Yes Bigcheese is correct. You most likely cut your seatpost too short. It was suppose to be cut within 5mm's of your typica seat height. Then you were to use the 1mm, 2mm, and 5mm spacers that fit into the bottom of the seatpost before installlation. The spacers should have been included with your frame. If you have cut the seatpost too short, try re-using the extra seatpost you cut off as extra large spacers if you really need the extra height.