One of the first upgrades many people embark with on their Brompton is to replace the seat post with titanium. The main reason for many is to reduce the weight (steel seat posts are heavy) and for some, ride quality. I've been using a generic titanium seat post for a while, but I was never pleased with how bouncy titanium seat posts are. When you pedal fast and hard, you'll know what I mean. This bouncing and bopping leads to efficiency loss.
So I swapped out my titanium seat post for an Aceoffix aluminum seat post to try something else. It was cheap ($23 with shipping) on AliX, so not a big financial hit. I like the flexibility of the Brompton pentaclip, and this specific seat post allows it to be re-used. Other seat posts I've seen have integrated seat rails, but have various pros and cons. I also didn't want to go the carbon fiber route for various reasons, such as price vs performance and safety.
After waiting a week for the seat post to arrive, I got around to installing it yesterday and went for a several mile ride. My first thoughts are wow – this seat post is super stiff. While it eliminated the seat bounce I referred to, you can feel the bumps on your ass.
An added benefit of the aluminum seat post is it's not much heavier than titanium. A titanium seat post weighs 267g. A Brompton OEM seat post weighs 390g. The Aceoffix aluminum seat post weighs 300g. A 90g weight saving over the steel seat post ain't bad for only $23!
Also, a nice feature of this seat post are the numbered markings. It also has rough textured finish, presumably to mitigate seat post slipping.
The colour I've purchased is black matte. I also ordered a silver matte for my C line.
Long term we'll see how it fares, but for its price vs performance, I don't think you can go wrong if you want something lighter weight than steel, but stiffer than titanium.
by versello