Seatpost Minimum Insertion
07-16-20, 03:09 AM
#1
Junior Member
Thread Starter
Seatpost Minimum Insertion
When seatpost manufacturers specify a minimum insertion line on their seatposts, is it at point A or B on the frame?
07-16-20, 04:15 AM
#3
Senior Member
Join Date: Jun 2014
Location: Ontario, Canada
Posts: 4,624
Bikes: iele Latina, Miele Suprema, Miele Uno LS, Miele Miele Beta, MMTB, Bianchi Model Unknown, Fiori Venezia, Fiori Napoli, VeloSport Adamas AX
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1324 Post(s)
Liked 927 Times
in
640 Posts
I'd have my minimum insertion mark inserted at least as far as the weld below 'B'. Cantilever force can snap off the protruding seattube if there's too much seat post above that weld and not enough below it. I've seen frames ruined because that section between what you have marked 'A' and 'B' broke off because there wasn't enough seatpost below it.
Cheers
Cheers
Likes For Miele Man:
07-16-20, 05:53 AM
#4
SE Wis
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,505
Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970
Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 2743 Post(s)
Liked 3,390 Times
in
2,053 Posts
If I wasn't at least half way through the top tube I'd be looking at a longer post.
More if I were big & strong
More if I were big & strong
07-16-20, 08:34 AM
#5
Banned
answer is C , bottom of the seat post at least in as far as the bottom of where the top tube joins the seat tube..
On my touring bike build I had a classic Campagnolo seatpost I wanted to use, since it was close to max ( because of sloping top tube)
I had a welder add a length of a common Kalloy seat post, that diameter, then get the weld bead machined down smooth..
On my touring bike build I had a classic Campagnolo seatpost I wanted to use, since it was close to max ( because of sloping top tube)
I had a welder add a length of a common Kalloy seat post, that diameter, then get the weld bead machined down smooth..
Likes For fietsbob:
07-16-20, 11:24 AM
#6
Clark W. Griswold
Join Date: Mar 2014
Location: ,location, location
Posts: 13,493
Bikes: Foundry Chilkoot Ti W/Ultegra Di2, Salsa Timberjack Ti, Cinelli Mash Work RandoCross Fun Time Machine, 1x9 XT Parts Hybrid, Co-Motion Cascadia, Specialized Langster, Phil Wood Apple VeloXS Frame (w/DA 7400), R+M Supercharger2 Rohloff, Habanero Ti 26
Mentioned: 54 Post(s)
Tagged: 0 Thread(s)
Quoted: 4342 Post(s)
Liked 3,978 Times
in
2,659 Posts
answer is C , bottom of the seat post at least in as far as the bottom of where the top tube joins the seat tube..
On my touring bike build I had a classic Campagnolo seatpost I wanted to use, since it was close to max ( because of sloping top tube)
I had a welder add a length of a common Kalloy seat post, that diameter, then get the weld bead machined down smooth..
On my touring bike build I had a classic Campagnolo seatpost I wanted to use, since it was close to max ( because of sloping top tube)
I had a welder add a length of a common Kalloy seat post, that diameter, then get the weld bead machined down smooth..
If you are a larger rider than get the seatpost in farther and get something of length.
07-16-20, 03:53 PM
#10
07-16-20, 04:26 PM
#11
Senior Member
When buying used bikes first thing to look at after evidence of front end damage is condition of seat lug. Or on a frame like one in top post, top of seat tube. They are very very frequently damaged from inadequate insertion. Back when all frames were sorta similar the rule was 6 to 7 cm inside the frame. Make that 2-1/2” to 3” if you can’t speak metric. Modern frames with sloping top tubes will have huge amounts of seatpost showing. Means you need more post inside frame. Frames break and bend at this point all the time. There is not ever any reason to skimp on seatpost insertion.
On old steel frames it was possible to do lots of bending and repair that damaged seat lug. Sometimes it would be worth it to get out the torch and some brass. Modern frames mostly they get scrapped. Anyone thinking about how little insertion they can get away with will soon be scrapping a frame. Plus medical bills.
On old steel frames it was possible to do lots of bending and repair that damaged seat lug. Sometimes it would be worth it to get out the torch and some brass. Modern frames mostly they get scrapped. Anyone thinking about how little insertion they can get away with will soon be scrapping a frame. Plus medical bills.
Likes For 63rickert:
07-16-20, 04:39 PM
#12
Banned
To be clear; the minimum insertion line on the seat post is to be at the B height ,
so the rest of the seatpost below that line is below that point?
How long is the length of that post below that minimum line ?
and as I offered above, it should be the spanning the miter width of the top tube .....
so the rest of the seatpost below that line is below that point?
How long is the length of that post below that minimum line ?
and as I offered above, it should be the spanning the miter width of the top tube .....
07-16-20, 04:39 PM
#13
Senior Member
Join Date: Sep 2009
Location: Up
Posts: 4,695
Bikes: Masi, Giant TCR, Eisentraut (retired), Jamis Aurora Elite, Zullo, Cannondale, 84 & 93 Stumpjumpers, Waterford, Tern D8, Bianchi, Gunner Roadie, Serotta, Serotta Duette, was gifted a Diamond Back
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 305 Post(s)
Liked 2,038 Times
in
604 Posts
07-16-20, 04:59 PM
#14
Senior Member
Join Date: Dec 2015
Location: Menomonee Falls, WI
Posts: 1,833
Bikes: 1984 Schwinn Supersport, 1988 Trek 400T, 1977 Trek TX900, 1982 Bianchi Champione del Mondo, 1978 Raleigh Supercourse, 1986 Trek 400 Elance, 1991 Waterford PDG OS Paramount, 1971 Schwinn Sports Tourer, 1985 Trek 670
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 604 Post(s)
Liked 1,063 Times
in
535 Posts
This is in chapter 10 of my Park Tool School instructor manual.
Tim
Tim
Likes For tkamd73:
07-17-20, 12:41 AM
#15
Junior Member
Thread Starter
07-17-20, 12:42 AM
#16
Junior Member
Thread Starter
07-17-20, 06:12 AM
#17
Senior Member
Join Date: May 2008
Location: Fredericksburg, Va
Posts: 9,579
Bikes: '65 Frejus TDF, '73 Bottecchia Giro d'Italia, '83 Colnago Superissimo, '84 Trek 610, '84 Trek 760, '88 Pinarello Veneto, '88 De Rosa Pro, '89 Pinarello Montello, '94 Burley Duet, 97 Specialized RockHopper, 2010 Langster, Tern Link D8
Mentioned: 73 Post(s)
Tagged: 0 Thread(s)
Quoted: 1607 Post(s)
Liked 2,216 Times
in
1,103 Posts
I measured two Campagnolo posts. Both, a Chorus Aero and a NR, measured 57mm (2.25:") from the top of the line to the end of the post. I believe that may be enough to get the end to the bottom of the seat lug. Your risk.
__________________
Bikes don't stand alone. They are two tired.
Bikes don't stand alone. They are two tired.
07-17-20, 09:57 AM
#18
Senior Member
Join Date: Dec 2015
Location: Menomonee Falls, WI
Posts: 1,833
Bikes: 1984 Schwinn Supersport, 1988 Trek 400T, 1977 Trek TX900, 1982 Bianchi Champione del Mondo, 1978 Raleigh Supercourse, 1986 Trek 400 Elance, 1991 Waterford PDG OS Paramount, 1971 Schwinn Sports Tourer, 1985 Trek 670
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 604 Post(s)
Liked 1,063 Times
in
535 Posts
07-17-20, 11:40 AM
#19
Senior Member
Join Date: Jun 2014
Location: Ontario, Canada
Posts: 4,624
Bikes: iele Latina, Miele Suprema, Miele Uno LS, Miele Miele Beta, MMTB, Bianchi Model Unknown, Fiori Venezia, Fiori Napoli, VeloSport Adamas AX
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1324 Post(s)
Liked 927 Times
in
640 Posts
Any seatpost that was inserted only to Point B would have a lot of leverage/torque on that part of the seattube that's above the toptube of the bike. The more seatpost above the toptube and the heavier the rider the more leverage/torque there is. Its a failure waiting to happen. I tell people to make sure that at least TWO INCHES of their seatpost is BELOW the top of their toptube. I'm glad you did that. Having a seattube break off on a long ride is unpleasane at bast dangerous to the rider, and often the ruination of the frame.
Cheers
Cheers
