Fnhon DB12: XDR Freehub Body

For this conversion of the Fnhon from 1x11 speed to 1x12 speed, the most critical factor is whether I can fit a 12 speed cassette onto the rear hub. There are various 12 speed cassettes, but not all are suitable.

The most common 12 speed cassettes are MTB cassettes, with a large 10-50T or 11-50T, just to list a few examples. However, these are way too big for small wheeled bikes.

As for 12 speed road cassettes of smaller sizes, it is hard to find, except for Campagnolo or SRAM cassettes. To me, Campy is like a niche manufacturer, although they are considered one of the big three alongside Shimano and SRAM. There might be a few other even more niche manufacturers that I do not know of.

That leaves the SRAM 12 speed road cassette as the only viable option (Shimano 12 speed road was not launched yet at this point). This means a XDR freehub body is necessary, to install the 10-36T 12 speed cassette shown in the previous post.

Which was why, before I bought any more new components, I needed to check if the freehub body on my wheelset can be changed or not. To recap, the 451 wheelset on my Fnhon is a custom wheelset, as I could not find a lightweight, Centerlock disc brake 451 wheelset on the market.

Rear hub on the wheelset is a Novatec D412SB-CL, where CL stands for Centerlock.

After doing some research, I found that there are variants of this hub, where the freehub body is the XD or XDR type, instead of the Shimano spline type that I have. This means that it is very likely that the freehub body on this rear hub can be swapped to the XDR type.

I managed to find a replacement freehub body on Lazada, using the limited info from the seller and also my existing hub. Basically it looked like there was a good chance it would fit, so I took a gamble and bought the XDR freehub body which is claimed to be compatible to my current Novatec hub.

Existing 11 speed road freehub body on the Novatec rear hub.

The new XDR freehub body! Last I searched, it is no longer available from the same seller on Lazada.

To remove the freehub body, this end cap/lock nut has to be removed.

Looks a bit different, let's see if it can be swapped successfully.

Original freehub body removed! Ratchet can be seen here.

Once one side of the locknut is removed, the other side slides out together with the axle.

The spacers are of different length, between these two freehub bodies. The longer spacer is for the Shimano spline freehub body.

The Shimano spline freehub body is longer, as the spline engagement stretches all the way to the 11T sprocket.

From another point of view, most of the sprockets on the XDR cassette do not engage the freehub body directly, but are joined to each other instead.

Shimano spline freehub body and spacer weighs 85 grams.

SRAM XDR freehub body and spacer weighs exactly the same. I always hear that the XDR freehub body is lighter, but it is not the case here.

Testing the XDR freehub body on the original axle

Taking the chance to service the rear hub, by cleaning and adding new freehub grease on the pawls and ratchet. Refer to previous PZ Racing and Wheelsport wheelsets.

I tried to reassemble the freehub body, but found that the freehub body could not seat fully into the hub. I panicked a little as I thought it might be incompatible.

Upon closer inspection, I found that there was an extra seal on the freehub body. When I removed the original Shimano spline freehub body, the seal remained on the hub shell, but I did not notice it (refer to picture above showing internal ratchet). The XDR freehub came with its own new seal, which I also didn't notice. So, when I tried to install the XDR freehub body onto the hub shell, there were 2 seals which caused the interference.

Original seal on the left, and the new seal on the right which comes with the XDR freehub body.

Once I took out the extra seal, the freehub body and other parts went on with no problem.

The hub worked normally, and was able to spin smoothly with and without engaging the freewheeling function. I'm glad that I was able to swap the freehub body on this Novatec freehub! Many thanks to Ascent Bikes for choosing a good and widely compatible hub for building this custom wheelset. If not for this swappable freehub body, this 12 speed conversion project would not have been possible.

SRAM Force 10-36T 12 speed cassette. As mentioned in the cassette post, this is a really good ratio to provide a wide gear range and also reasonably small gear steps.

New 12 speed cassette looking good.

The reason why the XDR structure allows a 10T smallest sprocket is due to the smaller integrated lockring (using same lockring tool), and the absence of spline engagement for the smaller sprockets.

If a conventional lockring was used, the diameter would be too big to fit a 10T sprocket.

So far, the 12 speed cassette and the XDR freehub body have been successfully installed on the existing 451 wheelset of the Fnhon folding bike. This has to be the most doubtful part of the modification, as the other components (rear derailleur, shifter, chain) will probably not pose an issue.