Advertise on Bikeforums.net



User Tag List

Results 1 to 18 of 18
  1. #1
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Looong Forward Seatpost

    I am in the process of trying to adjust my road bike to a Tri bike and I am having a lot of trouble finding a seatpost that is both long and has enough forward offset. I need at least 30mm forward offset and I need at least a 350mm post. If possible I would like a 31.6 but I am willing to shim a 27.2 up to 31.6 if that is my only option. I can find short posts with enough offset or long posts with only a little offset, but can't find something with both.

    I have looked at setback posts and then spinning it around but I don't know which ones besides the Thomson is actually reversable. Although the Thomson is nice...16mm of offset just isn't going to get me where I need to be.

    Does anyone have any experience with posts that may work?

  2. #2
    moving target c0urt's Avatar
    Join Date
    Oct 2006
    Location
    birmingham, al
    My Bikes
    a masi speciale, and a kuota k-factor.
    Posts
    2,831
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    have you thought of a shorter handle bar stem first?
    how to tape your bars http://www.flickr.com/photos/89572419@N00/sets/72157629279270681/

  3. #3
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by c0urt View Post
    have you thought of a shorter handle bar stem first?
    That would do nothing to put me in a better Tri geometry for my lower body, plus make my steering more twitchy as I am already running a shorter stem at 100mm. I need to get my legs and lower body into a Tri geometry, hence forward seat post and also I would be running aero bars.

    The other issue is my current seat post is too short at 300mm, and then moving the saddle forward will just exaserbate that situation further, so that's why I need a longer one as well as a forward one.

    I am looking to get my effective seat tube geometry nearer to a 77-78 degrees as would be found on a Tri-bike up from the 73 or so degrees it is now. Needing a longer seatpost makes it tougher because you need a larger offset to accomodate it. I am on a properly sized frame, I am just all legs and so need that distance in the seatpost.

    So....I have done a lot of looking into it, working with several different LBS, and all of that. They all basically said I will have to do my research and find one myself cause they don't carry anything like that and wouldn't know where to get it. Unfortunately there are no Triathlon specializing shops in my area.

  4. #4
    Senior Member jetta-the-hut's Avatar
    Join Date
    Jul 2009
    Posts
    216
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    just keep in mine if you race the seat cant be 5cm past the center of the cranshaft arm, look for a profile design fast foward seat post, as far as length, i'm not sure what to say except it sounds like your bike is too small if you need that big of a seat post.

  5. #5
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jetta-the-hut View Post
    just keep in mine if you race the seat cant be 5cm past the center of the cranshaft arm, look for a profile design fast foward seat post, as far as length, i'm not sure what to say except it sounds like your bike is too small if you need that big of a seat post.
    The profile design fast forward is only a 300mm, too short. It would be perfect otherwise....essentially I want to find exactly that....but in a 350 rather than 300.

    As I said in my previous post, the bike is properly sized, I was sized at multiple LBS. I am all legs with a short torso, so I have to get a bike that the top tube fits me and run more seatpost, this is especially true with a forward position because as you put the saddle closer towards the BB you need to go higher to have the same distance away from it. I am not looking to go up at 90deg or anything like that, I just want to get from a road position to a normal, legal, established Tri geometry.

    So, the bike is the right size or as close to the right size you can get for someone in bad proportion, I have a 37" inseam but I have a very short torso for my height. Imagine the torso from a guy that's 5'10" and then prop that up on legs from a guy that's about 6'6" and you get me. I have tried a host of bikes in many different sizes and many different manufacturers, I have been to probably no less than 10 seperate bike shops, I have done all I could to find the right bike short of having a custom one built for me. I found the manufacturer who makes their bikes taller with shorter top tubes after comparing the geometries on bikes from at least 15 different bike manufacturers. I didn't randomly pick up whatever bike was around.

    So....no, I don't need a bigger bike, cause then the top tube will be too long and I will be overly stretched out and it will put my body in an even worse position. I got the tallest bike I could while keeping the top tube reasonable, I have already shortened the stem to get some size back there.....all that stuff has been done.

    Now, does anyone have any info about any of these seatposts....anything? Please don't suggest getting a different bike, or changing a stem, or any other thing....I would really really appreciate feedback about....seatposts.

  6. #6
    Senior Member jetta-the-hut's Avatar
    Join Date
    Jul 2009
    Posts
    216
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    31.6 mm 367mm setback bend,
    http://www.bikepartsusa.com/bikepart...D&category=316

    31.6 400mm
    http://www.bikepartsusa.com/bikepart...y&category=316

    another option:
    http://www.trisports.com/qurootrish.html

    the only thing I can suggest is getting one of these really long ones and have it bent or welded to the degrees you need. these also have the option on sliding the seat all the way foward to help with the position of your body.

    I'll look some more later but there are a few out there.
    Last edited by jetta-the-hut; 12-31-09 at 05:01 PM.

  7. #7
    Senior Member jetta-the-hut's Avatar
    Join Date
    Jul 2009
    Posts
    216
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

  8. #8
    moving target c0urt's Avatar
    Join Date
    Oct 2006
    Location
    birmingham, al
    My Bikes
    a masi speciale, and a kuota k-factor.
    Posts
    2,831
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I was a bit vague at first I apologize.
    I meant a longer post being flexxy and or snapping. A flexxy post is a weird feeling if you are used to a stiff bike, and one that breaks is just bad.
    how to tape your bars http://www.flickr.com/photos/89572419@N00/sets/72157629279270681/

  9. #9
    Senior Member Barchettaman's Avatar
    Join Date
    Oct 2008
    Location
    Frankfurt, Germany
    My Bikes
    Focus frankenbike trash find commuter, BP Stealth carbon monocoque TT bike, Leader 720 tt, Quantec CC Cyclosross build, Eddy Merckx Corsa Extra Columbus SLX road bike
    Posts
    1,119
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Custom seat post is the answer here I think.

    Get a cheap steel 31.6 post of the requisite length, cut out a wedge section and weld the bugger back up. Easily done and cheap too.

  10. #10
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    So I broke out the metric tape measure, plumb bob and the handy dandy calculator and did a little geometry.

    My bike as I measured it has a 73.29D seat tube angle, however as it sits it has a small setback in the seatpost, so measuring at full extension on a 300mm seatpost from the bottom bracket to the clamp location at the rails I have an effective angle of 72.17 degrees. The post has about a 15mm setback which gives the clamp a location 245mm back and 800mm from the rails to BB. Just to answer the quick question...yeah I tried reversing it and I was sad to say it wouldn't work, couldn't get the saddle angle anywhere near ride-able.

    I slid the seatpost out past the min insersion line just to get a feel for what total distance I need, taking into account saddle height and all of that I need another 25-30mm distance away from the BB. Using that number I can then mark where my seat post must insert to (below the weld at the bottom of the top tube and seat stays on the seat tube. From there I set up a line showing 80 degrees the maximum angle one would use for a Tri and measure what my seat post length would need to be at the rails to get the height I need and come up with right about 350mm. So I know I can't go any shorter than 350.

    So, knowing what distance I need from BB to rails, and what angles I want I can then set up a triangle and using the angle and hypotenuse solve for the base, which is the distance back the clamp would need to be from the bottom bracket. I can solve this for all the angles I may want, which I did starting with the measured seat tube angle and then additional angles and came up with...

    73.29D = 239
    74D = 229
    75D = 215
    76D = 201
    77D = 187
    78D = 173
    79D = 158
    80D = 144

    So...if I subtract those numbers from 239 I would get for a 0mm off set, I get the needed offset for any given angle I want.

    74D = 10mm
    75D = 24mm
    76D = 38mm
    77D = 52mm
    78D = 66mm
    79D = 81mm
    80D = 95mm

    Now the last step is to account for saddle adjustment, this is a little more arbitrary as my sit location is not necessarily located at the center of the rails, but I can slide the saddle forward. I currently have it all the way forward which helps some but it ends up putting my sit location only slightly forward of the clamp. But...that being said the rails are about 80mm long, so if your reference point were to be the center of the rails I could in essence pull 40mm from those rails, although I think a number like 20mm is much more realistic. Since this is all relatively fuzzy I have a hard time taking it into consideration when sizing a post because any given saddle will always have adjustment on it and I am concerned with changing the implied frame geometry. Based on some estimations and basic measurements the saddle adjustment seems as though it could potentially get me as much as 2 degrees more upright.

    So, after all of this I can now say with some mathematical certainty that anything shorter than 350mm would not do, and I have to essentially maximize offset with my seatpost choice....or as suggested go custom.

    So my current short list I have found all seem to come up with less than I would like, but there are some options. The longest only seems to give me 25mm, which would only get me to about 75D, but with a little saddle adjustment I may be able to get up around 76-77 and just have to be happy with that.

    Thomson Elite Setback
    31.6 x 367 w/16mm offset

    Bontrager Race X lite ACC
    31.6 x 400 w/20mm offset

    FSA SL-K
    31.6 x 350 w/25mm offset

  11. #11
    Senior Member Barchettaman's Avatar
    Join Date
    Oct 2008
    Location
    Frankfurt, Germany
    My Bikes
    Focus frankenbike trash find commuter, BP Stealth carbon monocoque TT bike, Leader 720 tt, Quantec CC Cyclosross build, Eddy Merckx Corsa Extra Columbus SLX road bike
    Posts
    1,119
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Mate, put away the metric tape measure, plumb bob and the handy dandy calculator and break out the welding gear and an angle grinder.
    Check the thread on cheap tri bikes at the top - one guy made his own seat post.
    Best of luck.

  12. #12
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Barchettaman View Post
    Mate, put away the metric tape measure, plumb bob and the handy dandy calculator and break out the welding gear and an angle grinder.
    Check the thread on cheap tri bikes at the top - one guy made his own seat post.
    Best of luck.
    Oh man, wish I could...really. Sadly not an option for me right now. Closest I can come is paying someone else to make one for me. But yeah, you are totally right would be the best option for me if I was in the situation that I could do that.

  13. #13
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Well, the FSA SL-K definitely doesn't give the saddle angle enough adjustment to run it in a forward position.

  14. #14
    Senior Member jetta-the-hut's Avatar
    Join Date
    Jul 2009
    Posts
    216
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jetta-the-hut View Post
    31.6 mm 367mm setback bend,
    http://www.bikepartsusa.com/bikepart...D&category=316

    31.6 400mm
    http://www.bikepartsusa.com/bikepart...y&category=316

    another option:
    http://www.trisports.com/qurootrish.html

    the only thing I can suggest is getting one of these really long ones and have it bent or welded to the degrees you need. these also have the option on sliding the seat all the way foward to help with the position of your body.

    I'll look some more later but there are a few out there.

    did you look at some of these in the links, they come in 400mm?

  15. #15
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jetta-the-hut View Post
    did you look at some of these in the links, they come in 400mm?
    Yeah I checked those out. The Thomson is an option, but would probably opt for the Bontrager as it has more offset. The quintaroo shuttle looks interesting but would have to buy a specific seatpost for that, so I am not sure about that option yet...it's a possibility. That rockwerx doesn't seem to have an offset.

    I know for sure the Thomson and Bontrager will work for a forward position, the rest I keep trying to find something that says definitively it does. The FSA SL-K implied it did....but once you get your hands on it you can't unless you want a way way leaned back saddle so now I am a little iffy on getting something without seeing it first hand or getting feedback from someone that they have it and it works.

    I know custom is the best bet....but I don't have a welder or access to one. I haven't given up on this option altogether but I just don't know who to go to that I could have one made.

  16. #16
    Senior Member jetta-the-hut's Avatar
    Join Date
    Jul 2009
    Posts
    216
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    i would call them I did on some other stuff I was buying, like a legal helmet for racing. It would take forever to look up all the specs yourself. make them do it, I'm sure they'de be happy to.

  17. #17
    Senior Member Plainsman's Avatar
    Join Date
    Jan 2005
    Posts
    983
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    My Bontrager Race-X-Lite is reversable. I still use it that way even though the bike is now no longer the dedicated tri rig. Not sure if it would give you enough though. Have you talked to anyone at Aerus Composites? I think they are still out of Atlanta, GA. I've tried to find an excuse to buy one of these posts:

    http://aeruscomp.com/index.php?main_...products_id=12

    300mm looks to be the max length they carry in stock, but they may do some custom work. Could be worth a shot, although likely more expensive than having someone weld one for you.
    Life IS an endurance sport. Finish Well.
    Finish Well Endurance

  18. #18
    Member
    Join Date
    Aug 2009
    Location
    NY
    My Bikes
    None yet
    Posts
    42
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    That aerus one looks like a great setup, but too short and a 27.2, looks really nice though. I was definitely looking at the Bontrager as a fall back, with 20mm offset it's not perfect but will get me much closer. I am also looking at the FSA K-force which has 32mm of offset and will be close to ideal....I just don't know if it's reversable. I wish I could get my hands on one even in a shop or if it's the wrong size, really anything...because if I can test the angle it can reach for the saddle then I can just order the right length and diameter.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •