I bought my friend and I each a Forte Precision seatpost at Performance today because they were really cheap, and we both wanted new ones anyways. We both have Panasonic Sport 1000's, and I used a caliper to measure the post which came to 26.85mm, so I bought 26.8mm posts. I can't get the new post in! Sheldon Brown wrote that the DX-2000 uses a 26.6mm post but that uses a totally different tubeset. Anyone know what size I need?

26.6

Hmm. Thanks!

My friend finally got around to installing the 26.6 Kalloy seatpost...except it wouldn't fit. I'm going to try installing it on my bike sometime tonight, but the thing is my friend really needs a new post. Anyone have a clue? They're both Tange 900 tubesets.

measure the INSIDE OF THE FRAME TUBE with the caliper: make sure you rotate the caliper while holding tension, so you get an accurate measurement (use the inside measurement ears) then release tension, and read the dial/screen.

you can also use these for accurate inside measurements of tubes:
https://www1.mscdirect.com/CGI/NNSRIT...51690&PMT4NO=0

you stick the "T" head down the tube, and tighten the dial, then remove and measure with a caliper, for EXTREMELY accurate inside measurements.

For what it's worth, my Track 4000 uses 26.6 as well.

That uses Tange 1000 right?

If you measured at the top you wasted your time.

Top of the post or top of the seat tube? I took out the post and measured an average, all around, 26.85mm.

I'll return back after I try installing the post.

i can confirm that the DX2000 (tange 900) is 26.6 at some point. mine is similar vintage to igneous' track 4000.

I'll go check what size my sport 500 and 1000 have...

I got some weird readings but it appears to be around 26.1

edit: sport 1000 with 1020 tubing

Im sorry.
I thought you measure the top of the seat tube.

Track 4000 uses Tange 2.

hammer.

I just used my dial caliper...seems like the original seatpost is closer to 26 than 26.6. Oh well. I wonder why I originally measured 26.85...I used a digital caliper then!

Worst advice i've ever seeen.

https://www.sheldonbrown.com/stuck-seatposts.html

Tubeset model isn't necessarily going to determine SP size.

Step 1: Take bike to shop.
Step 2: Ask them to measure it using a SP gauge (Devo hat looking thing, pic somewhere on Sheldon) or by just trying cheap posts.
Step 3: Buy the size you actually need.

To do it with calipers you really have to measure all the way down as far as they will reach, even then it's better to just do it right.