I need to lower the seat on my Cervelo P3c. The stinkin’ seat post is so long, it’s all the way down, so I’ll need to to cut it to lower it. Has anyone done this before? Should I risk cutting it myself, or take it in to LBS? I only need to lower it maybe 1-2cm. Is it good for the seat post to be riding all the way at the bottom? Seems like it would pick up more vibration from the frame that way. Thanks!
I cut about 1.5 inches from mine w/out any issues, just make sure you
have the proper tools before you start. I used a standard hacksaw with
a blade designed for cutting carbon fiber which only cost a few bucks
at the local hardware store. If you use a regular blade you will end
up splintering the carbon fiber which could cause major issues with the
structural integrity of the seat post. Just ask someone at the
hardware store what your looking for and they can point you in the
right direction.
agree with the above. i would add a few wraps of electrical tape, it helps that blade to get going without jumping around on that nice smooth carbon…
very important: wear respiratory protection if you cut it yourself.
The post is really wide and really narrow… which side is better to cut?
start on the thickest/widest side.
I’ve cut a couple of them. Notes:
I found it works best to cut from the back end and finish at the front end. It’s too easy to get fiber “runners” finishing up on the pointier end.
Wrap masking tape in the area you want to cut and mark your cut line on the masking tape. Cut with a fine-toothed hack saw. A blade designed for metal cutting will work (high tooth count per inch), or a carbide blade.
You’ll note that the uncut seatpost has a notch cut out of the back edge. I’ve always replicated that notch. It makes it a whole lot easier to get the seatpost into the seat tube. Cutting that notch is the last step.
It’s not difficult. Just remember the golden rule … measure twice, cut once. 
Awesome. Thanks for the pointers er’body. I’ll be sure to be super careful, and not snort the carbon-fiber shavings when I’m done. I’ll post a “critique my seat height” thread when I’m finished. Er, maybe not.
i wrapped the post above the cut line with tape and used a dremmel with a cutting disc … not much dust at all, zero splinters and easy.
Were you able to get a super straight line with the dremmel? Seems like that cutting disc is so small, it’d be hard to get a straight line like a hack saw would. Does a straight line even matter?
it was straight enough … there was a slight wobble to at one point in the cut … but it was surprisingly easy to keep straight once the disc was through … regardless, it’s hidden 4" inside the frame …
P3C seatpost cutting project was a success. I used Tom’s method (Dremel Tool), as I didn’t feel like going back out to the hardware store to buy a hacksaw. I taped up the seatpost with masking tape and carefully measured and marked up 1-inch all around the tape. The Dremel went through it like butter, and I somehow managed to make a perfect cut. So now my seat is lower (which is a good thing I think), and I didn’t ruin my cervelo seat post. psycholist, I didn’t see the notch, so maybe this post has been cut before? I also wore a surgeon’s mask and my cool daddy sunglasses - which I’m sure was a funny sight for 10PM on a Friday night.
Guys, thanks for your input on this! -Nick