Birdy AXS: Hubsmith Freehub Construction and XDR Freehub Body

In the previous post, I wrote about how I wanted to transfer the compatible components over from the Fnhon DB12 to the Birdy folding bike. The SRAM AXS groupset will be transferred over, but this is not so straightforward.

The SRAM Force 10-36T 12 speed cassette requires a XDR driver, which is not commonly found on small wheeled bikes. On the custom 451 wheelset by Ascent Bikes, I was lucky the Novatec rear hub has a compatible XDR freehub body which enabled the modification.

On the new Cirrus Elite 406 carbon wheelset, I checked to make sure that the Hubsmith rear hub has a compatible XDR driver, so as to use it with a SRAM cassette. The default freehub body is the Shimano HG spline design, which may be useful one day, so I will keep it around.

XDR freehub body for the Hubsmith rear hub. This is an additional part which I purchased together with the Cirrus Elite wheelset.

Birdy AXS: Ascent Cirrus Elite Carbon Wheelset (20" 406)

Finally, after thoroughly studying the Birdy City in its stock configuration, and disassembling the frameset to study the individual frame parts, I can now move on to share about the new components!

Prior to getting the Birdy City, I already had a rough idea of what I wanted to modify on the Birdy. Most of the components are decent, and would be good enough for casual riding. However, since I wanted to use the Birdy to replace my existing Fnhon DB12 folding bike, I plan to transfer most the compatible components such as the SRAM AXS drivetrain over to the Birdy.

The main major component that cannot be transferred over would be the custom 451 wheelset on the Fnhon DB12. For a start, the 451 wheel size is too big to fit on the Birdy, as it can only accept a maximum wheel size of 406, and that is with slim tires.

Next, the Birdy requires a special front hub, with inward offset hub flanges and rotor mounting. Therefore, a new wheelset is needed for the Birdy, due to the special hub design.

Whenever I want to get a new wheelset, I will always consider getting one from Ascent Bikes. I have actually gotten quite a few wheelsets from them, with some of them custom built.

1) Extra strong 20" 406 wheels custom built for the Bike Friday Haul-A-Day cargo bike.

2) Low profile lightweight 20" 451 wheels custom built for the Fnhon DB12 folding bike.

3) Zenith Elite 700C road wheelset with a quiet rear hub for the Cervelo Aspero, and later the Focus Paralane.

Therefore, I decided to get a high end carbon wheelset from Ascent Bikes for the Birdy. The model is Cirrus Elite, which comes in either 406 or 451 rim sizes, and various other hubs. In this case mine is a pretty standard configuration for Birdy bikes.

Birdy Wheelset Specifications:

Birdy compatible Hubsmith front hub and rear hub.

Quick release axles.

100 mm front OLD, 135 mm rear OLD.

Shimano HG spline on the rear hub.

Disc brake mounting (only 6 bolt is available, not Centerlock).

50 mm tall 406 carbon rims with black bladed spokes and spoke nipples.

3M reflective decals (Darklight).

The wheelset is actually hand built in Singapore, with some of the components flown in from overseas. So you could actually customize it if you wanted to, subject to part compatibility and availability. I did not have to wait long for the wheelset, it took just slightly over a week.

New wheelset fresh from Ascent Bikes!