Final post for the Fnhon Ultegra Di2 12 speed folding bike! In the previous post I prepared the Ascent Cirrus Elite carbon wheelset for use on this bike. Due to the change of wheel size from 451 to 406, the gear ratio has been reduced by approximately 10%.
As the gear ratio should be carefully chosen to match the usage and rider's abilities, any significant change in the gear range will affect the suitability of the gearing. The previous gear range was 30 - 92 gear inches, which is ideal for climbing and relatively fast rides on the road.
However, changing the wheel size from 451 to 406 will cause this gear range to decrease to 27 - 84 gear inches, which does not have sufficient top speed for road riding.
Therefore, the easiest solution is to increase the chain ring size to compensate for the smaller wheel size. A Stone 46T narrow wide chain ring was used, and this will be changed to a larger 50T chain ring.
Stone 50T narrow wide chain ring. Weighs 118 grams, which is 20 grams more than the 46T version.
Compatible to Shimano 12 speed chains, and also the Shimano 4 arm road crankset BCD.
Close up look at the narrow wide teeth, for good chain retention. Chamfered teeth to reduce driving noise.
New 50T chain ring installed on the Ultegra R8100 crankarm! Along with my iconic coloured chain ring bolts.
Alongside the left crankarm
Right side crank arm with 50T chain ring weighs 480 grams
Left crank arm with crank arm fixing bolt weighs 195 grams
Total crankset weight is 675 grams, which is decent. This is the same Ultegra R8100 crankset that was on the Focus Paralane. After I disassembled that bike, I reused the components across a few of my other bikes. Now, the Fnhon Ultegra Di2 12 speed bike has a full Ultegra R8100 groupset.
After swapping from 451 to the smaller 406 wheelset, the kickstand does not work so well any more. The kickstand length is important, as it determines how much the bike tilts when parked. It is related to the wheel size, as a larger wheel diameter means that the axle height of the bike is higher.
With smaller 406 wheels and previous kickstand (optimized for 451 wheels), the bike angle is too straight when parked. This causes it to tilt over very easily.
I ordered a shorter kickstand to replace the original kickstand.
Original kickstand for 451 wheels weighs 158 grams
New shorter kickstand for 406 wheels weighs a bit less at 152 grams
With the correct kickstand, the bike leans to the side a bit more, which is what I wanted. Too little or too much tilt makes the bike unstable.
There is little space to fit a kickstand between the rear rotor and the rear wheel spokes.
With the new kickstand installed successfully, the modification of the Fnhon Ultegra Di2 12 speed folding bike is completed! Below are the pictures of the bike in its final state (I think). It has evolved a lot over the years, starting from a 11 speed flat handlebar setup with XTR Di2 components, to its current drop bar setup with 12 speed Ultegra Di2.
5 mm adapter added to push out the rotor, from the Birdy position to the standard position.
Same setup for the rear wheel, but with a smaller 140 mm diameter rotor.
Shimano Ultegra R8100 crank arm, with Stone 50T narrow wide chain ring.
Here is the refreshed drivetrain! Matte grey rims and crank arms give a different look. The rear derailleur has a custom short cage to have more ground and tire clearance.
Full bike view with high profile carbon rims but smaller 406 wheel size.
Previous setup with larger 451 wheels but low profile rims. I like both even though they give off different vibes.
All the components you see here are high end stuff!
Saved 200+ grams with these upgrades. Now the bike weight (excluding pedals and kickstand) is just 9 kg! Just slightly more than the flat handlebar Fnhon DB11 setup.
Extra pictures of the bike out for test rides. Here is the giant pumpkin at Elementum, near Buona Vista.
At the old Bukit Timah Railway Station.
