An Even Longer Seatpost An Even Longer Seatpost Parts Needed We're going to turn the original post upside down, cut off the bevel and cut a notch in it for clamping. Then we'll fit a clamp and assemble it all. You'll need : ? Seat post clamp to fit a 1 1/8" tube ? 25.0mm seatpost If you use a Twenty clamp, you'll have to shim it down to 1 1/8". For tools, you'll need: ? a hacksaw ? drill ? 3/16" bit ? center punch ? round file ? flat file ? tool to tighten the new clamp as required. 164952646 Modify Original Post Start by cutting about " off the bottom of the original post. We have to eliminate the bevel. Wrapping a piece of masking tape around the tube will help you make a nice straight cut. File the end and around the outside edge to eliminate sharp burrs. 164952647 Slot the Post, 1 Next, about 7/8" from the end, drill a 3/16" hole in the post. This is best done with a drill press, but you can do it if you're careful with a hand drill, center punching it to keep the bit in place. This length will leave enough room on the post to fit a Twenty clamp, if you have one or can obtain one. I plan to do this someday, but for now I'm using a clamp left over from a recumbent project. 164952648 Slot the Post, 2 Now cut a notch from the end of the post to just off-center of the hole. Make a second cut as close to the first one as you can without it cutting into the previous notch. It will leave about 1/2mm of material which will fall out when you finish the second cut. 164952649 File the Post's Inside Be sure to file the burrs off the inside of the post, for a good fit and so you don't scratch the inserted post. This is especially important if it's an alloy post (which is all I could find.) 164952650 Assemble the Post All that's left is to assemble the works. Put the clamp on the original post, insert the 25mm post and snug up the clamp to hold it in place for now. The fit of this is just a little looser than ideal, but it's close enough to clamp well. 164952651 Install the Seat Next, mount the seat as usual on the top half of the post assembly 164952652 Install on the Bike And put the assembly in the bike. Adjust for length. I tried to get about the same amount of post inserted in each stage, but as long as you have a good minimum insertion in each clamp, you'll be fine. My consulting structural engineer (my son, also a Twenty owner) says that the design of the Twenty frame is plenty strong enough to deal with a longer post. Well, presuming you aren't too far into the Clydesdale Class that is. If you are a bigger person, I'd suggest you investigate a strut of some sort. If you loosen both clamps, the seat will still collapse all the way into the frame. And if you ever want to remove the telescoping post, the original seatpost can still be returned to normal use by removing the extra bits and returning it to its right-side up position. With what you trimmed and the notch, it'll effectively be an inch shorter, but turn the slot to the back and it will be quite useable for all but the taller riders. 164952653