Mountain Biking - New Seatpost...(sigh)

Ok so i've heard that the seatpost on the GF cobia (bontrager sport) sucks and that it slips and what-not. I also was hoping that it was just some crazy malfunction thats not gonna happen to me but that turned out to be wrong...so anyways im looking for a new seatpost and want something around $40 my LBS has three im looking at and was wondering if they were worth it...

1:Cannondale Fire Carbon 27.2x250mm ($40)
http://wheelandsprocket.com/itemdetails.cfm?catalogId=39&ID=8227

2:Cannondale Wind Aero 27.2x250mm ($40)
http://wheelandsprocket.com/itemdetails.cfm?catalogId=39&ID=3599

3:Carbon Seatpost 26.8, 27.2, 30.9, 31.6MM ($40)
http://wheelandsprocket.com/itemdetails.cfm?catalogId=39&ID=8228

PS:Im really new to the whole switching of the seatpost so i really dont even know the diameter of my own seatpost so if anybody knows it'll be a great help!!! :D

Spend a few more $$$, then get a thomson Elite

my bontrager sport seatpost doesn't slip... Probably because I'm 130 LBs though. Tighten the QR?

yea i did that but it slips as in sideways not nescessarily drops...

Put a little bit of paper as a shim? Probably be worse but you never know.

carbon? just get a normal post ... or if your current one is not carbon throw some hairspray on it ... other remedys include putting dirt on it .. teflon tape .. or removable loc tite. I currently use a 10 dollar seatpost from pricepoint .. no slipping. I had to replace my other as it was looking worn out.

My post slips too. I tried a new QR and it didnt help. My friend got a new Easton EA30 and he likes it. I might give it a try.

We have a 27.2 mm OD

The price increase of a carbon post really isn't worth it. A post weights almost nothing to begin with. The bling factor is cool, but let's be real here. If your post is slipping then it probably is too small. The QR should be able to tighten it just fine. Someone else mentioned a shim. You may need one.

I am wary of the no name carbon seat post. I have seen branded seat posts and no name carbon seat posts albeit for a roadie. The wall thickness of the no-name stuff was very, very thin. Sure it made for a lighter seatpost but then when i started reading about the failures of that given seatpost, I was pretty hesitent.

Have you checked to see what length post you need? The posts you listed (which I think are road posts) are 250mm and 300mm.. probably not long enough.

Spend a few more $$$, then get a thomson Elite

Ding ding - we have a winner! Thomson or nothing - use one and you'll know. :D

... Brad

Yeah, I'd be surprised if a 250mm post worked for you (remember that a good 80-100mm need to remain inside the seat tube). 350mm or 400 is more usual for mountain bikes with sloping seat tubes. I usually just pick something up from the shoebox in the back room of the grungiest bike store in town.

One of my earliest frustrating bike gear experiences was with a Kore Light seat post back in 1992 or so... I was trying to be a weight weenie and save 80g or so. I sheared three or four different titanium and steel replacement bolts before I finally chucked the damn thing and bought something overbuilt enough to handle actual off-road conditions.