Fnhon Gust: Bike Geometry

The Fnhon Gust 16 inch folding bike has been completed successfully, even though a few problems were encountered along the way. This bike has a beautiful frame which impressed me. A high end drivetrain was supplied, which I installed onto this bike.

Let's check out this bike and some of its dimensions.

Full bike view, looks very good with black frame and components, with a bit of gold accents.

Dura-Ace 9000 components helps to reduce the weight of the bike and elevate it to premium status.

Some bike geometry that I will measure will be the chainstay length, wheelbase, and bottom bracket height. These values will affect how the bike rides, which will surely be different from a full-sized bike with different geometry.

Chainstay length is only 347 mm.

Chainstay length is measured from the centre of the bottom bracket to the centre of the rear axle. This Fnhon Gust has a really short chainstay length, as it is usually 400 mm or more, even on 20 inch folding bikes. The Java Freccia carbon mini velo has a chainstay length of 380 mm, which I thought was already quite short.

If the chainstay length is very short, it will be less stable when travelling fast, although it will also be very nimble for navigating tight areas. For this 16 inch folding bike, which is not meant to go fast, it will probably be OK.

A short chainstay length also means that the chain angle will be quite extreme at the top and low gears. This will likely cause excessive chain noise, and even poor shifting performance. If you backpedal when in the lowest gear (largest sprocket), most likely the chain will fall off the sprocket. This is the same issue which I encountered on the S-Ride 12 speed 11-50T cassette.

Next, the wheelbase is measured. This is the distance between the front axle and the rear axle, which also contributes to stability. A long wheelbase is stable, but also less maneuverable.

Wheelbase is a relatively short 910 mm.

A normal road bike has a wheelbase of about 990 mm or more, so this Fnhon Gust has a really short wheelbase. 

The bottom bracket height is the distance between the ground and the centre of the crankset spindle. A low BB height is good for stability, but there is also increased chance of pedal strikes. On the other hand, a high BB height gives good ground clearance, but cornering feel will not be as good due to the higher centre of gravity.

Bottom bracket height is about 298 mm, which is pretty average. Nothing of concern in this case.

I found that for my height of 168 cm, with inseam length of 78 cm, I needed the seatpost to be fully extended, right at the limit line. In other words, if you have longer legs, you will not be able to extend your legs fully, as the seatpost does not go any higher. You will need to get a longer seatpost in this case. This is one disadvantage of having a small bike frame, where the seat tube is short and the seat post clamp is low.

Seat post insertion depth is at the minimum. In other words, this is the highest the seatpost can be safely used.

Finally, I measured the wheel diameter of this 16 inch, 349 wheelset. 349 mm refers to the diameter of the rims, but it increases once the tire height is added. In this case, 32-349 Schwalbe Kojak tires are used.

Wheel diameter is 420 mm.

The overall bike length (front tire to rear tire) is thus wheelbase plus wheel diameter, giving an overall bike length of 910 + 420 = 1330 mm. This is really short and compact, as a normal full sized road bike has a length of around 1800 mm. The Bike Friday Haul-A-Day cargo bike has a slightly longer length of 1870 mm.

In summary, this is a compact and agile bike, which makes it fun to ride as it can navigate around tight corners easily. However, travelling at high speed will be less stable due to the short wheelbase. Even without folding, the overall length is short which makes it easy to store. I think it can go straight into the backseat of a car, just by folding down the handlepost.