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Seat post diameter questions and suggestions

dima_moteldima_motel Posts: 26
edited April 2017 in Workshop
Hello,

I'm looking to buy a new carbon seat post.
Like with everything related to cycling, there are too many options.
So far, I've settled on Easton EC70 Zero Carbon Seat Post.
I'd appreciate other suggestions as well.

First I'd like to know what's the difference between offset and zero? I'm 1.62 (if that makes any difference).
Second, I'd like to know how to choose the Diameter / Length part - I have no idea what's my seat post diameter (there's no info online at all - I have a De Rosa King XS). The length is between 300-400 mm, I'm guessing that it relates to once height, so I'm supposed to get 300mm.

Your answers would be very much appreciated.
Thank you,

Posts

  • keezxkeezx Posts: 1,318
    1-Zero offset is center saddleclamp is in centerline seat post.
    2-Measure frame seatpost hole.

    Done.
  • arlowoodarlowood Posts: 2,531
    Dima_Motel wrote:
    Hello,

    I'm looking to buy a new carbon seat post.
    Like with everything related to cycling, there are too many options.
    So far, I've settled on Easton EC70 Zero Carbon Seat Post.
    I'd appreciate other suggestions as well.

    First I'd like to know what's the difference between offset and zero? I'm 1.62 (if that makes any difference).
    Second, I'd like to know how to choose the Diameter / Length part - I have no idea what's my seat post diameter (there's no info online at all - I have a De Rosa King XS). The length is between 300-400 mm, I'm guessing that it relates to once height, so I'm supposed to get 300mm.

    Your answers would be very much appreciated.
    Thank you,

    A bit of searching suggests that your De Rosa King XS has a requirement for a 31.6mm diameter seat post so you should be using that as your first search criteria.

    http://www.wrenchscience.com/road/frame ... g+XS/2017/

    Secondly, at your height you will probably be on a small to medium frame so a length of 300mm will probably be fine. Unless of course you have odd body proportions (long legs/short torso) meaning that you have to run with a lot of seat post showing to get a correct fit.

    Regarding offset - this refers to the centre of the saddle clamp in relation to the centre line of the seat post/seat tube. With an offset seat post the centre of the saddle clamp can be say 12 - 25mm offset to the rear. See image below
    easton-ec70-carbon-offset-post.jpg?w=430&h=430&a=7

    With zero offset or inline seat posts the centre of the saddle clamp is in line with the centre of the seat post/ seat tube. See image below

    easton-ec70-carbon-post.jpg?w=430&h=430&a=7

    Whether you have an inline (zero) or offset seat post depends what your bike set up demands to get an ideal riding position
  • Could not thank you enough arlowood.
    Thank you for the detailed explanation.

    Regards,
  • BobbinogsBobbinogs Posts: 4,841
    If you are unsure about seatpost length then the trick is to measure your current seatpost (assuming you have one) in terms of what is sticking out of the frame. Then check with the new post to ensure that it can be inserted to the min depth and have the right amount for you above the frame. Most posts will quote the min insertion or have it marked on them. Don't try and stick it in and see, as it is pretty much impossible not to score a carbon post and no one will accept one back on the grounds of "I haven't actually used it, just tried it". You should be able to get a very good idea though just lining it up next to the frame so if you have got the wrong sized length then it can go back (with the usual caveats about saleable condition, including packaging).

    The problem is that all frames have slightly different geo and everyone has their own seatpost height set so it is not possible for anyone to specifically advise in isolation but just go along the lines as above, as in it should be ok.

    Don't forget to use carbon paste as that should stop it slipping and avoid you over-torqing it. Oh, and don't forget to take it out (after marking the setting), wiping it down, re-pasting and reassembling every 6 months. This will stop it seizing (note to self, don't leave it in for a couple of winters only to find that the bloody thing is set for good!).
  • ugo.santaluciaugo.santalucia Posts: 26,492
    Is there anything wrong with your seatpost? Seatpost/stem upgrades are generally a pointless waste of money, unless your current one is not working properly
  • timothywtimothyw Posts: 2,482
    Is there anything wrong with your seatpost? Seatpost/stem upgrades are generally a pointless waste of money, unless your current one is not working properly

    I agree about stems, but seatposts you can usually save a reasonable amount of weight for not outrageous amounts of money if you shop around, and with a bit of luck improve comfort also.

    Plus, y'know, if you prefer the way the bike looks with a new post then that might be worth it in itself....
  • ugo.santaluciaugo.santalucia Posts: 26,492
    TimothyW wrote:
    Is there anything wrong with your seatpost? Seatpost/stem upgrades are generally a pointless waste of money, unless your current one is not working properly

    I agree about stems, but seatposts you can usually save a reasonable amount of weight for not outrageous amounts of money if you shop around, and with a bit of luck improve comfort also.

    Plus, y'know, if you prefer the way the bike looks with a new post then that might be worth it in itself....

    They all weigh around 200 grams... some a bit more, some a bit less... they also are pretty much all black, so even there, not much difference
  • timothywtimothyw Posts: 2,482
    I've come across plenty of seatposts (as in, the cheap type that come with new bikes) that weigh in the 350g ballpark.

    There are generally better places to spend the money, sure, but it's a much better result than carbon bottle cages...
  • fenixfenix Posts: 5,437
    Your current seatpost will be stamped with the diameter.
  • The RookieThe Rookie Posts: 27,748
    I've seen stock seatposts over 400g (Merida built generic design single bolt in 31.6mm) but I doubt a De Rosa King will have one weighing much over 250g
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