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Seat post questions

rumbatazrumbataz Posts: 796
edited January 2016 in Road beginners
On my old hybrid bike, I asked the shop to cut the seat post and set it very low. I think they cut 2 inches off it (around 5cm).

As it was my first bike I was paranoid about not being able to easily put my feet on the ground whilst seated. I also knew next-to-nothing about cycling at that point.

Several years later I know a bit more and now want to raise the seat height even more. However, I'm a bit concerned about the 2" of seat post that was cut off when I bought the bike.

So, I have a few questions:

1. How much seat post should remain in the seat tube for safety purposes?

2. Should I use any grease when reinserting the seat post into the seat tube?

3. In a worst case scenario, if I wanted to buy a new seat post for my bike (due to not having enough length in the seat post after raising the seat height), would I be able to choose which one I wanted or would I have to buy exactly the same make/model of the seat post that I have already?

4. Would I need a new saddle or would I be able to reuse the existing one?

Posts

  • letap73letap73 Posts: 1,608
    Q1. You should have a minimum insertion mark on the seat post, however, you should probably go above that by the amount the post has been cut by.
    Q2. There should be some grease on the post to ensure that the post does not get stuck - the type of grease maybe governed by the interface material of the post and seat tube. Some poster will come along and hopefully give you a more specific answer to this question.
    Q3. The size of the seat post usually (circular cross section) - 27.2 31.6 etc. Giant have their "aero" seat post which has no other after market solutions.
    Q4. You should be able to use your old saddle.
  • rumbatazrumbataz Posts: 796
    Looks like bad news. I checked the seat post very carefully and it looks like quite a bit had been cut off. I need to raise it by about 3 inches to get it to the right height - yes, that's how low it was - and if I do so, I only have about 2.5 inches of seat post located in the seat tube. I figure this would be quite dangerous.

    Anyway, I checked the diameter using vernier callipers and it appears to be 27.2mm. The height of where it should be and the limiting screw in the seat tube is a little over 360mm.

    Is 27.2mm a standard seat post diameter? Also, what's the nearest standard size to 360mm I ought to get (I imagine I would need less than 360mm)?

    I also noticed there was no grease applied to the seat post so I need to get a tub of basic grease too.

    I found out how to undo the saddle - there's a bolt on the underside of the rail clamp so I can salvage the saddle at least as it appears to be fine. However, I may look to replace that too as it is several years old and I guess I can get a reasonable one for about £20?
  • ForumNewbieForumNewbie Posts: 1,664
    You should get a new seat post to be on the safe side. If your old saddle is comfortable I wouldn't buy a new one. Saddles are a very personal thing and £20, or even a lot more than that, does not guarantee a more comfortable saddle.

    I take it that you're using the old hybrid as a winter bike as you were recently asking about clipless pedals for your road bike. A new seat post and some grease shouldn't cost that much, but worth it for peace of mind.
  • dj58dj58 Posts: 2,193
    Must have been had work riding your hybrid with the saddle setup like that, 27.2 is a standard seatpost size.
  • rumbatazrumbataz Posts: 796
    You should get a new seat post to be on the safe side. If your old saddle is comfortable I wouldn't buy a new one. Saddles are a very personal thing and £20, or even a lot more than that, does not guarantee a more comfortable saddle.

    I take it that you're using the old hybrid as a winter bike as you were recently asking about clipless pedals for your road bike. A new seat post and some grease shouldn't cost that much, but worth it for peace of mind.

    Yeah, hybrid is for Winter use - it's still got it's original steel flat pedals which work fine with my old chunky gym trainers. New road bike has the clipless pedals.

    I'm going to buy a new seat post at the very least as I was a bit shocked at how much had been cut! I imagine a seat post malfunction can be quite painful.
  • rumbatazrumbataz Posts: 796
    Must have been had work riding your hybrid with the saddle setup like that, 27.2 is a standard seatpost size.

    Was it just! I always used to wonder why my hip muscles used to get fatigued very easily. I compared the seat height setup of my road bike against the hybrid (from seat top to crank centre) and there was a difference of at least 3 inches, if not more.

    Because the hybrid was a budget bike I didn't really bother with getting a good 'fit' on it - it was just a case of get on the saddle and start pedalling. The bad seat height was a legacy from years ago when I didn't know where the seat height should be. I never really thought about adjusting it until yesterday!
  • rumbatazrumbataz Posts: 796
    So I bought a Thomson Elite seatpost as it seems to be a highly recommended seatpost on many review sites and cycling sites. I've removed the old seat and loosely attached it to the new seatpost.

    I haven't put it on the bike yet as I want to clean up and relube what needs to be relubed.

    Here's what I plan to do:

    1. Remove the old seatpost clamp and clean it, clean the outside of the seat tube and the inside of the seat tube, and check for any water in the frame (I'm pretty sure it's bone dry);

    2. Put some anti-seize on the seat rail clamp bolts and on the inside of the barrel nut on the clamp;

    3. Grease the very top of the seat tube (where the clamp will fit) and the lower section of the seat post (I'm not exactly sure how far up to lube the seatpost but I guess the lower 2-3 inches should be sufficient as the grease should spread upwards when it's inserted into the seat tube);

    4. Adjust the seatpost height and saddle position before tightening the saddle rail clamp and seatpost clamp to the correct torque. Go for a ride and correct as necessary.

    Is there anything I've missed? I know it's probably a really simple thing to do for most people on here but I want to do things properly.
  • So I bought a Thomson Elite seatpost as it seems to be a highly recommended seatpost on many review sites and cycling sites. I've removed the old seat and loosely attached it to the new seatpost.

    I haven't put it on the bike yet as I want to clean up and relube what needs to be relubed.

    Here's what I plan to do:

    1. Remove the old seatpost clamp and clean it, clean the outside of the seat tube and the inside of the seat tube, and check for any water in the frame (I'm pretty sure it's bone dry);

    2. Put some anti-seize on the seat rail clamp bolts and on the inside of the barrel nut on the clamp;

    3. Grease the very top of the seat tube (where the clamp will fit) and the lower section of the seat post (I'm not exactly sure how far up to lube the seatpost but I guess the lower 2-3 inches should be sufficient as the grease should spread upwards when it's inserted into the seat tube);

    4. Adjust the seatpost height and saddle position before tightening the saddle rail clamp and seatpost clamp to the correct torque. Go for a ride and correct as necessary.

    Is there anything I've missed? I know it's probably a really simple thing to do for most people on here but I want to do things properly.

    Sounds like you know what you're doing!

    Expect to keep adjusting for the first few days, carry around the correct allen keys and only adjust by a few mm's at a time.

    Good luck!
    BikeRadar Communities Manager
  • fenixfenix Posts: 5,437
    Put a wrap of tape around the post just above the clamp - that way if it moves - you'll know easily.
  • rumbatazrumbataz Posts: 796
    Cheers, everyone - seat post replaced with a Thomson Elite seat post and seat adjusted. Did break a new seat post clamp in the process but had the old one to hand which works fine.

    I compared the length of the new seat post and the old one and the old one had almost 3.5 inches cut off it!
  • mfinmfin Posts: 6,726
    How did you break the clamp!?
  • fenixfenix Posts: 5,437
    Silly question - but why did you have the seat post cut anyway ? I've never felt the need on any of my bikes.
  • Silly question - but why did you have the seat post cut anyway ? I've never felt the need on any of my bikes.

    a free way to save weight
  • fenixfenix Posts: 5,437
    When your main concern is being able to touch the ground with both feet - your pedalling style is hampering efficiency so much that a few gr worth of seatpost is worth nothing at all.
  • rumbatazrumbataz Posts: 796
    Silly question - but why did you have the seat post cut anyway ? I've never felt the need on any of my bikes.

    Not a silly question at all. I was in Halfords and I hadn't ridden a bike for several decades. They had a smaller-framed hybrid on sale with a 50% discount which appealed to me as my first bike. As I hadn't ridden a bike for so long I figured that being able to rest my feet on the ground whilst seated was the safe thing to do.

    To be fair the assistant in the shop, he did advise me correctly on the seat height but I told him to cut the seat post so that it could go lower (there's a stop screw in the frame to stop the seat post sinking too low). He cut just over three inches off and I've basically ridden that bike for four years with the seat height around 3-3.5 inches too low. At that point I knew nothing about cycling other than pedalling to go forwards.

    It was only when I got my new road bike a couple of months ago, and after reading these forums, that I realised roughly what the correct seat height ought to be.

    So, having got used to my road bike at the correct height, I turned my attention to the my old bike which would serve me as my Winter bike. I wanted to get it all ship shape so checking the seat height was on my To-Do list. It was at that point I remembered that I had a shortened seatpost.

    I need to raise it be a few inches and there simply wasn't left in the seat tube to be safe, so I ordered a new one as I figure I can get a few more years out of the old bike.
  • Hi,

    Does anyone know if all seatposts with suspension on them can be adjusted for most weights of the average riders?
    For example 60-100kg?
    Is there a way to know how much can seatpost be adjusted for weight?
    :?:
  • dj58dj58 Posts: 2,193
    hector11 wrote:
    Hi,

    Does anyone know if all seatposts with suspension on them can be adjusted for most weights of the average riders?
    For example 60-100kg?
    Is there a way to know how much can seatpost be adjusted for weight?
    :?:

    You would be better starting a new (pardon the pun), post on this subject in the MTB/Commuting forums as I doubt many road cyclist on here use a suspension seat post.

    Suspension seat post can be tuned to rider weight using different rate springs and/or elastomer dampers, there will be a maximum weight limit though. Each manufacturer will use their own design/system so you would need to do some research.

    http://www.rosebikes.co.uk/article/moun ... wgodWeAGHw
  • Thanks for the advice DJ58
    Will try that way.
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