I am trying to get 20-30 mm of additional spread between saddle and bars, without increasing the stem length.

Does anyone know of an offset seat post that will allow me to position the saddle further back from the center of the post?

Ian

Pretty much any offset seat post will get you 20-25mm back... not sure if there are any that will go as far as 30mm.

Of course there are. I forget what there are called, but there are setback seatposts where the setback is measured in inches vs. millimeters. I wonder though if the o.p. really, really needs one. Most men's legs are accomodated well by the standard 25.4 setback on 'normal' seatposts along with the setback allowed for by 'normal' saddle rails.

I found an old used one on e-bay, had 30 - 35mm setback (vs 25 mm for most new ones). If not, you may need to consider a different saddle . . . there are pretty big differences between them into how far rearward you can go, depending on the exact placement and length of the rails.

Here: set back 40, Note, It aint cheap .. Nitto Lugged seat post 27.2 x 250 - 11048

Saddle adaptor pin assy, QSAPA. It requires a straight seatpost and an old-style seat clamp, each of which will cost a few bucks more (maybe a bunch less if you've got a local co-op) - but it will give you a lot of adjustment. If you need the setback, you'll probably be faster on this than on a much lighter high-end seatpost.

It's quite expensive, but the FSA K-Force is available in a setback of 32mm

VO Grand Cru, 30mm Seatposts - Components

How much setback does your current seatpost have?

25mm setback on a post is pretty standard. Zero offset posts are available and some seatposts come with35-40mm of offset. What's being measure here is from the centre of the seatpost to the CENTRE of the saddle clamps.

If you already have a standard seatpost with 25mm of setback it going to be near impossible to find a seatpost with a FURTHER 25mm of extra setback.
Something to keep in mind here is the width of the clamps. 2 different seatposts can have the same nominal setback but if one of the posts has narrower clamps it is possible to position the seat further back.

Anthony

Let me google that for you