I don't know if Thompson sells the parts to the general public. (I could see them only selling to builders they know will do posts that will come back to haunt them.) TiCycles does far more than just bikes and have engineering skills in house.

Ben

Thomson used to sell replacement parts.

I've owned this frame since about 1984. This is not about the frame. And, you can't fit a bike to yourself by a book.

I've used the FSA K-force SB25 on all of my bikes for over 10 years. They work great and you can also get a 32mm setback model. It has a 2-bolt rocker style clamp that permits very small changes to the saddle angle. I always shop around to find a source that's selling for far less than MSRP.

The normal setback for most posts is 20-25mm. Needing a 25-32mm setback has nothing to do with a frame being too small. Smaller frames are often made with steeper seat tube angles that may require more setback on the post. The saddle rails also play a part in the need for a post with more setback.

You will be happy with the S-83 or the S-84.
Both are quality and the 2 bolt adjustment is one of the best.

Builders (like Ti cycles, near Portland) can custom make you a seatpost precisely to your needs.. best is of course going to cost more..

I was looking at solutions for greater setback without changing the seatpost. I came across old threads about the M2racer Power Module which gives you an extra 4cm of setback, but the company closed a long time ago.




So then I came across the Rinsten Spring from Ukraine, but made in China. It's a simple U shaped rail made out of spring steel which is supposed to serve as a form of suspension. Looks like you can get up to maybe 8cm of setback, but you'll get a lot of bounciness if you're that far back. Supposedly reviewers say it feels pretty good, but some people worry about it being too bouncy, or about too much lateral deflection and torsion. This might also cause the clamp to slip backwards. I thought maybe if you stuck a piece of TPU or rubber block between the upper and lower rails, you'll get some dampening. If you also clamp the open ends with a second set of clamps, you might get less torsion.
Here is a video:


It goes for $60, but there are some similar products on ebay or Amazon from Chinese sellers for $20, although I don't know who came first. One difference appears to the the angle between the upper and lower rails. Rinsten claims 8 degrees. Superimposing the product images, I estimate the Chinese versions are probably 10-12 degrees, so you might have problems not being able to level the saddle if you run out of tilt adjustment on your clamp. The smaller angle of the Rinsten might have a better chance of leveling. Rinsten started as a Kickstarter campaign, and they claimed that the first batch was bad and had to be tossed. I guess from poor manufacturing tolerances, probably non-parallel rails or spacing. So I don't know if the version from Chinese sellers would have a similar problem. Rinsten claims that their next batches were closely watched and checked for quality control.

Rinsten also seems to have only partially shipped units to the campaign backers. The latest update says in order to ship to the remaining backers, they need to sell 3 units for every 1 backer. But I guess if you're buying one from their website, they're probably happy to ship it to you.

https://rinsten.com/

One reviewer on Amazon for the Chinese version says it snapped while riding.
Oh, I found a thread on Bikeforums where someone tested a prototype of the Rinsten, but it broke after 800 miles.
Although the kickstarter page says they're testing different materials and doing stress tests, so the production version might use a different material than the prototype.
Rinsten saddle spring

I was thinking about using this on my Brooks because I'm 2-3cm too far forward. But I have sprung B17 Flyer Imperial, which already has some tilting deflection from the springs, in addition to my thudbuster, so I would only use these additional U springs on an unsprung saddle.

But anyway, if I were to use this, I'd set the clamp as far forward as possible and then back it off to achieve the desired setback, as the main purpose for me is for the setback and not for the suspension.



Above: Rinsten

Below: Chinese variations on Amazon and eBay

I made my own, an aggressive copy of the '80s style layback BMX seatpost.

I bet the fatigue life on that Rinsten thing is measured in minutes for anybody heavier than Tinkerbell.



-Kedosto

I spaced out in my previous post. (Guilty - didn't read most of this thread.) I have one of those steel Nitto posts. Best production post I have ever owned or ridden by a lot. They are gems. Beautifully built, very well thought out and a joy to set up and use. Bought it earlier thi8s spring to have a post I trusted completely on a wild gravel ride that would also mean the clamp would be well away from the seat's ti rail bends. After that ride, I pushed the seat forward an inch to reset the bike to a fix gear. So I have been fooling with that post a lot. And what a joy!

$160 vs $55? If the $55 post works for you, you will probably never regret it. Spend the $160 and you have a post for a lifetime. Worth it? Can't answer that. Now, my Peter Mooney finally has a post as good as the bike.

Ben

I’m glad you guys came back to this post with the wire solutions! I have tried an S 84 in a few situations and I like as much as Professor Mooney does. These wire spring devices suggest a solution to the stoker saddle for my ongoing tandem build, if coupled with a damper. If my favorite stoker isn’t happy, I’m not happy.

My need for setback: somehow I do not feel in balance on a bike unless my sit bones (widest portion of saddle) are about 27 cm back from a plumb line to the BB. I can only achieve this with Brooks products or my old Ideale 92 with a deep seat tube angle (71 degrees on my ‘50s Rudge) or a high-setback seat post. It’s better with the long rails on Selle AnAtomica or Specialized saddles, and not so good with the Rivet design, at least the one I bought.

I don’t think my frames are all too small though some are a little too French (high seat tube), but life has trade-offs. High seat tube angle today is 73 degrees in my size, and I know that requires a 30 or 35 mm seatpost setback. Many very desirable light vintage machines, like my Masi and Mondonico frames have angles greater than 75 degrees otherwise they fit well. And no, not all of those builders’ products were custom; such angles represent The Way They Thought Things Should Be. But it doesn’t usually work for me at least at my current level. If I finally become ready for stage racing maybe that will change (lol!).

Don't buy the Velo Orange. The front saddle clamp 5mm bolt isn't big enough to have acceptable fatigue life with rider weight on the saddle and stress cycles from road vibrations.

I broke the first one in 3415 miles shrinking from 185 to 154 pounds and finished that ride standing.

I replaced it with a higher grade bolt which broke in 1690 miles dropping to 140 pounds over that distance and had my wife pick me up.

I was using a saddle with carbon rails although that was not prohibited.

I recently picked up a Nitto S-84. Two things I don't love about it:

1. It weighs 400g almost exactly, not the 300g claimed on some sites.

2. The tilt adjustment range is narrow. What I'd consider a neutral tilt is nearly the furthest nose-up position available. (At least that's true on one particular WTB saddle.) If you like a real nose-up tilt you might not be able to achieve it.

Other facts about it: The setback is somewhere between 35mm and 40mm. It sets your wallet back too. It is at least shiny.

To those who said needing more setback is a symptom of having the wrong frame size: people's bodies are different shapes and we can't all afford custom frame geometries. I ride an old steel Bianchi road frame that really should be my size, it's a 56cm frame and I am 5'8" and a smidge. Its seat tube angle is 72 degrees, less steep than most. The stock seatpost has some setback, about 12mm, it's not zero setback. And yet: on the stock seatpost I had to slam the saddle all the way back on the rails (past "MAX") to almost reach KOPS. On the Nitto, I can hit KOPS and the seatpost clamp is within the non-warranty-voiding section of the rails. (I know KOPS is a "starting point" but I find it quite comfy.)

It would be great if you could easily get a 56cm frame with a 70 degree seat tube angle. But apart from heavy antique Schwinn Varsities and Continentals, such a geometry is rare. I'm happy about the Nitto despite its shortcomings, since it would let me fit almost any old road frame, so long as the seat tube inner diameter is 27.2mm. Even one with a more typical 73 degree seat tube angle should work.

Just FYI this thread is from 2019 and hasn't been active since then.