Taking a seat tube 27.0 -> 27.2?
 

I have an '86 Centurion Ironman (the red and white one) that I've put modern components on. Wheels and drivetrain are now black, seatpost and cockpit are not. I think it would look better with all black components. The issue is the seatpost. I prefer two-bolt seatposts since I am anal about my saddle angle. I also need some setback. The bike takes a 27.0mm seatpost. I cannot find a black 27.0 two-bolt seatpost with setback--Thomson apparently only makes a 27.0 with zero setback, even if they did make at 27.0 with setback I am right on the edge of it not working with the way they angle the seatpost.

SO--to my question. I have heard one can ask a shop to ream out a seattube to go from 27.0 to 27.2 ID. On the scale of not an issue at all to a horrible idea, where is this? Frame is not a showpiece by any means, it gets ridden a lot, but by the same token I would be sad if this lead to its demise.

EDIT: also just curious: *why* is this bike 27.0? Is that just how Tange tubing of the time was? This has the Tange No. 1

EDIT #2 : just more context as to why I'm asking here....recently moved and so LBS and I are new to each other. I want to make sure I understand the risks if any, should they end up being the overconfident type.

IMO, it's a HORRIBLE idea. Don't mess with the frame.

If you can find a smaller diameter seat post, use a shim to fit the post to the frame.

Honestly and without question, I'd do the shim before removing metal.

Alternatively, I'd get a machinist to turn down the seat post and refinish it. Alternatively, do it yourself (even by sanding) and refinish the turned down section. Heck, done properly, there may be next to nothing to refinish.

Ok, thanks for the advice. Turning down a 27.2 is a good idea...I'd guess that at minimum the turned down part would be no longer black though right?

Hmm, maybe I could just get my current seatpost powder coated black? ...not sure how much thickness that would add.

I think its best to find the correct sized seatpost so that you avoid any damage or potential risk of malfunctioning.

Maybe find something silver in the correct size and throw a few bucks at your local powdercoat guy?

0.2mm is hardly anything to take off. It will be fine. You will then also have a nicely dimensioned seat tube (assuming the LBS does a decent job) unlike a lot of production bikes which often have seat slipping down issues.

O.P.
Find the post you want and insert to the desired height, mark it where you want the black paint to end, remove it and use a matt black industrial paint from Rustoleum....done.
Powdercoat will add thickness that you will need to sand off anyway.
Best, Ben

This. Tange #1 will easily work with reaming to 27.2.
In fact, my 87 Ironman Classic- like yours, but yellow and white- uses a 27.2 already, and did not require reaming or any sort of magic or fancy forcing for it to fit properly.

I won’t debate the merits of doing it.

To me the real issue is finding a competent mechanic with the right tool you can trust to do the job.

I’d exhaust all other ideas. Have you searched everywhere for the black two bolt? Is there a machine shop in your area that does anodizing or hydrographics or hydro dipping?

Here is a black Cannondale sport two bolt and has an angle so looks like lots of setback

https://www.ebay.com/itm/NOS-CANNOND...Cclp%3A2334524

Interesting...I was just looking at vintage-centurion.com, and I was wrong, mine is an ‘87 too. Funny, that site lists ‘89 as the first 27.2 year. So either it’s wrong, or someone reamed yours out, or a 27.2 happened to fit in your 27.0 tube.

thanks! That’s the only such seatpost I’ve ever seen. Unfortunately the listing says it’s missing a part.

Thanks, that certainly sounds like something I could manage, though I’m not sure I’d trust myself to paint it particularly nicely. Is this a spray paint you’re thinking of?

yes, and it’s not like I can go in and check out their tools—everywhere around me is still all curbside due to covid. However this makes me think I could try to find a local frame builder, who would certainly be competent to do this. I’m in Philly btw.

good idea, powder coating had been on my radar but not anodizing or hydro (actually I have not even heard of that)

If I were to do this I’d look to see if Stanley still works at D&Q over in Cherry Hill NJ. He coldest my Hetchins and built some killer wheels for me. I don’t know if Belinkey in Philly would do it or not.

CCP,
Scotchbrite pad to " lightly" scuff up the seat post.....hang the post up with wire or twine masking what you do not want paint on (seatbolts and saddle clamps etc).
Use very light coats (small bursts) and stay at least 10-12 inches away, if using a satin or matt paint you won't go wrong....just light coats not one heavy one.
No sweat, if you foul up wipe it off and try again....:thumb:
Rustoleum or Krylon are good rattle can spray paints.
Best, Ben
https://cimg3.ibsrv.net/gimg/bikefor...d16006f110.png
Krylon might have a "fan nozzle" making spraying easier....not as durable as P.C. but it's on a part that will not get a lot of touching, unless wrapping a chain around it!

it looks like D and Q the cycle shop is gone now (tho there is now a D and Q the ski/snowboard shop). I’ll try Bilenky, thanks again.

Thanks, once long ago I rattle canned a frame and it came out fine so this seems within my limited skill set...dumb question, but Scotchbrite pad as in something that scrubs one’s pots?

CCP,
No dumb questions...yes the ones we use to scrub pots and pans...if using an already used on be sure to clean the post after to get the cooking grease off.:D
Best, Ben

Fwiw, a 27.2 fits fine in my wife's Centurion Ironman.

When I got it, the post was frozen into the frame. I got it out with some help of a bench vise. After that, I loosely wrapped some 120grit sandpaper around a rod and spun it inside the frame with a drill for a few seconds to clean up the rust.

I assembled and adjusted the bike with a cheap 27.2 from my shelves while I was deciding which seat to give her. It was only on final assembly that I realized it was a 27.0 bike.

You should just try a 27.2 and see if it fits tightly. Don't get a super long one, that's just a lot of extra work. It's tight enough that frequent adjustment would be a bummer.

You could also try a ball hone, that did the trick for me on a frame.

There was a post recently (don't remember the thread) of a frame that got reamed slightly off line and went through the side of the seat tube.

Hmm you are the second person in this thread to note that a 27.2 has worked in a Centurion frame that is supposed to be 27.0. And, it is the case that I really have to crank down the seatpost bolt on mine to stop the 27.0 post from slipping...interesting...

Yeah sometimes people have an undersize post in a frame for years. I've seen it. The binder bolt will still hold the post up, but the ears that it holds together may be angled and the slot may be smushed. You should have a look at the slot and see what you think. Post a pic if you're not sure. If it looks like it's been smushed down, you can always pry it open gently.

Otherwise, it's not a bad job to ream a seat tube yourself. You will need a Chadwick & Trefethen adjustable reamer size #3 or a Cleveland size I (I as in the letter I). They can be had for around 30 bucks on Ebay if you're patient. Easier than messing with a shop. Easy tools to use, just set the blades to get a snug fit and then put an adjustable wrench on and turn. Drip some oil in there too. Watch a youtube video on reaming if you're feeling nervous. Remember we all did this our first time once and we all lived through it. Even René Herse had a first seat tube reaming experience. How do you get good at something if you don't do it? Metalworking is fun and empowering! Skills build upon other skills and your skillset will become more than the sum of its parts. And I'm guessing it's less work and money to buy a reamer and do it yourself than it is to go to a shop. You can barely get someone to look at a bike these days for the cost of a good used adjustable reamer.

You start down this road, though, you know you'll end up like me and Gugie and TenGrainBread and others on this forum. Bull goose loony. Plum crazy. Bonkers. One day, you'll wake up and your partner will have left you because of your stack of obscure bike tools you bought "because it's cheaper than going to the shop" and you'll be all alone with all the weirdos your newfound skills attract to your place.

It'll be worth it.

Is your username a reference to Twin Peaks?

Wow Bilenky wrote me right back and said they’d ream out the tube for 100 bucks. A little more than I was expecting but I suppose one pays for expertise and the time of a busy place. Confirms that if done right it’s an unproblematic alteration at least.

WHY.. not just have the 27.2 post turned to 27.0.............? That route only potentially ruins something of much less value.

As I am sure you know... sh*t happens.. that way it aint your frame.