Seat Post Question

[twentysix by twentyfive]

Just how much seat post should be in the seat tube for safety reasons please?

I have about 1.5 inches in on this new frame and this feels in my guts to be too little.

 

[PpPete]

"I have about 1.5" in......"

All sorts of facetious & disgusting responses come to mind....

But there should be a "minimum insertion" mark on the seat post.

 

[RecordAceFromNew]

The problem is sometimes long seatposts are sawn to save weight, so the minimum insertion mark even if left becomes meaningless. For what it is worth, I have yet to see a minimum insertion mark for an uncut post that is less than 3 or 4 inches.

 

[twentysix by twentyfive]

Ah yes - found it, there is a mark about 3 inches from the bottom (and not sawn off either). It was well hidden amongst scratches and lots of grease

So I need a new post.

Thanks all

 

[Crankarm]

The more you have in the hole the better. I wouldn't want to save weight in this area as the consequences can be serious. So max length and max insertion with a nice tight clamp around the head of the tube. You need a good lubricant/anti seize paste as well .

 

[Landslide]

Regardless of the manufacturer's minimum insertion mark, you should always have enough in the frame that it extends below the toptube (particularly important if you've got a frame with an extended seattube).
Personally, my rule of thumb is at least a third of the seatpost should be within the frame (e.g. 300mm seatpost length = 100mm insertion).

 

[twentysix by twentyfive]

I've now got a new seat post and about 50% is inserted. I won't be chopping anything off either.

The only time I've ever sawn off a seat post was when it went so far down into the seat tube it was fouling on the bottle bosses and was still too high for me. It was quite a long post.