Seatpost diameter

Discussion in 'Bicycle Mechanics and Repairs' started by Rusty Nails, 2 Jan 2019.

  1. Rusty Nails

    Rusty Nails We remember

    Here and there
    Why cannot seatpost manufacturers engrave the seatpost size somewhere at the top of the post rather than at the bottom, where, on an alloy post, it is very likely to get made unreadable after removing and adjusting it many times over the years?

    Not a major problem, I know, but an annoying little detail that would simplify buying a new post if you don't have accurate measuring tools.
  2. You don't know all your seat post sizes off by heart? Call yourself a cyclist? Jeesh.
  3. Ajax Bay

    Ajax Bay Veteran

    East Devon
    I agree it can be a pain - I assume that the aesthetic penalty of a marking where it can be seen is 'not acceptable' to the makers/sellers, and probably to most cyclists too. But your case is slightly flawed: when buying a new post the size marking will be pristine and not worn off, and surely every rider worth their salt knows the diameter of the seat post of each of their bikes. If a rider has so many bikes and is not prepared to document the sizes, then ownership of calipers is a requirement where N>3.
  4. Wrap yer mum's dressmaking tape measure around it and divide by pi?

    Hold on. The only valid seat post size is 27.2 so if 27.2 doesn't fit you need to throw the bike away and start again.
    tyred, C R, mikeymustard and 7 others like this.
  5. OP
    Rusty Nails

    Rusty Nails We remember

    Here and there
    Many people like to buy old bikes, and some, whisper it quietly, like to have many of them.

    The aesthetic penalty does not really exist as there are many easily accessible places to put three small digits which cannot be easily seen unless you want to.
  6. southcoast

    southcoast Senior Member

    Measure the post with a vernier, always good to have one in the toolbox. A very useful tool to have.
    Smokin Joe and Heltor Chasca like this.
  7. Ajax Bay

    Ajax Bay Veteran

    East Devon
  8. OP
    Rusty Nails

    Rusty Nails We remember

    Here and there
    At my age I can hardly remember the names of my kids, never mind bloody seatpost sizes!

    I bought a rear wheel a couple of weeks ago for a bike I'm building, and only after I'd bought it did I find I had one the right size and cassette in the pile of spare wheels in the shed.

    I think I am a cyclist, but I know I'm not a proper cyclist.
    SpokeyDokey, C R, mickle and 3 others like this.
  9. meta lon

    meta lon Guru

    Try getting a seat post from Ann'll know the exact size !!!

    But I agree27.2 , 30, 30.9 and 31.6?? Why not have just one size or at the most 2 for the road and MTB.
    Illaveago likes this.
  10. Afnug

    Afnug I'll Sithee

    A few missing there.

    raleighnut, Threevok and Illaveago like this.
  11. meta lon

    meta lon Guru

    It's a Joke really..
    I think I have about 7-8 posts in my stores.
    I'm sure I'll use them..maybe:smile:

    I do have some seat post shims,there handy with dropper post fitting,as long as your sizing up
    Last edited: 3 Jan 2019
    Afnug likes this.
  12. Heltor Chasca

    Heltor Chasca Out-Riding the Black Dog

    In the olden days they were very expensive. Now, even a tramp like me can afford one from Screwfix. I brought one home a couple of years ago and showed it off to my 80 year old engineer neighbour. He held it like the Magna Carta and purred gently. Quietly hinting I wasn’t worthy and should stick to the ‘Poor Man’s Adjustable Spanner method’.

    Then I told him the price. (Less than £20) I think he thinks I nicked it.
    SpokeyDokey, southcoast and Threevok like this.
  13. Yellow Saddle

    Yellow Saddle Veteran

    Loch side.
    Because of progress. We went from thick-walled pipe, to drawn CroMo tubing, to oversize aluminium, to odd-shaped carbon, with a detour via Russian-supplied titanium tubing to get where we are today. Count your lucky stars that there are only a few standards. You'll find that on modern bikes it is we play around with just three sizes, if we exclude silly proprietary triangular and oval shapes like that found on TT bikes.
    meta lon likes this.
  14. roubaixtuesday

    roubaixtuesday Senior Member

    SpokeyDokey, Milkfloat and mickle like this.
  15. rogerzilla

    rogerzilla Guru

    Thomson engrave them where they can be read, I think.
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