Has anyone had luck with Pinhead seatpost clamp?

[pnwetc]

Since I already use a Pinhead skewer on my front wheel, I decided to get a matching seatpost clamp from Pinhead when I upgraded my saddle. However, I am finding that the clamp is almost impossible to tighten enough to prevent the seatpost from sliding downward under my weight after cycling a few kilometers. I will tighten as much as I can, pressing with my palm to keep the key in the bolt to avoid slippage until I am practically injuring myself, and yet the post still will not stay secured in place. I do not have this same problem with an old seatpost clamp that is tightened with an M5 bolt, nor with the quick release clamp that came with my bike.

I am using a 31.8mm clamp on my Radrunner Plus. I understand that to be the correct size for this bike, and it sure looks like it fits properly. Also, I am not especially heavy (about 73kg/160lb), so I don't think the seat is under excess pressure.

Has anyone else had success with the Pinhead seatpost clamp on a Rad bike? Am I doing something wrong, and/or is there something more I can do to make this work? Should I consider another solution for securing my seatpost instead?

[Ddaybc]

That's an interesting problem. I use Pinhead stuff on my RW4 and the seat post clamp works well. However Pinhead sent me a clamp and Pinhead fastener for the 40 mm lower seat post as it's a telescoping one. I couldn't get it tight enough and after a few moments of riding it would begin sliding. I tightened it so much I even bent the through bolt Pinhead sent me. At the moment I don't have a solution, I haven't talked to Pinhead but when I ordered the original setup they did say they are waiting for the factory to begin making the 40 mm seat post clamp again. They will let me know when they become available.

[Eric7]

Since I already use a Pinhead skewer on my front wheel, I decided to get a matching seatpost clamp from Pinhead when I upgraded my saddle. However, I am finding that the clamp is almost impossible to tighten enough to prevent the seatpost from sliding downward under my weight after cycling a few kilometers. I will tighten as much as I can, pressing with my palm to keep the key in the bolt to avoid slippage until I am practically injuring myself, and yet the post still will not stay secured in place. I do not have this same problem with an old seatpost clamp that is tightened with an M5 bolt, nor with the quick release clamp that came with my bike.

I am using a 31.8mm clamp on my Radrunner Plus. I understand that to be the correct size for this bike, and it sure looks like it fits properly. Also, I am not especially heavy (about 73kg/160lb), so I don't think the seat is under excess pressure.

Has anyone else had success with the Pinhead seatpost clamp on a Rad bike? Am I doing something wrong, and/or is there something more I can do to make this work? Should I consider another solution for securing my seatpost instead?

From the book "Zen and the Art of Motorcycle Maintenance."  Something to the effect that aluminum soda cans are made from very high quality aluminum. You can cut it to make perfectly useful shims.

[Wingnutpc]

Put a pinhead seat clamp with the largest ring this past week on my RadCity 5 and works great.