Saturday, September 30, 2006


A Folding Seat

I decided to try to replace the standard seat on my A-Bike for somthing more comfortable. I decided that the new seat should not weigh much more than the standard seat, and the folded size should not be affected very much. Ultra lightweight bike seats and seatposts are easy to obtain, but they greatly increase the folded size of the bike.

After looking around at various seat options, I decided that if the seat could fold, then it would have a minimal effect on the folded size.

I bought an ultra light-weight seatpost, an X-Lite metal matrix. This post is one of the lightest post available, being made of some exotic aluminium composite material. This post also allows the seat angle to be adjusted over a very wide range. After removing the two titanium pinch-bolts on the post, I replaced them with a pair of quick-release cams, threaded onto M6 threaded rods, cut down to size. The result is shown in the pictures below.

Here you can see the seatpost with the quick-releases, installed where the titanium pinch bolts used to be. This seat is definitely heavier than the original A-Bike seat, although a high-end carbon/titanium seat would minimize the difference. The seatpost is also heavier than the stock post, but not by much.

Here is another view. I could not get two quick-releases in the same colour!

With the quick-releases undone the seat tilts forwards very easily. However the seat rails are still held tightly, so the seat does not slide forwards or backwards - the only motion is the seat tilting. So with the quick-releases closed, the seat does not move.

Here is a view with the bike folded.
The seat sticks out about two inches (5cm) more than the original seat.

So there it is. Advantages are that you can have the seat of your choice with a longer seatpost. Disadvantages include a slight weight increase, a slight increase in folded size, and there is an extra step to folding/unfolding.

It remains to be seen whether the seat will slip in the long term. These seatposts are not designed to be regularly adjusted. This seatpost also has a 27mm setback, which makes the folded size a bit larger. Although not shown in the photos, I have since added a cable-tie under the seat. The cable-tie is adjusted in length so that it only allows the seat to tilt back to a predetermined angle. So unfolding is now easy, I do not have to manually level the seat, just unfold it until the cable-tie becomes taught.

Hi, I want to replace the seatpost and seat too ! Which post length is fit for A-bike ? 270mm or 340mm ?
thanks ~~~~ I am Roy, from Hong Kong.
Wow! A-Bike is cool, but with this new seat it's a non plus ultra!!!

Amazing stuff, and quite nice blog!

BellaG., from Italy.
Cool new seat! Who's the manufacturer, model, etc? Thks.
Who's the manufacturer, model, etc? Thks.
I just ordered a A-bike copy with the 8" wheels. I live in Canada. I would like to try to break this record of 50 km at some point. I like to see how this bike does on a ride far longer then the bike was designed for. I have already bought the replacement seat for my bike so the original seat will not be used.
Hi, your seat mod is very well done. I got a 8" wheel A-Bike and found it fun to ride but the seat is just too small. I would like to the the same mod, can you tell me where to get a quick release. Thanks michael
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