've ever had. When I tried riding the new bike I could barely put any power into the pedals! It was terrible. After lots of careful measurements with a plumb bob I figured out that the seat tube angle on my new bike was significantly steeper, putting the saddle further forward even though it appeared to be in the same position. Moving it back fixed the problem.

I wonder how many bikes I've gotten rid of over the years because they didn't feel right or felt slow, but only felt that way because my saddle was in the wrong position.

I tend to like a short-ish reach too. I use short reach bars and a 90 - 100 mm stem on 54.5 cm top tube bikes, depending on the seat tube angle.

Yea, one of the handiest "duh" things I learned, probably on this or another forum, was how the STA affects saddle position and reach to the bars. Thus the adage: adjust your saddle position first then the reach.