Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Can you hone out a seat tube?

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Can you hone out a seat tube?

Old 01-17-08, 10:35 PM
  #1  
jberenyi
Senior Member
Thread Starter
 
jberenyi's Avatar
 
Join Date: Dec 2005
Location: West Haven, Utah
Posts: 518

Bikes: Lynskey Level 3 Custom, De Bernardi SLX, Felt F1C, Burley Duet Tandem

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Can you hone out a seat tube?

My De Bernardi frame takes a 27.0mm seat post. Is there a way to hone out the seat tube for a 27.2mm which is only .008 larger? Has anyone ever done this before?
jberenyi is offline  
Old 01-17-08, 10:48 PM
  #2  
bindibadgi
Member
 
bindibadgi's Avatar
 
Join Date: Jan 2008
Posts: 44

Bikes: Steel Avanti Hammer

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Can't you find a 27.0mm seat post? I really wouldn't want to be taking anything off the inside of the tube.

They are usually engineered without much leeway, and 0.1mm of thickness makes a big difference in strength, especially on a part which is taking your weight some of the time. Also, even if there is enough meat there, if you didn't get it perfectly centered (all the way down - and you'd need to go fairly deep) then you'd really be risking a very weak seat tube.
bindibadgi is offline  
Old 01-17-08, 11:00 PM
  #3  
Coyote2
Senior Member
 
Coyote2's Avatar
 
Join Date: Sep 2005
Posts: 2,393
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Don't try it.
Coyote2 is offline  
Old 01-17-08, 11:05 PM
  #4  
bassplayinbiker
Senior Member
 
Join Date: Jan 2005
Location: Kansas City
Posts: 658

Bikes: Diamondback centurion. Home built tandem

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
better you than me
bassplayinbiker is offline  
Old 01-17-08, 11:30 PM
  #5  
Sheldon Brown
Gone, but not forgotten
 
Sheldon Brown's Avatar
 
Join Date: Jul 2002
Location: Newtonville, Massachusetts
Posts: 2,301

Bikes: See: http://sheldonbrown.org/bicycles

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by jberenyi View Post
My De Bernardi frame takes a 27.0mm seat post. Is there a way to hone out the seat tube for a 27.2mm which is only .008 larger? Has anyone ever done this before?
Yes, it's done with an adjustable reamer and a fair amount of elbow grease. Better bike shops will have this (quite expensive) tool and know how to use it.

Sheldon ".1 mm" Brown
Sheldon Brown is offline  
Old 01-18-08, 12:38 AM
  #6  
Ben the bike
Junior Member
 
Join Date: Aug 2007
Location: Australia, Queensland, Mackay
Posts: 17

Bikes: ckt carbon track, pogliagi fixie, cell carbon road

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Adjustable reamer

Seat tubes are reamed to produce a good quality surface finish and a precision fit with manufactured seat tubes. A seat tube reamer for 27.2mm seat posts should be stocked by good bicycle mechanics or bike builders, or an adjustable reamer can be used.
Ben the bike is offline  
Old 01-18-08, 04:02 AM
  #7  
bindibadgi
Member
 
bindibadgi's Avatar
 
Join Date: Jan 2008
Posts: 44

Bikes: Steel Avanti Hammer

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Sheldon Brown View Post
Yes, it's done with an adjustable reamer and a fair amount of elbow grease. Better bike shops will have this (quite expensive) tool and know how to use it.

Sheldon ".1 mm" Brown
I take it back. If the master says it can be done, who am I to argue?

Nice to know actually, but I think I'd still rather find the right size seatpost if I could.
bindibadgi is offline  
Old 01-18-08, 04:19 AM
  #8  
Rowan
Senior Member
 
Join Date: Jun 2003
Posts: 16,738
Mentioned: 117 Post(s)
Tagged: 0 Thread(s)
Quoted: 1418 Post(s)
Liked 14 Times in 11 Posts
Barnett's Manual deals with this. If you can find the relevant illegal pdf...
Rowan is offline  
Old 01-18-08, 05:59 AM
  #9  
Wino Ryder
"Purgatory Central"
 
Wino Ryder's Avatar
 
Join Date: May 2005
Location: beautiful "Cypress Gardens" florida
Posts: 1,757
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
You're talking about permanently modifying (possibly ruining) a good frame just to accomodate a seatpost. I think i'd be more inclined to take an old 27.2 seatpost to a machine shop and have them mill it down.

just my thoughts.
Wino Ryder is offline  
Old 01-18-08, 08:02 AM
  #10  
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 31,408

Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!

Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 1112 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
As Sheldon has noted, it certainly can be done. Mechanically it's a pretty straight forward procedure with the right tools. However, assuming your frame is a high quality thin tube one, there is very little excess wall thickness and the reaming would have to be at least 75-100 mm deep. I wouldn't do it.

27.0 seatposts are readily available and probably less costly than having the frame modified. For example, Thompson's Elite and Ritchey's WCS seatpost are made in 27.0 and there are lots of others.
HillRider is offline  
Old 01-18-08, 11:50 AM
  #11  
neil0502
My bike's better than me!
 
neil0502's Avatar
 
Join Date: Feb 2005
Location: Northern Colorado
Posts: 2,041

Bikes: (2) Moots Vamoots, (1) Cannondale T2000 tourer, (1) Diamondback Response Comp mtb

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm in HillRider's camp:

I'm sure it can be done. I don't doubt that it's done relatively frequently.

I wouldn't do it to one of my bikes, though.

YMMV.
neil0502 is offline  
Old 01-18-08, 11:53 AM
  #12  
Sheldon Brown
Gone, but not forgotten
 
Sheldon Brown's Avatar
 
Join Date: Jul 2002
Location: Newtonville, Massachusetts
Posts: 2,301

Bikes: See: http://sheldonbrown.org/bicycles

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by HillRider View Post
As Sheldon has noted, it certainly can be done. Mechanically it's a pretty straight forward procedure with the right tools. However, assuming your frame is a high quality thin tube one, there is very little excess wall thickness and the reaming would have to be at least 75-100 mm deep. I wouldn't do it.

27.0 seatposts are readily available and probably less costly than having the frame modified. For example, Thompson's Elite and Ritchey's WCS seatpost are made in 27.0 and there are lots of others.
It's only a tenth of a millimeter!

Sheldon "Not A Thompson Fan" Brown
Code:
+----------------------------------------------------+
|  January 17 is the birthday of Benjamin Frannklin  |
|  In my opinion, he was the greatest human being    | 
|  who ever lived.                                   |
+----------------------------------------------------+
Sheldon Brown is offline  
Old 01-18-08, 11:54 AM
  #13  
tellyho
Your mom
 
Join Date: Aug 2006
Posts: 2,544
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I was forced to do it on my fixie frame, a Trek 420 dump rescue on which someone had overzealously clamped the binder. Didn't have to enlarge the whole tube, just take down a bump where the binder had been overtightened. I'm not sure I'd do it if I didn't have to, but it's doable.
tellyho is offline  
Old 01-18-08, 12:11 PM
  #14  
neil0502
My bike's better than me!
 
neil0502's Avatar
 
Join Date: Feb 2005
Location: Northern Colorado
Posts: 2,041

Bikes: (2) Moots Vamoots, (1) Cannondale T2000 tourer, (1) Diamondback Response Comp mtb

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Sheldon Brown View Post
It's only a tenth of a millimeter!
I guess my reservation, Sheldon, is that your average shop is ... well ... your average shop.

This seems like the kind of process with very little margin of error. Not knowing how abrasive the hones are, I'd be wondering how much damage could be done, by an inelegant push or pull, in a split second.
neil0502 is offline  
Old 01-18-08, 12:52 PM
  #15  
Sheldon Brown
Gone, but not forgotten
 
Sheldon Brown's Avatar
 
Join Date: Jul 2002
Location: Newtonville, Massachusetts
Posts: 2,301

Bikes: See: http://sheldonbrown.org/bicycles

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by neil0502 View Post
I guess my reservation, Sheldon, is that your average shop is ... well ... your average shop.

This seems like the kind of process with very little margin of error. Not knowing how abrasive the hones are, I'd be wondering how much damage could be done, by an inelegant push or pull, in a split second.
The proper tool for this is an adjustable reamer, a very precise, slow-cutting hand tool.

I agree that a power-driven hone would be inappropriate.



Sheldon "Reamer" Brown
Sheldon Brown is offline  
Old 01-18-08, 01:20 PM
  #16  
Thumpic 
Senior Member
 
Thumpic's Avatar
 
Join Date: Dec 2007
Location: The Sunny South
Posts: 1,913
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm confused....why wouldn't you just get the right part??....I did a quick search from Google and saw bunches.........
__________________
Thumpic....

Green is the new "CHEAP"
Thumpic is offline  
Old 01-18-08, 01:21 PM
  #17  
rmfnla
Senior Member
 
rmfnla's Avatar
 
Join Date: May 2005
Location: La La Land (We love it!)
Posts: 6,330

Bikes: Gilmour road, Curtlo road; both steel (of course)

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 268 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Sheldon Brown View Post
It's only a tenth of a millimeter!

Sheldon "Not A Thompson Fan" Brown
Code:
+----------------------------------------------------+
|  January 17 is the birthday of Benjamin Frannklin  |
|  In my opinion, he was the greatest human being    | 
|  who ever lived.                                   |
+----------------------------------------------------+
Exactly, and 27.2 posts are much more common than 27.0

I love the doomsayers who think removing a hair's breadth of metal is an invitation to catastrophe.
__________________
Today, I believe my jurisdiction ends here...
rmfnla is offline  
Old 01-18-08, 01:47 PM
  #18  
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 31,408

Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!

Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 1112 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
Originally Posted by rmfnla View Post
Exactly, and 27.2 posts are much more common than 27.0

I love the doomsayers who think removing a hair's breadth of metal is an invitation to catastrophe.
I'm not really a doomsayer and Sheldon is correct, it's only a 1/10 of a mm. However, thin wall steel tubes have walls as little as 0.5 to 0.7 mm thick in the butted ends. So that 0.1 mm means removing 15 to 20% of the total metal thickness. Here is an example from the Columbus Tubing web site:
http://www.columbustubi.com/eng/4_4_1.htm

On a cheaper, heavy wall frame I wouldn't hesitate to ream it to 27.2 but I wouldn't do it on thin wall, light weight frame.
HillRider is offline  
Old 01-18-08, 03:56 PM
  #19  
anti.team
Senior Member
 
anti.team's Avatar
 
Join Date: Dec 2007
Location: Ballard, WA
Posts: 150

Bikes: '98 Kona Kula, '8X Univega Sportour SS, '81 Trek 710

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm not really a doomsayer and Sheldon is correct, it's only a 1/10 of a mm. However, thin wall steel tubes have walls as little as 0.5 to 0.7 mm thick in the butted ends.
But a seat tube isn't .5 to .7mm is it? None that I can think of are that thin, seems like they are more like 1.0+ although I don't have a bike in front of me to look at.
anti.team is offline  
Old 01-18-08, 05:29 PM
  #20  
rmfnla
Senior Member
 
rmfnla's Avatar
 
Join Date: May 2005
Location: La La Land (We love it!)
Posts: 6,330

Bikes: Gilmour road, Curtlo road; both steel (of course)

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 268 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by HillRider View Post
I'm not really a doomsayer and Sheldon is correct, it's only a 1/10 of a mm. However, thin wall steel tubes have walls as little as 0.5 to 0.7 mm thick in the butted ends. So that 0.1 mm means removing 15 to 20% of the total metal thickness. Here is an example from the Columbus Tubing web site:
http://www.columbustubi.com/eng/4_4_1.htm

On a cheaper, heavy wall frame I wouldn't hesitate to ream it to 27.2 but I wouldn't do it on thin wall, light weight frame.
I hear you, HR; all I can say is I have done this numerous times (yes, on good frames) and never had a problem.
__________________
Today, I believe my jurisdiction ends here...
rmfnla is offline  
Old 01-18-08, 05:32 PM
  #21  
J T CUNNINGHAM
Senior Member
 
Join Date: Nov 2006
Location: TORONTO , ONT , CA
Posts: 813

Bikes: '86 AMBROSI / C RECORD. PINARELLO MONTELLO / FRAME, FORK.

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
We had better keep this thread quiet, the 'weight-weenies', myself included

will be getting 'ideas'!


Regards,
J T
J T CUNNINGHAM is offline  
Old 01-18-08, 06:43 PM
  #22  
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 31,408

Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!

Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 1112 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
Originally Posted by anti.team View Post
But a seat tube isn't .5 to .7mm is it? None that I can think of are that thin, seems like they are more like 1.0+ although I don't have a bike in front of me to look at.
Actually you do have the info in front of you. Follow the Columbus Tubing link I posted. Their Spirit tubeset seat tube is 0.5 mm wall at one end and 0.6 mm at the other.
HillRider is offline  
Old 01-18-08, 11:36 PM
  #23  
Sheldon Brown
Gone, but not forgotten
 
Sheldon Brown's Avatar
 
Join Date: Jul 2002
Location: Newtonville, Massachusetts
Posts: 2,301

Bikes: See: http://sheldonbrown.org/bicycles

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by HillRider View Post
I'm not really a doomsayer and Sheldon is correct, it's only a 1/10 of a mm. However, thin wall steel tubes have walls as little as 0.5 to 0.7 mm thick in the butted ends. So that 0.1 mm means removing 15 to 20% of the total metal thickness. Here is an example from the Columbus Tubing web site:
http://www.columbustubi.com/eng/4_4_1.htm

On a cheaper, heavy wall frame I wouldn't hesitate to ream it to 27.2 but I wouldn't do it on thin wall, light weight frame.
Tubing used for bikes is sized by outside diameter. Thin wall tubing has a bigger hole than thick wall tubing.

Steel seat tubes are generally 1 1/8" (28.6 mm) thick. Reaming one out to 27.2 leaves a wall thickness of (28.6 - 27.2)/2 = .7 mm.

Older French tubesets had 28 mm O.D. seat tubes. You wouldn't even want to go as large as a 27 mm seatpost with one of them. The old metric tubing is basically extinct, has been for years.

Sheldon "Do The Math" Brown
Sheldon Brown is offline  
Old 01-19-08, 08:11 AM
  #24  
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 31,408

Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!

Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 1112 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
Originally Posted by Sheldon Brown View Post
Tubing used for bikes is sized by outside diameter. Thin wall tubing has a bigger hole than thick wall tubing.

Steel seat tubes are generally 1 1/8" (28.6 mm) thick. Reaming one out to 27.2 leaves a wall thickness of (28.6 - 27.2)/2 = .7 mm.

Older French tubesets had 28 mm O.D. seat tubes. You wouldn't even want to go as large as a 27 mm seatpost with one of them. The old metric tubing is basically extinct, has been for years.

Sheldon "Do The Math" Brown
Excellent point and the Columbus Spirit tubing reference I showed appears to require a 27.4 mm seat post (28.6 - (2*.6) = 27.4) unless the builder brazes in a 0.1mm shim to allow a 27.2 mm seat post.

My point was that thin wall tubing has little excess material and just reaming out what seems to be a small amount can represent a fairly large fraction of the actual wall.
HillRider is offline  
Old 01-19-08, 01:14 PM
  #25  
Sheldon Brown
Gone, but not forgotten
 
Sheldon Brown's Avatar
 
Join Date: Jul 2002
Location: Newtonville, Massachusetts
Posts: 2,301

Bikes: See: http://sheldonbrown.org/bicycles

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by HillRider View Post
My point was that thin wall tubing has little excess material and just reaming out what seems to be a small amount can represent a fairly large fraction of the actual wall.
My point was that a frame that uses a 27 mm seatpost is not built with "thin wall tubing." ;-)

Sheldon "Numbers" Brown
Sheldon Brown is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.