Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

Miyata seat post q

Old 09-21-08, 06:25 AM
  #1  
jlillie
Junior Member
Thread Starter
 
Join Date: Sep 2008
Posts: 11
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Miyata seat post q

I'm looking for some help with a vintage Miyata frame. The bike is a 1987 215 ST. This is the low low end touring model for that year. The bike did not come with a seat post. The posts that I happen to have lying around are to small to fit into frame by about .010 of inch. The opening in the frame is about 1.060.
the modern seat posts I have are all 1.070. Did they make smaller seat posts/frame openings back then?
Thanks for any help.

I'm rebuilding 2 vintage Miyatas. One for myself one for my daughter.
jlillie is offline  
Old 09-21-08, 06:50 AM
  #2  
SweetLou
Senior Member
 
SweetLou's Avatar
 
Join Date: Jul 2007
Posts: 2,114
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Seat posts come in many sizes. I am not sure what size is used for the Miyata 215. I think you should take to bike to your LBS, so that they can measure the seat tube and get the correct size seat post.
SweetLou is offline  
Old 09-21-08, 06:52 AM
  #3  
T-Mar
Senior Member
 
Join Date: Nov 2004
Posts: 17,818
Mentioned: 430 Post(s)
Tagged: 1 Thread(s)
Quoted: 2471 Post(s)
Likes: 0
Liked 58 Times in 54 Posts
Miyata's butted frames typically use 26.8mm (approx. 1.055") seatposts. During this period, Miyata manufactured their own tubesets and chose to use a double butted seat tube, unlike most other tubing manufacturers, who used single butted seat tubes. Single butted tubes are butted (i.e. thicker) only at the bottom of the tube, where it inserts into the bottom bracket shell, because of the higher stresses at that location. Miyata's extra butt at the top of the seat tube, means it uses a smaller seat post than most single butted tubes.

The advantage of having the extra butt, in conjunction with in-house tube manufacture, meant that Miyata could control the top butt diameter, so that they only had to stock one size of seatpost, regardless of the thickness of the un-butted section of the tube. Bicycle brands who used tubing with single butted seat tubes could also stock a single seat post size, but to do so they had to ream or hone the seat tube to size of the thinnest gauge tube, an operation which added extra cost. The only other major tubing manufactuer who regulalry used double butted seat tubes was Tange.
T-Mar is offline  
Old 09-21-08, 07:01 AM
  #4  
top506
Death fork? Naaaah!!
 
top506's Avatar
 
Join Date: Nov 2005
Location: The other Maine, north of RT 2
Posts: 4,567

Bikes: '71 Gitane Super Corsa, '73 Atala Giro d'Italia, '73 Schwinn Super Sport, '76 Viscount Aerospace Pro, '81 Miyata 710, '84 Ross Signature 290s, '85 Miele Gara, '87 Miyata 512, '89 Centurion Ironman, many more

Mentioned: 31 Post(s)
Tagged: 0 Thread(s)
Quoted: 274 Post(s)
Likes: 0
Liked 5 Times in 5 Posts
Concur with T-Mar. All 5 Miyatas that I've owned took 26.8mm seat posts.
Top
__________________
You know it's going to be a good day when the stem and seatpost come right out.

(looking for a picture and not seeing it? Thank the Photobucket fiasco.PM me and I'll link it up.)
top506 is offline  
Old 09-21-08, 08:13 AM
  #5  
Charles Wahl
Disraeli Gears
 
Charles Wahl's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 3,466
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 170 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
Originally Posted by top506 View Post
Concur with T-Mar. All 5 Miyatas that I've owned took 26.8mm seat posts.
Which OP's measured opening size corresponds to. 1.060" = just shy of 27 mm, and subtract 0.2 mm for clearance, you have 26.8.
Charles Wahl is offline  
Old 09-21-08, 11:10 AM
  #6  
OLDYELLR
My bikes became Vintage
 
OLDYELLR's Avatar
 
Join Date: Aug 2005
Location: Ontario, Canada
Posts: 1,118
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by top506 View Post
Concur with T-Mar. All 5 Miyatas that I've owned took 26.8mm seat posts.
Top
I have a mid-eighties ladies' Miyata 310 with the seat post stamped 26.7, about 220mm long. The sticker on the seat tube says "MIYATA Cr-Mo CHROME MOLYBDENUM DOUBLE BUTTED TUBES" but I don't have any gauges handy to see if the seat tube is butted at the top. The "upper downtube" on these frames joins the seat tube just below the mid-point. I expect ladies' frames are the exception to the rule.
OLDYELLR is offline  
Old 09-21-08, 11:36 AM
  #7  
unworthy1
Stop reading my posts!
 
unworthy1's Avatar
 
Join Date: Sep 2004
Posts: 10,243
Mentioned: 43 Post(s)
Tagged: 0 Thread(s)
Quoted: 347 Post(s)
Likes: 0
Liked 14 Times in 14 Posts
and if T-Mar's explanation isn't enough, Sheldon Brown's database of seatpost sizes shows every *steel* framed Miyata (except for 2) takes a 26.8 post.
The exceptions are 1:
a Mtn. bike and 2:
a 610 which takes a 26.7! (and has the exclamation mark indicating how rare a size that is! I have never seen a seatpost marked 26.7, he doesn't say if it's a female frame or not)
unworthy1 is offline  
Old 09-21-08, 05:36 PM
  #8  
leecycle
Senior Member
 
Join Date: Jul 2006
Location: Ontario
Posts: 282
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by OLDYELLR View Post
I have a mid-eighties ladies' Miyata 310 with the seat post stamped 26.7, about 220mm long. The sticker on the seat tube says "MIYATA Cr-Mo CHROME MOLYBDENUM DOUBLE BUTTED TUBES"
I have a 1984 men's Miyata 310 and the seat post is also stamped 26.7; very strange size.
leecycle is offline  
Old 09-22-08, 07:01 AM
  #9  
T-Mar
Senior Member
 
Join Date: Nov 2004
Posts: 17,818
Mentioned: 430 Post(s)
Tagged: 1 Thread(s)
Quoted: 2471 Post(s)
Likes: 0
Liked 58 Times in 54 Posts
Any any seat post ending in a odd number is rare. Seat posts are normally manufactured in even numbered, 0.2mm increments. A difference of 0.1mm from the 26.8mm standard is not significant, as the binder slot would only have to cinched an extra 0.3mm. I can only speculate on the reason for these odd sized posts, but I doubt the seat tube's top butt is 0.05mm thicker than the standard. More likely, the post was manufactured slightly undersize and rather than rework them the manufacturer stamped the true size, knowing than the difference would not affect fit or function. Knowing the Japanese approach to quality, I suspect they probably even notified Miyata and received approval before shipping the posts.
T-Mar is offline  
Old 09-22-08, 12:14 PM
  #10  
jlillie
Junior Member
Thread Starter
 
Join Date: Sep 2008
Posts: 11
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
26.8mm Roger that! Off to nashbar.....
Thanks guys.
jlillie is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Andrew R Stewart
Framebuilders
8
06-07-12 07:03 AM
Square & Compas
Recumbent
7
08-26-09 07:50 PM
rektrader
Fifty Plus (50+)
26
06-29-08 11:12 PM
dekindy
Electronics, Lighting, & Gadgets
1
12-25-07 02:03 PM
c0urt
Foo
3
08-18-07 10:58 AM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


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.