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I am about to buy a new seat post on the Internet.
Looking at the pictures, the saddle clamp has a single bolt, but I can not understand how it could adjust the saddle angle.
The seat post I currently use has these grooves on the saddle clamp, so I can adjust the saddle angle quite easily.
What are the differences between these two types?
From memory, the top seatpost has a slot on one side where the bolt passes through, which is not visible in the image. This allows a range of movement. The underside of the bolt head is either not flat, or it is in a cone-washer that conforms to a conically-sided hole.
However with two smooth sides pressing together, the only thing stopping the clamp from sliding is pressure.
Your second seatpost is "superior", though a two-bolt design leaves them both behind for strength and adjustability.
On the other hand, I rode for twenty years without any problems on a bike that had the first type of seat post My new bike had the second type of seat post and it failed within three months. The grooves wore down very quickly and then the seat would not stay in a horizontal position. On both bikes, I had the seat (same seat on both bikes) positioned towards the rearmost end of its travel, always within the range marked on the rails.
