minimum seatpost insertion

crispy1980
crispy1980 Posts: 310
edited March 2014 in MTB workshop & tech
Just a quick one, is the,amount of minimum insertion relative to the total seatpost lenght or is it frame specific?

Comments

  • 02gf74
    02gf74 Posts: 1,171
    generally posts are marked at 100 mm but I have had 1 post with 90 mm insertion.
  • stubs
    stubs Posts: 5,001
    A good rule of thumb is make sure the bottom of the post is at least 1 inch (25mm) below the bottom of the toptube weld. Its not perfect and I always prefer a bit more but its a start.
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  • crispy1980
    crispy1980 Posts: 310
    Reason I ask is I have two spesh xc bikes, one US the older,through frame shock. They both are large but the newer bike has a longer seatpost and,minimum insertion is marked at 100mm. The other is shorter and minimum insertion is shorter, but don't know if this has,been cut down before.
  • stubs
    stubs Posts: 5,001
    I have never come across a post marked with less than 100mm of insertion, if you think its been cut then get the ruler out and mark at the absolute minimum 90mm. Spesh fames with the through shock and very short seatpost tubes are a problem my mate has one and we cut the post in 10mm increments till we found a length that left enough post in the frame but allowed him to drop it for techy bits.
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  • nicklouse
    nicklouse Posts: 50,675
    Seat post insertion is marked on the post. Some frames also state a minimum insertion depth.

    If a frame says 100 and the seat post says 90 which would you use?

    I would use the figure the frame states.
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  • Cqc
    Cqc Posts: 951
    stubs wrote:
    I have never come across a post marked with less than 100mm of insertion, if you think its been cut then get the ruler out and mark at the absolute minimum 90mm. Spesh fames with the through shock and very short seatpost tubes are a problem my mate has one and we cut the post in 10mm increments till we found a length that left enough post in the frame but allowed him to drop it for techy bits.
    Yeah I've got that type of bike, tbh I have very little post in there (under 8cm) and it's fine
  • cooldad
    cooldad Posts: 32,599
    Everything is fine until it breaks.
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  • njee20
    njee20 Posts: 9,613
    Spesh frames have a little hole on the seat tube, the post needs to cover this.
  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    nicklouse wrote:
    Seat post insertion is marked on the post. Some frames also state a minimum insertion depth.

    If a frame says 100 and the seat post says 90 which would you use?

    I would use the figure the frame states.

    Surely the sensible thing to do would be to stick to the greater of the two figures.
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  • Cqc
    Cqc Posts: 951
    njee20 wrote:
    Spesh frames have a little hole on the seat tube, the post needs to cover this.
    exactly, and the hole is about 3.5 cm down, so its fine
  • Chunkers1980
    Chunkers1980 Posts: 8,035
    If you think so then fill your boots. I'd like more.
  • njee20
    njee20 Posts: 9,613
    Mmmm, I wasn't suggesting that to cover that hole is entirely sufficient, just that it's there!

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