Birdy AXS: Tire and Rotor Setup

Since I will be changing the wheel size on the Birdy from the stock 18" 355 to the new 20" 406, I will also need new tires and inner tubes. For 20 inch 406 tires, there are lots of choices as it is a very common tire size.

The limiting factor here is the frame clearance during folding, and the rear derailleur cage clearance during riding. I understand from others' experience that for this larger 20" 406 wheel size, I cannot use a tire that is too wide, as it also makes the tire outer diameter too big for proper folding.

My preferred tire for 20" 406 is the Schwalbe Kojak 35-406 tire that is 35 mm wide, as it provides the best balance between comfort and rolling resistance. However, it seems that this tire width may be too wide to be used on the Birdy. The next best option is thus the Panaracer Minits Lite tire, which comes in a slightly narrower 32-406 tire size.

I have used this tire previously in the narrower 28-451 size, on the Dahon MuSP and also the Fnhon DB12. The 32-406 size was briefly used on the Dahon MuEX many years ago, but it was replaced as it did not feel suitable at that time.

Panaracer Minits Lite folding tires.

Latex and TPU Inner Tubes

In the earlier post on the Specialized Aethos, I introduced the Dura-Ace C36 wheelset, which is lighter in weight than the Dura-Ace C50 wheelset. This time, I still chose a normal clincher type of tire, which means that an inner tube is required. The Continental GP5000 tire is available in both tubeless and tubed type depending on the rider's preference.

The C36 wheelset is tubeless ready, with rim tape already installed. This setup can be used for both tubed and tubeless tires. Since I am using a tubed setup, I would need to select inner tubes for this wheelset.

Previously I have been using normal butyl inner tubes, such as those from Schwalbe. They work well, however there are now alternatives that has some advantages over normal butyl tires.

Butyl inner tubes are cheap and relatively durable, but have more rolling resistance and weigh more. The air retention is good compared to other types. It is the safe but boring option.

Latex inner tubes are a bit more expensive, and are rather fragile. The rolling resistance is very low, about the same as using a tubeless setup. The weight is about 30% less than butyl, while the folded size is about the same as butyl. Biggest disadvantage of latex inner tubes is the poor air retention, as the air pressure can drop drastically over a day. It is usually necessary to pump the tires just before going for a ride.

TPU inner tubes are relatively new, but they have the potential to become an excellent option. They are the most expensive type for now, although they are also more durable than latex tubes. Rolling resistance is also low, although not as low as latex tubes. Weight can be 1/3 that of butyl, while the folded size is reduced by half. Air retention is acceptable as it can last a few days before needing a top up.

From left to right, TPU vs Latex vs Butyl inner tubes.

TPU tube is about half the size of the other two types, which makes it ideal for packing as a spare.