The Thudbuster DT FS. (See pix)

I could not even approach my normal riding position with the stock DT FS seatpost (even with the seatpost in the illegal zone), so I decided to hacksaw the top of the stock seatpost off and telescopically add a 25.4 mm Thudbuster. The measurements, and a test with a generic 25.4 mm seatpost, indicated it should work ... and IT DOES!! I'm now very close to my road bike riding position on a DT FS, and both seatposts are well within the legal zone.

I cut the stock seatpost close to the top, hoping to keep the solid part, and was successful. The solid end would become the new seatpost base. What was the seatpost base became the top (giving a true fit for the new seat collar). I slit the seatpost (see pix), filed a V at the top of the slit to allow more compression, put on a Pyramid 31.8 mm seat collar (had to tighten it considerably, but it tightened up just fine), inserted the 25.4 mm Thudbuster ($88 from eBay), and dialed it it. What a difference between being cramped and having a full roadie position.

The results ... I put a fav road seat, a Xenon, on the DT FS TB ("DFT"), and went out looking for bumps. The ride is terrific, but I had some trouble separating the elation of having my roadie position (at least the saddle to pedal part) and the feel of the better suspensiion. I can say there's more difference adding the TB than between a non-sus bike and an FS bike, e.g., between a Speed P8 or Helios P8 and a DT FS. In riding the "DFT", you feel the forks react, then the seat, then the swingarm, when hitting bumps. I'm a happy camper, and somewhat relieved that the purchase of the TB worked out. A non-sus 25.4 mm seat post would, of course, fit as well as the TB, but you wouldn't obtain the "steal me now" impact.

Yan, here's your improvement over the Speed TR.

That's pretty slick maunakea, but you gotta get a shot of the WHOLE bike as well. ;p

Did you have to adjust your stem length as well?

For want of better terms, "quill height" and "stem length" could both be better... but those are minor compared to getting the saddle to pedal distance fixed. Now I don't feel cramped, like riding a borrowed bike with a seat tube 8 cm too short ... which was the adjustment the TB let me make.

Plans are to find alu tubing that fits inside the handlepost, put a threadless stem atop the tubing, then some nice bars and trigger shifters. My glove size is XXL, I'm always unintentionally changing gears on short grip twist shifters.

That's great tinkering! Is it safe? I don't know much about the physics of seatposts, but doesn't it seem like the fatigue marks of each individual seatpost are irrelevant when you telescope them? (i.e. they're only 'safe' when your seatpost is a certain length, but when you add more length above it then the leverage is greater). Just curious--like I said, I'm no scientist.

Good point. More than half of each seat post is "inserted" rather than exposed, so I think the tower of power will be within the safety margin. IIRC, telescoping booms on heavy equipment (what an analogy) use the rule of half in, half out.

I''m no engineer, but you should also keep an eye out for the slit you cut for any signs of it enlarging. It's always better to drill a small hole at the deepest end of the proposed slit first, then cut to the hole that you drilled.

Good suggestion. Now done.

The greater seat height and the rear offset of the Thudbuster will increase bending loads on the lower post.

OTOH, the Thudbuster will reduce impact loads on the seatpost as well on your butt.

This is a great DIY, maunakea, but that seat looks super high. Are you an exceptionally tall guy?

For that photo, I think I put it at max, i.e., each seatpost was 50% exposed. It should accommodate a 36" inseam. My inseam is less, but still beyond the OE seatpost max.