Tool Fool - 27.2 seatpost solution

[lconley]

Cyclus holder and handle and 27.2 seat tube reamer (very sharp). For when you really, really want to put that 27.2 lugged seatpost in your 26.8 or 27.0 frame. This will be first put to work on my 27.0 Guv'nor and then my 27.0 Bombadil (already honed, but still tight). Less than $100, shipped from Germany. This is my birthday present to myself for my 66th Birthday.

Laing

Delray Beach FL

[st nick]

Thanks Laing. 

I'm glad to know about this tool.

I'm wondering about the pros and cons of changing a 26.8 or perhaps 26.6 which most of my bike are to a 27.2.

Well, I can think of several pros...

I just wouldn't want to mess the seat tube up if there are cons.

Paul in Dallas 

.

[Julian Westerhout]

Laing, 

Happy birthday!   :) 

I'd love to see a report on how you found the process once you've done it. easy to difficult, quality of result, etc. 

Thanks! 

Julian Westerhout

Bloomington, IL 

[Ed Fausto]

Hi Laing,
I also found a supplier from Europe and plan to purchase the Cyclus holder and handle and 27.2 seat tube reamer.

I plan to ream my 51 GBW from 26.8 to 27.2 so I could use Cane Creek Thudbuster ST Seatpost.
The Cane Creek Thudbuster has helped me continue cycling even with my chronic lower back pain.
Could you give some tips or techniques you learn when you reamed your bikes seatpost?
Thanks in advance.

Edgar

[Conway Bennett]

I called Dave wages at ellis cycles to ream my hunqapillar to 27.2 from 26.8, and he wouldn't be do it because of the risk of damaging the frame.  You may want to consult an expert before doing this.

[Richard Rose]

Certainly there are degrees of back pain. Mine required surgery. I installed a Thudbuster on my Jones SWB & it worked really good. When I replaced the Jones with long chainstay Riv’s (Clem & Gus) the need for Thudbuster disappeared. On a related note I was gifted a Redshift Shockstop stem which I have installed on my project bike dubbed “MTBuno” inspired by ROADuno. It works fantastically well. So perhaps the Redshift seatpost is worth consideration too.

Sent from my iPhone

On Nov 5, 2025, at 7:18 AM, Conway Bennett <captaincon...@gmail.com> wrote:

I called Dave wages at ellis cycles to ream my hunqapillar to 27.2 from 26.8, and he wouldn't be do it because of the risk of damaging the frame.  You may want to consult an expert before doing this.

--
You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bun...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/6ec83137-3313-4004-aa38-feb50980ab66n%40googlegroups.com.

[Rusty Click]

I'll echo Julians request as to an update when done.  I would like to do the same to my Atlantis.

Rusty

[Dan]

I wonder the same thing. 

I can’t help but feel that 0.2mm (27.2 > 26.8 is 0.4mm or 0.2mm each side) is a lot of seatpost wall to be removed. It would be up to a 20% reduction in wall thickness of the seat tube, possibly more?

[Guy Jett]

What about finding a machinist with a lath to reduce the diameter of the seatpost.  I know of one in Alameda, CA, Who just did this to a fork steerer tube just before he repaired a broken right rear dropout for me. He's also a frame builder. http://www.mikkelsenframes.com/

--

You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bun...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/e4b451c3-2881-4ca0-a1fc-1ed0ab7b3a9bn%40googlegroups.com.

Guy

[Ed Fausto]

"When I replaced the Jones with long chainstay Riv’s (Clem & Gus) the need for Thudbuster disappeared."

Hi Richard,

That is a very interesting observation.
I have not yet tried using my Gus on long rides and will try it out first.
Because of the long chainstay, the seat is more centered and would reduce the direct bounce in the seat.
I took a quick look at Redshift but unfortunately, they only have the 27.2 as smallest option.

Thanks again.

Edgar

[Garth]

A  27.2 ID of a 28.6 OD steel frame is completely normal. Tons of steel frames are like that. 27.2 is by far the most common post. Not only is that .7mm enough, you also have the lugs that reinforce the top of the seat tube. I see many of the current Riv models are taking 27.2 posts now. So they appear to be moving away from seemingly everything taking a 26.8 post !  From my recent web shopping, most any of the steel frame designer/contractors/sellers like VO, Crust and Soma all use 27.2 posts.  Only the oversized ST models take a larger post. That said, any steel frame that takes a 27.2 post you wouldn't even know if it was reamed from the manufacturer or not.

The Cyclus reaming tool is self guiding. It's modular, the silver part being the cutter. The initial black portion is to guide and center it in the seat tube. Anyone who has tapped a BB or reamed a head tube can do it. Even if you haven't there's some YT videos of people doing it.

[Ed Fausto]

Hi Garth,

Thanks for the advise on the Cyclus reaming tool.  I did not know that the black portion helps guide the tool and help it center.
I have been assembling my own bikes but this particular procedure is quite intimidating.
Will search of Yt videos to learn more.
Thanks.

[Laing Conley]

I am no expert, but I am adventurous enough to try things that I haven’t done before. I have been taking things apart since I was a young child and I am now approaching my 70th birthday. 

1. Lubricate the cutter, guide and the inside of the frame with light oil - WD40, 3in1 oil, knife honing oil, actual cutting oil, etc. 

2. Get the guide on the end of the cutter as close to the inner diameter of the seat tube as possible. I was starting with a 27.0 not a 26.8. I use aluminum HVAC duct tape, but just about any kind of tape will do. Do not wrap the tape in a spiral, that will change the center. If more than one layer is required, cut the tape for each full layer. A tiny gap at the end of the tape is preferable to any small amount of over lap. Position gaps away from each other, preferably evenly 2 gaps @ 180 deg, 3 gaps @ 120 deg, etc. This may take do redoing a few times, but tape is cheap. 

3. Determine the depth of cut required (seat post insertion depth plus a little extra for adjustability) and mark the tool with a piece of tape. The depth of cut will be from the bottom of the cutter (not the guide) to the bottom of the tape. When the bottom of the tape on the tool gets to the lowest point on the lug, you are done. 

4. Remove the crank and bottom bracket. 

5. Stuff some paper towels into the chainstays and downtube to prevent chips from getting into them. 

6. If you have a shop vac, rig the hose to the bottom bracket to vacuum the chips while you are cutting. 

7. Cut slowly, stop and check as you go to make sure that you are cutting straight. Keep the cutter clean. Clean and re- oil as necessary. 

8. After you are through cutting, clean the inside of the seat tube thoroughly. Any stray chips will cause rust. Automotive brake cleaner and plumbing pipe brushes(kind of like long baby bottle brushes) work. Coat hanger and paper towels if that is what you have works also. Check that the bottom of the cut is smooth. 

9. Recoat the inside of the tube - frame saver, Boeshield, etc. 

10. Reassemble. 

Hope that helps. 

Laing Conley

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/2766b73f-6443-40d8-bbaa-cf5fe420e687n%40googlegroups.com.

[Nick Payne]

On Friday, 7 November 2025 at 9:57:17 am UTC+11 Garth wrote:

A  27.2 ID of a 28.6 OD steel frame is completely normal. Tons of steel frames are like that. 27.2 is by far the most common post. Not only is that .7mm enough, you also have the lugs that reinforce the top of the seat tube. I see many of the current Riv models are taking 27.2 posts now. So they appear to be moving away from seemingly everything taking a 26.8 post

Yes, I was rather surprised when I bought an Appaloosa frame in 2020 and found that it didn't take a 27.2 seatpost, given that the three previous Rivs I'd owned all took 27.2. Anyway, I found that the 26.8 seatpost  supplied with the frame was a loose fit, as was an old Suntour XC Pro 26.8 seatpost that I had, and a good quality vernier caliper showed the internal seat tube diameter to be slightly over 26.8, so I bought a 27.0 S65 Nitto seatpost and used my adjustable reamer to make the 27.0 post a perfect sliding fit in the seat tube.

Nick Payne

[Laing Conley]

11. Loosen the clamp bolt, but not too much. Make sure that the original seatpost slides in and and out easily, but that the bolt is not loose. The idea is that the seat lug is round and at the original diameter, but not able to spread from the cutting forces. 

Also, if you clean with brake cleaner, wipe it off the paint immediately. 

Laing

--

You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bun...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/4630e605-2070-47e0-968d-23633ad8c78en%40googlegroups.com.

[Ed Fausto]

Hi Laing,

Thank you for taking the time to write down your process :-)

I would not have thought of using the tape on the guide to make it as close as possible to the existing diameter of the seat tube and if I understood correctly, it is a critical step to make the cut as straight as possible.

Both my Gus and MIT Atlantis are using 28.6 seatpost.

Regards,

Edgar