A slipping seatpost can ruin any ride. You’re riding along quite happily when you hit a pot hole or a section of rough road and your seatpost drops. Even if it’s just by a few millimetres it will be immediately noticeable and you’ll want to pull over to sort it out.
Most of the time this is will just be due to one of the bolts at the seat clamp coming use, so it can be fixed with an Allen key in just a couple of seconds. However, sometimes the problem is more persistent and certainly shouldn’t be solved by just tightening those bolts ever further.
The first step is to take the seatpost out and give everything a good clean, and also apply grease the bolts in the seat clamp. However the most important thing is to take your seatpost and (whatever material it is made out of) give it a liberal application of carbon-fibre assembly paste. Not only will this help to stop the seatpost from slipping, but it will prevent it from seizing inside the frame.
When you’re retightening the seat clamp you don’t need to do the bolts up to the maximum recommended torque; only go as far as is necessary to hold the seatpost in place. And if after all that you’re seatpost is still slipping, it’s worth investing in a seat clamp with two bolts for a little more security.