folding bicycles

Dahon 2009

Dahon Jetstream rear Airshock

Here we have some pretty substantial shock information from the Dahon engineering department.
Most shocks are designed to perform at its optimal level with 15~25% sag. By sag we mean the travel done just by the rider's weight when sit with normal riding position at rest. To measure sag level we usually:
1. figure out the amount of sag in mm. A 15% sag of a 30mm travel shock is simply 4.5mm.
2. pump up the shock to a random level, say, 80psi.
3. position the o-ring so it's at the very top and in contact with shock body.
3. gently sit down on the bike without exerting additional downward force.
4. gently get off the bike
5. now the o-ring should have been displaced from its original upmost position due to weight alone; we measure this distance between o-ring and the shock body.
6. if this distance is smaller than 4.5mm (15% sag), lower the pumped pressure. Vise versa.
7. repeat above procedures until the desired sag level is reached.

In experience, a 65Kg rider needs about 70psi on this particular bike (Jetstream P8). And this number really is rider dependent and requires trial-and-error adjustment.

here more info which makes the terminolgy easier to understand.

1. Eye-to-Eye, or ETE, is the default, uncompressed, length between the centers of two mounting holes. Some standard lengths are 150, 165, 190, 200mm, etc. Our particular shock on the Jetstream is a 150mm.
2. As far as our bike is concerned, relative dimensions are 150mm ETE, 24mm bolt length, and 8mm bolt OD. By bolt length we really meant the width of bushing on the shock. This bushing is frame/shock specific and can be replaced with a different size when needed.
3. We use Loctite when mounting the shock as factory default.
4. This is info for '09 X-Fusion shock from Tech department. On the manual it suggests a normal range of pressure between 100 - 250psi (However, our frame is rather special to have short chain length so this number is pretty much irrelevant). And a maximum of 300Psi should never be exceeded according to the Manufacturer. These values are pretty typical for most suspension brands.
5. The pump used to fill up the shock is usually a high pressure 300psi pump. Normal pump wouldn't be able to reach such high pressure and is hard to precisely control the flow of air.

hope all this info helps to make an even great bike even better