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Taking a seat tube 27.0 -> 27.2?

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Taking a seat tube 27.0 -> 27.2?

Old 09-20-20, 08:56 PM
  #26  
coffeecherrypie
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Originally Posted by scarlson View Post
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?
Oh, I am sure that the spec is 27.0, I have the original seatpost. And I have a different Centurion that is also 27.0. Didn’t mean to imply that maybe the bike was actually a 27.2, I just meant that there seems to be a track record of 27.2s fitting, maybe these seat tubes tend to run a little big?

Yes, name is a twin peaks reference!

It does sound fun to ream it, appreciate the expertise. Currently no space for this kind of thing but maybe in the future. I found a framebuilder willing to ream it for the time being, although they said they are backed up with work so I would wait until the winter to bring it to them (currently riding this bike).
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Old 09-20-20, 09:19 PM
  #27  
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Originally Posted by coffeecherrypie View Post
Oh, I am sure that the spec is 27.0, I have the original seatpost. And I have a different Centurion that is also 27.0. Didn’t mean to imply that maybe the bike was actually a 27.2, I just meant that there seems to be a track record of 27.2s fitting, maybe these seat tubes tend to run a little big?
That'd be a very loose tolerance. I kind of doubt it.

Yes, name is a twin peaks reference!
Let's rock!
Cooper
Cooper
Cooper
Damn fine television.

Currently no space for this kind of thing
How so? I believe you could do this job in a phone booth. Marie Kondo is a capitalist shill. Clutter is the sign of an active mind! Break free from big minimalism and treat yourself to a reamer. You can sell it again, after, if that makes you feel better. Or start charging all your friends $100 to ream their seat tubes, since apparently that is the going rate. I use my reamer for stems, too, if I need to make one fit 26.0 bars and it's a 25.0.
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Old 09-20-20, 09:26 PM
  #28  
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Originally Posted by scarlson View Post
Marie Kondo is a capitalist shill. Clutter is the sign of an active mind! Break free from big minimalism and treat yourself to a reamer.
It's really too bad this forum doesn't do signatures. This is brilliant!
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Old 09-20-20, 09:32 PM
  #29  
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Originally Posted by rosefarts View Post
It's really too bad this forum doesn't do signatures. This is brilliant!
Did that recently change? Is my signature grandfathered in?

Also, come visit me in Boston anytime and I'll take you on a tour of my junkpile.
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Old 09-20-20, 09:43 PM
  #30  
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Interesting. There are totally signatures here. I just always use my phone, and they aren't included on the mobile site.
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Old 09-21-20, 12:45 AM
  #31  
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Originally Posted by scarlson View Post
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.
The reason reaming it is better than sanding or building up a seatpost (but these are fine hacks and will probably work) is that you ideally want a very constant dimension. If the seatpost is gripped fairly evenly a long way down it doesn't slip and doesn't have to be done up super-tight. You're right very cheap large adjustable reamers are available on ebay. I have one which is made in India (perhaps with old British tools from the 1960s). It works well. I used it to ream a 31.6 seat-post on a new frame. Use a bit of oil, always turn clockwise even when retracting the tool, and advancing the tool by half a turn between reaming operations worked best for me. I kept going until the seatpost fit right.

Since 27.2 is a very standard size it's quite common for people to have the precision-made tool that does exactly that size (this is probably why adjustable reamers are so much cheaper-- they don't need to have so much precision). I have one of these as well. With that tool there's even less to go wrong. You just scooch it in with a bit of oil and you have a perfect fit. Don't forget to clean the swarf out of the inside of the seat tube. I use a bit of rag with string tied around it. Shove it down to the bottom with a rod and then pull it back up a few times.

My point is it's easy if you have the right tool and there's very little to go wrong which I think is what the OP was asking.
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Old 09-21-20, 07:39 AM
  #32  
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Originally Posted by scarlson View Post
That'd be a very loose tolerance. I kind of doubt it.


Let's rock!
Cooper
Cooper
Cooper
Damn fine television.


How so? I believe you could do this job in a phone booth. Marie Kondo is a capitalist shill. Clutter is the sign of an active mind! Break free from big minimalism and treat yourself to a reamer. You can sell it again, after, if that makes you feel better. Or start charging all your friends $100 to ream their seat tubes, since apparently that is the going rate. I use my reamer for stems, too, if I need to make one fit 26.0 bars and it's a 25.0.
Don't you need a workbench and a nice solid clamp and a way to clamp the frame without pinching it while you do the reaming? I don't have any of that at the moment and am an apartment dweller to boot. One day though!
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Old 09-21-20, 10:26 AM
  #33  
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I have a super long black Bontrager SSR seatpost. Two bolt clamp.

Postage and it's yours.

Confirmed to fit an Ironman.

Since you are a little shy on workshop, give me a length estimate and I'll even chop it before mailing.

Last edited by rosefarts; 09-21-20 at 10:30 AM.
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Old 09-21-20, 10:29 AM
  #34  
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Originally Posted by coffeecherrypie View Post
Don't you need a workbench and a nice solid clamp and a way to clamp the frame without pinching it while you do the reaming? I don't have any of that at the moment and am an apartment dweller to boot. One day though!
Nah, I just stand over the top tube facing backwards, bike resting on its wheels on the floor. I don't own a bicycle work stand. THAT I don't have space for. No reason to involve a workbench in this, although I guess I have an old door propped up on some legs that some might generously call a workbench. I also live in a crummy overpriced tiny apartment, and my neighbors really hate me, but it doesn't stop me.

Stuff a rag down the seat tube to collect the chips. I'm confident you could do this with the frame between your legs in a phone booth. Remember phone booths?

The reamer will guide itself as long as you don't set it to too large a diameter right away.
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Old 09-21-20, 11:56 AM
  #35  
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Originally Posted by scarlson View Post
I'm confident you could do this with the frame between your legs in a phone booth.
I'd want to see photos. Wait -- on second though, I wouldn't.

To the OP -- I would take @rosefarts up on his (?) offer, before altering a classic frame. Between an option you can undo and an option you can't, over what is mostly a cosmetic concern, the choice should be obvious.
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Old 09-21-20, 12:25 PM
  #36  
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Originally Posted by coffeecherrypie View Post
Don't you need a workbench and a nice solid clamp and a way to clamp the frame without pinching it while you do the reaming? I don't have any of that at the moment and am an apartment dweller to boot. One day though!
...here is the setup I used recently on a restoration of a 50's follis. It's pretty simple, but in this case requires a stand.
What seems missing from this discussion is the somewhat imprecise manufacturing of seat posts, and the historical fact that many of them are not sized exactly as marked.

So sometimes a 27.2 marked seat post actually measures smaller, like 27.1. And it's pretty important to figure out what the actual tube inner diameter is down in the seat tube, not up at th e post lug, which can get distorted by heat in manufacturing or by subsequent abuse, by the owner. Anyway, I usually just go with sanding down the larger post, as easier than reaming. But in this case the seat lug was ovalized, and the set tube was exactly 26.0 inside farther down.

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Old 09-22-20, 10:24 AM
  #37  
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Originally Posted by rosefarts View Post
I have a super long black Bontrager SSR seatpost. Two bolt clamp.

Postage and it's yours.

Confirmed to fit an Ironman.

Since you are a little shy on workshop, give me a length estimate and I'll even chop it before mailing.
That is a supremely generous offer, thank you so much....but I imagine that is a 27.2 post right? Notwithstanding that it fits an Ironman, I think cramming a 27.2 in there is going to be my last option. I think I will try Ben's rattle can suggestion, and then if I am not satisfied with the result I'll take the bike over to Bilenky in the winter to have them ream the seat tube, since I don't think there's much risk if they are the ones doing it. Appreciate the encouragement from others to do the reaming myself but I don't think that's in the cards.

Last edited by coffeecherrypie; 09-22-20 at 10:29 AM.
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Old 09-22-20, 10:28 AM
  #38  
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Originally Posted by 3alarmer View Post
<snip>
What seems missing from this discussion is the somewhat imprecise manufacturing of seat posts, and the historical fact that many of them are not sized exactly as marked.
<snip>
Good point. I am aware of this--I have checked the original seatpost, and the replacement seatpost I have in there now, and they are both quite close to 27.00 according to my calipers.
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Old 09-22-20, 01:17 PM
  #39  
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Originally Posted by scarlson View Post
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?
i routinely ream seat tubes. .2 millimetres is nothing. If the outside diameter is 28.6, 27.2 is a cinch.
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