Bicycle Mechanics - slipping seatpost

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rwing6
07-10-10, 11:29 PM
the seatpost on my super pista is slipping down as i ride. the seatpost is fine (thompson elite) i can find any problem with the frame, and the bolt tightens fine. does anyone know what would be causing this? the post is the right size this problem just started happening after about 500 miles

electrik
07-11-10, 12:26 AM
Maybe the seatpost is crumpled a bit, is the clamp clamping? is the seat-tube still squeezing down as evidenced by the notch? It could be that you've worked it into an oblong shape instead of the circular shape if you rode with the seatpost above minimum insertion..
cyclist2000
07-11-10, 12:45 AM
I had a similar problem and it was the binder bolt.

sevenhills
07-11-10, 01:45 AM
u could drill a small hole in the seat-post, at the ideal hieght, and put a small pin/screw in it? Not tried this myself.
Torchy McFlux
07-11-10, 01:58 AM
Slipping posts are almost always due to them being the wrong size for the frame. The Bianchi Super Pista needs a 27.2, I believe. First thing you should do is verify that.
reptilezs
07-11-10, 06:03 AM
somewhat common with thomson's. if using a qr clamp replace it with one that has a brass or bronze bushing instead of the nylon or go to a bolt on non qr collar
rwing6
07-11-10, 11:21 AM
its the right size post, it was way below minimum insertion, not a quick release, ill check the binder bolt i guess, it still tightens down but i guess it could be loosening as i ride
reptilezs
07-11-10, 12:59 PM
you can try flipping the collar so that the slots are opposite of each other. also make sure not too much grease is on the post.
dperreno
07-11-10, 06:43 PM
you can try flipping the collar so that the slots are opposite of each other. also make sure not too much grease is on the post.

Yes, I was having the same problem with my Thomson, I wiped most of the grease off (and switched to a bolt-on collar) and it stopped slipping.