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-   -   Maximum seat height (https://www.bikeforums.net/general-cycling-discussion/1253062-maximum-seat-height.html)

himespau 06-07-22 09:35 AM

Take the post out and learn to ride standing. It's the only way that makes sense for you with this frame.

genejockey 06-07-22 09:35 AM

You know, if you're gonna do it anyway, why even ask people who know much better than you whether you should do something?

genejockey 06-07-22 09:36 AM


Originally Posted by livedarklions (Post 22533642)
I vote you keep the seat post and replace the frame with a larger one.

I know a guy who bought an entire bike for a seatpost. It was a very nice seatpost, and he ended up restoring the whole bike. But still.

livedarklions 06-07-22 09:43 AM


Originally Posted by genejockey (Post 22533662)
I know a guy who bought an entire bike for a seatpost. It was a very nice seatpost, and he ended up restoring the whole bike. But still.


Freud would have fun with that story.

genejockey 06-07-22 09:46 AM


Originally Posted by livedarklions (Post 22533672)
Freud would have fun with that story.

"Sometimes a seatpost is just a seatpost."

genejockey 06-07-22 09:49 AM


Originally Posted by base2 (Post 22533316)
It's not necessarily the height of the seat post (thought that is a big part of the lever) as much as it is the amount of post inside the frame to counter (be equal & opposite) the forces of you sitting on the post levering it around.

A foot between the saddle & seatpost clamp with 4 inches of post in the frame equals a 3:1 multiplication. Ergo 200 pounds of you equals 600 pounds trying to blow apart the seattube/top tube junction. Mentally multiply to that 2,3,4g transient loads from potholes etc...You'll see we are dealing with appreciably large forces on relatively thin walled tubing. An inch of post inside the frame with a 200 pound you a foot above is 2400 pounds of bending force. Well over a ton...& that's just a static value. A simple unexpected bump could easily make momentarily well over 10,000 pounds or more lever force trying to pry your bike apart.

Don't be stupid. Get a longer post that at least extends down to below the lower top tube weld.

Multiply that 200 by 1.3.

base2 06-07-22 10:12 AM


Originally Posted by genejockey (Post 22533683)
Multiply that 200 by 1.3.

Why?
It's a first-order lever.

The seat-post clamp is the fulcrum. Larry is the effort force (200 pounds @ 12 inches distance.) The bottom of the seat post inside the frame is the load (600 pounds @ 4 inches from the fulcrum).

First-order levers are force multipliers.

You might be thinking a second-order?

livedarklions 06-07-22 10:16 AM


Originally Posted by base2 (Post 22533712)
Why?
It's a first-order lever.

The seat-post clamp is the fulcrum. Larry is the effort force (200 pounds @ 12 inches distance.) The bottom of the seat post inside the frame is the load (600 pounds @ 4 inches from the fulcrum).

First-order levers are force multipliers.

You might be thinking a second-order?


Larry is 260 pounds.

genejockey 06-07-22 10:26 AM


Originally Posted by base2 (Post 22533712)
Why?
It's a first-order lever.

The seat-post clamp is the fulcrum. Larry is the effort force (200 pounds @ 12 inches distance.) The bottom of the seat post inside the frame is the load (600 pounds @ 4 inches from the fulcrum).

First-order levers are force multipliers.

You might be thinking a second-order?

Because he weighs 260, not 200.

genejockey 06-07-22 10:26 AM


Originally Posted by livedarklions (Post 22533715)
Larry is 260 pounds.


Originally Posted by genejockey (Post 22533724)
Because he weighs 260, not 200.

You beat me to it.

livedarklions 06-07-22 10:35 AM


Originally Posted by genejockey (Post 22533726)
You beat me to it.

Cuz I'm a first-order smartass.

ThermionicScott 06-07-22 10:37 AM


Originally Posted by genejockey (Post 22533658)
You know, if you're gonna do it anyway, why even ask people who know much better than you whether you should do something?

Did you forget who the OP is? :D

genejockey 06-07-22 10:42 AM


Originally Posted by livedarklions (Post 22533737)
Cuz I'm a first-order smartass.

That, and I was in a meeting.

base2 06-07-22 10:44 AM


Originally Posted by genejockey (Post 22533724)
Because he weighs 260, not 200.


Originally Posted by livedarklions (Post 22533715)
Larry is 260 pounds.

Ha!
Ok, you both are right!

While diligently working on my BFEngineering degree, I was turning the result in my head of running it as a second order to find the tension the seat/top tube junction was under & not just the load at the bottom of the seat post...I came back to say you may have been on to something. I see you were right about that, too! :rolleyes:

Ok. It's time I realize my BFEngineer license is due to be revoked. Where do I turn it in at? :roflmao:

Steel Charlie 06-07-22 10:47 AM

I've seen a lot of bad ideas suggested on these forums but welding an extension on an alloy seatpost has to be right at the top. I mean we're talking pennies on CL for a proper one.

seypat 06-07-22 10:50 AM

I think if you are going to talk about maximum seat height, you need to discuss max headroom as well. Very important to this thread.


phughes 06-07-22 10:51 AM


Originally Posted by LarrySellerz (Post 22533281)
Honestly the seatpost isn't that high

Yes it is.

himespau 06-07-22 10:53 AM


Originally Posted by Steel Charlie (Post 22533747)
I've seen a lot of bad ideas suggested on these forums but welding an extension on an alloy seatpost has to be right at the top. I mean we're talking pennies on CL for a proper one.

We keep saying that a proper seatpost is available. However, OP claims he should be riding a 63 cm frame but is on a 47 cm frame. A 350 or 400 mm seatpost might not be big enough. There might not truly be a long enough seatpost available. That doesn't solve the problem that he should be riding a frame that fits though.

phughes 06-07-22 10:56 AM


Originally Posted by livedarklions (Post 22533737)
Cuz I'm a first-order smartass.

Better a smart ass than a dumb ass I always say.

seypat 06-07-22 10:59 AM

I'd be be worried about all of that weight out over the front wheel/axle. That bike might handle like crap, especially when climbing. OP probably thinks he has a brake dragging or a flat tire when going uphill. Come to think about it, didn't he have a thread about his disc rotors rubbing? I can see why.

LarrySellerz 06-07-22 11:13 AM


Originally Posted by seypat (Post 22533760)
I'd be be worried about all of that weight out over the front wheel/axle. That bike might handle like crap.

Yeah its kind of terrible to handle, but im getting used to it. It was suggested to me to get a longer stem which should make it less twitchy

livedarklions 06-07-22 11:18 AM


Originally Posted by phughes (Post 22533759)
Better a smart ass than a dumb ass I always say.


Alas, one can be both.

seypat 06-07-22 11:22 AM


Originally Posted by seypat (Post 22533760)
I'd be be worried about all of that weight out over the front wheel/axle. That bike might handle like crap, especially when climbing. OP probably thinks he has a brake dragging or a flat tire when going uphill. Come to think about it, didn't he have a thread about his disc rotors rubbing? I can see why.

Same thing going downhill. Think about how much weight is on the front of the bike and how the rear could get loose. Getting into dangerous territory.

79pmooney 06-07-22 11:27 AM


Originally Posted by Steel Charlie (Post 22533747)
I've seen a lot of bad ideas suggested on these forums but welding an extension on an alloy seatpost has to be right at the top. I mean we're talking pennies on CL for a proper one.

It's a great idea. It gives the user a chance to see firsthand failure modes in compromised alloys subjected to cantilever bending. (But he really should spend his time riding looking between his legs to be sure he doesn't miss the key moment. And with the money he saves on a new post, he can invest in a bridge I'm proposing. Based on the breakthrough Tacoma Narrows design.)

J.Higgins 06-07-22 12:14 PM


Originally Posted by livedarklions (Post 22533781)
Alas, one can be both.

Also, let's not forget that there is a distinct difference between something being "dope", and something being "dopey".


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