Minimum insertion

[FastforaSlowGuy]

Just got a new to me seat post and its a bit shorter than I expected. Anyone know how much is the minimum insertion for a carbon post? No markings on it.

[echelon_john]

Best Thread Title Ever.

Great band name, too.

[markie]

I think minimum insertion has more to do with the frame. I want the seat post to finish well below the bottom of the top-tube. Normally at least the diameter of the top tube below the bottom of the top tube. How short is it?

[ultraman6970]

I read time ago something about 2 inches or so.So you bought a seatpost that was cut??? Never understood the brainiaks that cut seatposts because are too long expecting to save 10 grams...

A guy in my local CL is selling a Thomson seatpost for 60 bucks and was actually cut in a half.

[FastforaSlowGuy]

It looks awfully well finished to be cut. I think it's just short.

[Don49]

What's the actual length and the brand?

[witcombusa]

Thought this was about something else...

[hockeybike]

More than just the tip.

Sorry.

Well, not really. haha

Edit: There was a thread about this post issue a while ago--I think the consensus from some framebuilders was at least cm or two below the bottom of the top tube.

[DRietz]

Minimum insertion matters for the post because it might have a chance of snapping if not well enough buttressed within the frame. Typically, they're so overbuilt that the whole breaking aspect isn't a big deal, but the "damaging your frame aspect" is.

To be safe for your frame, it's typically advisable to have two inches of post under the TT/ST junction.

[thirdgenbird]

I read time ago something about 2 inches or so.So you bought a seatpost that was cut??? Never understood the brainiaks that cut seatposts because are too long expecting to save 10 grams...

A guy in my local CL is selling a Thomson seatpost for 60 bucks and was actually cut in a half.

I did run into a situation where a Thomson hit the water bottle boss on a tiny frame. Seat tube cut outs or crimping can cause the same constraint. Other than those situations I don't think I would bother.

[FastforaSlowGuy]

In that case, I'm golden!

More than just the tip.

Sorry.

Well, not really. haha

Edit: There was a thread about this post issue a while ago--I think the consensus from some framebuilders was at least cm or two below the bottom of the top tube.

[BumbleBeeDave]

It looks awfully well finished to be cut. I think it's just short.

. . . what SHE said!

HaHa!!! Said it first, said it first! Na-Na-Nuh-Na-Na!! :p

BBD

[Peter P.]

Use markie's rule.

The bottom of the post HAS to be below the top tube otherwise it leverages the welded joints in the area too much.

[ultraman6970]

You are correct but you actually have to see the one being sold in CL hehe probablyu the frame was for a little kit maybe a 37 frame size and built with oversize tubing heheh because the darn seatpost is like 10 cm in length :D

I did run into a situation where a Thomson hit the water bottle boss on a tiny frame. Seat tube cut outs or crimping can cause the same constraint. Other than those situations I don't think I would bother.

[pdmtong]

agreed withthe comments about burying below the TT...that said, the in insertion on the easton carbon posts I have is 3".

I suspect the ritchy, alpha Q and specialized carbon posts I have would be similar.

reminds me of an old joke...

girl looks a guy and dismissively says " who do you expect to please with that"

guy says

"


[wait for it]





.................me"

[cash05458]

put it far enough in just to the point it becomes uncomfortable then back it out about 2 mm...

[oldpotatoe]

Just got a new to me seat post and its a bit shorter than I expected. Anyone know how much is the minimum insertion for a carbon post? No markings on it.

General rule of thumb-bottom of the seatpost twice the width of the top tube, below the bottom of the top tube. So..if the top tube is 2cm width, the bottom of the seatpost 'should' be 4cm below the bottom of the top tube.

[ultraman6970]

When i read minimal insertion the 1st time I thought it was a thread about the biggest lies ever.

1 Don't worry honey, i swear it will be just the tip!

2 I swear it wont hurt!

3 Remind me tomorow to give you the money back.

[jtakeda]

Semi thread drift here...

Whats the minimum insertion for an alloy post on a steel frame?

Same rules apply?

[cash05458]

can't speak for Peter via the above post...but I have always gone by that rule he gives above for any sorta post or frame whatever the material...never had a problem...

[jtakeda]

Looking at that rule of thumb, old campy aero posts, which are typically very short would have to be slammed in the frame.

That's why I ask, dealin with a slightly small frame and a campy aero post.

[cash05458]

Looking at that rule of thumb, old campy aero posts, which are typically very short would have to be slammed in the frame.

That's why I ask, dealin with a slightly small frame and a campy aero post.

as long as you get past the taper or rather, keep that taper just above the seatpost tube line then I am pretty sure it is ok...I have been riding one of those for nearly two decades...

[Hawker]

. . . what SHE said!

HaHa!!! Said it first, said it first! Na-Na-Nuh-Na-Na!! :p

BBD

Channeling Michael Scott here. :)

[oldpotatoe]

Semi thread drift here...

Whats the minimum insertion for an alloy post on a steel frame?

Same rules apply?

Yep, you aren't just protecting the seat post but mostly the frame.

[godfrey1112000]

Best Thread Title Ever.

Great band name, too.


The thought of it makes me feel a little uneasy:eek: