How much seat post do i need in my tube?

[chef7734]

So i am wondering how much seat post needs to be in my tube on my 2011 giant reign? I think the shop owner cut off too much.

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[mitzikatzi]

4 inches is a good starting point.
Try to have 1 inch of seat tube below the junction of the seat and top tube (bottom side of tube).

[chef7734]

Thanks. That gives me about 6" left on top. Hopefully that is enough. I will check tomorrow.

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[nauc]

check your post, a lot of posts have a minimum insertion line

[chef7734]

How is that accurate if they took of some of the tube. The min insertion line is only about an inch from the cut on the tube.

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[chef7734]

He cut my seat post to about 10 inches. Take 4" which puts it on the 65mm mark leaves me with 6" above the tube.

[saturnine]

just the tip, it's the most sensitive part.

[uncle mama]

He cut my seat post to about 10 inches. Take 4" which puts it on the 65mm mark leaves me with 6" above the tube.

I would find a new LBS. They ruined your seatpost.

[chef7734]

Yeah I am looking for a new one. Not many around here. Had to drive about an hour to go to that one. I will start looking for seat posts. Eventually will get a dropper post.

[uncle mama]

Yeah I am looking for a new one. Not many around here. Had to drive about an hour to go to that one. I will start looking for seat posts. Eventually will get a dropper post.

Allow me to correct myself You can use your post safely by finding out what the minimum insertion is on a new post, of the same make and model. Just make sure you insert the minimum. Your post will possibly be too low on the climbs but, that sure beats breaking your post, crashing, getting hurt...

[The R]

I don't know if all bikes have this, but Specialized puts a small hole on the rear-facing side of the seat tube. If your bike has one, you should be able to see the seat post through the hole. If you can't, it's not in there deep enough.

[Blind]

the owners manual for my santa cruz specifies to ignore seatpost markings and to always keep a minimum of 100mm of seatpost in the frame. I think that should be pretty universally safe.

[nauc]

How is that accurate if they took of some of the tube. The min insertion line is only about an inch from the cut on the tube.

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my bad, i didnt see that its been cut

[One Pivot]

The minimum insertion line on all my posts sketches me out. I wouldnt want to run at the minimum, a couple inches past that makes me more comfortable.

[Fuglio]

Lets back up SF....... why did they cut it????

[chef7734]

Lets back up SF....... why did they cut it????

When i took the bike in to be built.

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[Fuglio]

Giant Reign 2010 Seat Tube Seat Post

What droppers you looking at? ... id say ride with 4.5" in on your current post and just deal with it till you get a dropper. Looks like the reign wont let you slam the post down all the way and still have enough legnth to pull it out for climbing height. Causevits not a uninterupted seat post on the frame... buying a new post wont fix that and it dont look like the shop owner did you wrong too much.... if you went in and talked to him i bet he would give you a take off post that he has kicking around..

[BXCc]

I don't know if all bikes have this, but Specialized puts a small hole on the rear-facing side of the seat tube. If your bike has one, you should be able to see the seat post through the hole. If you can't, it's not in there deep enough.

Which hole are you talking about? Is it a couple inches down or just at the bottom of the cut? Almost all put a slot so the tube will compress around the seat post. The hole at the bottom of the cut is a relief hole. It relieves stress from the straight cut so it will not continue and form a crack. If that is the hole you are referring to, you will be in a world of hurt if that's the only insertion you have.

[mitzikatzi]

SEATPOST MINIMUM INSERTION:
To prevent damage to the frame, it’s important to have a minimum amount of seatpost in the seat tube.
If you cannot see the seatpost tube through the seat tube hole, your seatpost is too far extended. If a greater saddle height is
required, replace the seatpost with a longer one

from page 6 specialized pdf/manuals

[dv8xin]

I believe there's a min insertion length for a seatpost and a min insertion length for a frame.

The line on the seatpost is for the seatpost, assuming it's uncut. For frames, I think the general guide line is to have the bottom of the post extend at least just below the lower weld of the top tube.

If you're a lightweight, you can get away with a bit. If you're a heavyweight, you better be more conservative and have more post in the frame. If you got a lot of post sticking out, you should try to have a comparable amount in the frame, long levers and all, ya know.

No source to cite. I'd be citing up Sheldon Brown's site if he had such an article, but I think this is supposed to be common bike knowledge.

[BXCc]

from page 6 specialized pdf/manuals

Cool, but to make sure we are all on the same page and some green horn biker doesn't make a painful mistake, this (I hope) is NOT the hole in question. (Sorry for the crap picture)

[thickfog]

You can't just cut a seatpost and say yup ok till the min insertion line.

Frames and seatpost have limits. Frame limits are generally not published or even known.

This can put too much stress on the frame's seat tube and your seatpost with what your bike shop did.

[mitzikatzi]

Cool, but to make sure we are all on the same page and some green horn biker doesn't make a painful mistake, this (I hope) is NOT the hole in question. (Sorry for the crap picture)

That is not he "hole in question"

Really it is not that hard. 4 inches is a good start. Having 1 inch of seat post below the bottom of the top tube is even better.