Exposed Seat Post Length

[PaulSB]

No, this isn't an "an asking for a friend" post!

Someone I ride with, a tall, heavy, big man rides with a lot of seat post exposed. I'm guessing at 9 - 12". His seated position is such that his hips rock from side to side and the seat post visibly flexes with every stroke. I'm not the only person to have noticed this, good friends have commented to me.

In my view, subjective I know, rocking hips indicates poor bike setup. What genuinely concerns me is the seat post flexing. Would repeated flexing, on every pedal stroke, eventually weaken the post and cause it to snap? If it is a danger I'm beginning to think I should say something - which would be very difficult.

Possibly the frame is too small for the individual?

 

[ColinJ]

That really does sound like the saddle is way too high!

If he lowered his saddle to stop the hip rocking then that should sort out the post flexing issue too.

The potential problem is communicating your feelings to the rider in question...

I cycled up behind someone with a very similar bike setup once and made the mistake of offering unsolicited advice. The rider flew into a rage and unleashed a torrent of abuse on me!!

So, my advice would be to ask the rider first if he would like to hear your comments on his setup! Yes: Speak up. No: Leave him to it.

 

[classic33]

Where it's clamped by the frame will be acting as a pivot point, more likely to fail than the seat post.

 

[si_c]

I had an alloy Felt VR which had about 300mm of exposed seat post (see photo), used it for just over 2 years before the weld failed at the seat tube/top tube join. At the time I put it down to excessive leverage from the seatpost - there was plenty of post in the frame incidentally - and nothing has dissuaded me of that opinion since.

The bike was the correct size for me reach wise but the modern geometry meant that the seat post did need to be longer than was probably wise - I had to get a 400mm post to replace the original 330mm one. The replacement bike was a Kinesis in a 63cm frame size which didn't have this issue.

 

[N0bodyOfTheGoat]

Rocking hips sounds like saddle too high, I always thought at least 10cm of seat post should be inserted into seat tube, possibly more if it doesn't get below top tube junction.

 

[wafter]

I had an alloy Felt VR which had about 300mm of exposed seat post (see photo), used it for just over 2 years before the weld failed at the seat tube/top tube join. At the time I put it down to excessive leverage from the seatpost - there was plenty of post in the frame incidentally - and nothing has dissuaded me of that opinion since.

The bike was the correct size for me reach wise but the modern geometry meant that the seat post did need to be longer than was probably wise - I had to get a 400mm post to replace the original 330mm one. The replacement bike was a Kinesis in a 63cm frame size which didn't have this issue.

View attachment 774560

+1 for such a failure on an ally frame.. would certainly expect this to fail before the seatpost given the lever arms and material thicknesses of both parts, as well as the presence of welds on the frame.

 

[PaulSB]

I had an alloy Felt VR which had about 300mm of exposed seat post (see photo), used it for just over 2 years before the weld failed at the seat tube/top tube join. At the time I put it down to excessive leverage from the seatpost - there was plenty of post in the frame incidentally - and nothing has dissuaded me of that opinion since.

The bike was the correct size for me reach wise but the modern geometry meant that the seat post did need to be longer than was probably wise - I had to get a 400mm post to replace the original 330mm one. The replacement bike was a Kinesis in a 63cm frame size which didn't have this issue.

View attachment 774560

This image is very similar to the one I'm concerned by. I'm not being critical but to me it looks crazy but then I'm 5'6" and 29" inside leg. I find it hard to imagine how a rider can be comfortable on this setup.

One small problem I have is being able to use seatpost mounted gear. For example on one bike I can't run a saddlebag and Varia.

One of my regular cycling buddies is much more diplomatic than me. We've discussed the issue. I think we should discuss our approach next.

 

[biggs682]

Why not get him to try a larger frame and show them the difference.
Be careful as some people don't like being advised anything, but certainly sounds like they need to buy the next size up .

 

[raleighnut]

Maz bought me a Saracen Blitz (don't ask) bike many years ago, it's a 'Jump' bike so the saddle was never high enough so I had a custom 600mm seatpost made. I've had no end of people comment that I've got too much seatpost out but it won't go any further into the frame.
Bike was used as a snow commuter (discs front and rear)

 

[Pduk]

Depending on the length of rides you're going on, the chaps hips rocking while pedaling could be causing him some discomfort and even lower back pain after a while, if he ever mentions that, it could be a good opener to suggest looking into how his bike is set up and / or a larger framed bike maybe a worth while investment.
You may find he's open to suggestions, I know if I was doing something that could be improved, I'd happily take on advice from other riders.

 

[ianrauk]

Agree with others. Some people don't take kindly to being 'advised' that their set up 'may' be wrong. A gentle approach may be needed.

 

[fossyant]

Maybe check the length of the inserted seatpost, say you can see it flex and are worried there isn't enough in there - it needs to be way past the seat stays. It's a reason I'm not too keen on some current frame designs as it's inducing flex where you really don't want it.

 

[si_c]

This image is very similar to the one I'm concerned by. I'm not being critical but to me it looks crazy but then I'm 5'6" and 29" inside leg. I find it hard to imagine how a rider can be comfortable on this setup.

I'm around 6'5" and that Felt is a 61cm frame - the largest available usually. For comparison I've added my Kinesis RTD which is a 63cm frame which has a good few inches of seatpost exposed still but much less due to the level top tube, the position overall is very similar.

One small problem I have is being able to use seatpost mounted gear. For example on one bike I can't run a saddlebag and Varia.

Not a problem I have usually

Maybe check the length of the inserted seatpost, say you can see it flex and are worried there isn't enough in there - it needs to be way past the seat stays. It's a reason I'm not too keen on some current frame designs as it's inducing flex where you really don't want it.

Yeah that's a concern I have, but the trade off is that the extra flex does make the bikes more comfortable to ride. My Felt was definitely one of the more comfortable bikes I've had in terms of ride, comparable to my Domane which has the decoupler at the rear.

 

[presta]

I'm 6'5", and this is plenty enough seatpin for me:

 

[fossyant]

Modern bikes do have more compact frames, so more seatpost shows. Just make sure you've got a fair amount inside the seat tube and are nowhere near the limit.