Sunday, March 24, 2024

Birdy AXS: Installation of Multi-S Fork Pivot on Birdy

In the earlier post, I shared some information about the new sealed bearings pivots for the Birdy. Now, I will be installing them onto the Birdy Fork, in an attempt to improve the front suspension smoothness of the Birdy AXS.

Previously I had already dismantled the Birdy front fork completely, so I am familiar with the structure. The stock pivots can be removed easily, so that is no problem.

Stock pivots on the Birdy front fork. Note that it has self-loosened, as it is only kept in place by Loctite.

One problem with the stock Birdy pivots is that due to the nature of the bushing construction, the tightness of the rotation torque is mainly dependent on how tightly you clamp the 2 halves of the pivot. If it is too tight, the whole joint is jammed and does not rotate. If too loose, there will be axial free play. Therefore, it is necessary to adjust the clamping such that there is minimal looseness. The pivot is only held in this orientation by liberal use of Loctite on the screw thread, as the pivot is not completely tightened in this condition.

Stock pivots removed from the fork.

This sealed needle bearing has to fit inside the fork.

Here are the outer plates of the pivot.

Sealed needle bearing will be pressed into the centre section of the pivots, into the stock plastic bushing.

Overall view of the new pivot. The 2 ends with shoulders will rest inside the outer plates, while the needle bearing will be inside the middle section. In this setup, the pivots can be fully tightened as it bottoms out against the ends of the sealed needle bearing in the middle.

It's quite a tight fit to ensure no radial looseness, so it cannot be pushed in by hand.

Using the bottom bracket press fit tool to help press in the new bearings.

Needle bearings installed after much work. At this point I thought of reverting to the stock pivots, but I'm already at the point of no return.

With one side of the pivot shaft installed. Note how the female part of the pivot (not shown) will rest inside this area of the fork.

The needle bearing is pressed into the centre section of the fork by press-fit. Any rotation will be between the inside of the needle bearing and the centre shaft of the titanium pivot.

The width of the fork legs don't really match up nicely, there is some offset which means poor pivot alignment.

One thing which I overlooked is the front hydraulic hose routing for the front brake caliper. The length and routing has to be precise, to prevent overbending or pulling on the hose during folding and unfolding.

Previously, the hose will slide over the flanges of the pivot, since the flanges are chamfered. However, this new titanium pivot has square shoulders, which tend to catch on the hose during folding and unfolding.

Hydraulic hose tends to catch on the shoulder of the pivot, so it needs to be adjusted manually during folding and unfolding.

Hydraulic hose is still routed the same way, on the inside of the front fork.

New Multi-S pivot installed

The pivots protrude more from the fork legs (both inwards and outwards) compared to the stock pivots. Not really an issue though.

Close up view of the new pivot.

Observations of the new pivot:
1) Square shoulder of the pivot catches on the front hydraulic hose during folding and unfolding.
2) Additional weight even with titanium parts, as stock pivot is aluminium.
3) Difficult installation with press fit tools required.
4) No improvement in stiction reduction due to misalignment of the fork legs.
5) Can tighten fully without jamming the pivot joint.

My verdict: Don't waste your money or your time installing the sealed bearing pivots. Due to the misalignment of the fork legs, there is no improvement in the smoothness of the pivot joints. Only benefit is that you can tighten the pivots with higher torque to prevent self-loosening, since the sealed bearing in the middle prevents the joint from being jammed.

Some pictures of the Birdy AXS below!

Along the Kallang Park Connector Network, watching the sunrise, with the National Indoor Stadium in the background.

With Marina Bay Sands and the Singapore Flyer in the background!

Birdy AXS: Multi-S Sealed Bearing Fork Pivot

If you have modified a bike suspension before, you would know that good pivots use sealed bearings to enable smooth rotation even when under load. On the Birdy AXS, the front suspension pivots use bushings instead of sealed bearings, as it is much cheaper to implement. However, I found that the rotation is not so smooth, due to the friction in the bushings. Any friction means that the suspension will be less responsive, as it has to overcome stiction (look out the suspension term on Google).

Most people upgrade the suspension of the fork, from the stock coiled spring to an air or coil spring with damper. In my case, I was happy with the basic coil spring design of the stock suspension. Besides, this gives the lightest configuration.

However, I was curious as to whether the pivots can be upgraded to be smoother. I came across this sealed bearing replacement for the front suspension pivots of the Birdy, thus I decided to give it a try and see if it really makes a difference. Note that this is different from the common ColorPlus pivots which is still a bushing, and is mainly just a cosmetic difference.

Front suspension pivot replacement for Birdy front forks, by Multi-S.

Titanium pivots! Price is in Renminbi, so it is quite expensive. Somehow still cheaper than ColorPlus pivots...

Laser etched information on the pivots.

Here are the parts for 1 pivot. Each set comes with 2, for both sides of the fork.

CNC machined part, with some description shown below based on what I think. 

Referring to the picture above, from left to right: Male screw thread tightens to other side of the pivot. Centre portion is where the sealed bearing will slide over. Right side shoulder with the short pin as the key slot to prevent rotation.

Tightens with a normal Allen key.

Other side of the pivot is mainly just a nut with a female thread.

Nicely machined and finished.

Sealed needle bearings to allow smooth rotation between the inside shaft (not installed) and outside cylinder face.

Many narrow and long needles act as the bearings with high load capacity.

One pair of the pivots, for 1 bike, weighs 56 grams.

In contrast, the stock pivot bushings are lightweight at just 22 grams, as they are simpler and made of aluminium.

In the next post, I will show how the pivot replacement will be done, and whether it is worth changing to the sealed bearings or not.

Sunday, November 19, 2023

Ultegra Rear Derailleur: R8000 (Mechanical) vs R8050 (Electronic)

Here is another component comparison! I love doing side by side comparisons as it is interesting to spot the differences and try to understand why they are designed differently.

This comparison is between two Ultegra derailleurs of the same 11 speed generation. R8000 is the mechanical 11 speed rear derailleur, while R8050 is the Di2 11 speed electronic rear derailleur.

For this generation of Ultegra components, they are designed so that the mechanical and Di2 versions look similar, with the same design language. Other than the functional and dimensional differences, the visuals will be kept similar.

R8050 Di2 rear derailleur was removed from the Dahon MuSP, when it was modified from Ultegra Di2 11 speed to Sora 1x9 speed.


R8000 on the left with visible cable adjust bolt. R8050 on the right with the servo motor.

Saturday, November 18, 2023

Ultegra Di2 Shifters: ST-R8050 (Mechanical) vs ST-R8070 (Hydraulic)

Shimano makes so many different types of road shifters that it is often hard to tell which model is for which kind of drivetrain. For braking, there are mechanical rim brakes and hydraulic disc brakes, while for shifting, there is mechanical shifting or electronic shifting.

In the previous generation of 11 speed drivetrain, there are 4 types of Ultegra shifters.

ST-R8000: Mechanical shifting, mechanical braking
ST-R8020: Mechanical shifting, hydraulic braking
ST-R8050: Electronic shifting, mechanical braking
ST-R8070: Electronic shifting, hydraulic braking

Today, I will compare R8050 and R8070, which are both electronic Di2 shifters, but with different  types of braking. I have this chance to do a direct comparison because of some related bike projects.

Some time ago, I converted the Focus Paralane all-weather road bike from 11 speed to 12 speed, thus the ST-R8070 shifters were removed from the bike.

Then, the Dahon MuSP was downgraded from Ultegra Di2 11 speed to a mechanical Sora 1x9 speed drivetrain. The ST-R8050 shifters were removed from the Dahon MuSP.

With these two shifters in hand, I can do a direct comparison before selling them away.

Can you guess which is which? For this generation of shifters, all 4 models were designed to look and feel similar.

Friday, November 17, 2023

Folding Bike 3-way Component Swap

This was a relatively complex bike modification project, as it involved 3 different bikes with many different components. Main reason for all these swapping is to upgrade to the latest components, and sell away the older and more basic components.

Flowchart showing the bikes before the component swap.

After the component swap

Saturday, November 4, 2023

Fnhon Ultegra Di2 12 Speed: Geometry Comparison with Aethos

With the Fnhon Ultegra Di2 12 speed folding bike completed, I will now compare it with the Specialized Aethos. Reason for this comparison is to show the differences in geometry between an standard full-sized road bike and a folding bike with drop bars.

Before comparing bike geometry, align the bottom bracket, as this is the datum for all other bike measurements.

Both the saddles are adjusted to my height, but the Fnhon saddle is taller, as the bottom bracket is higher from the ground.

Saturday, October 14, 2023

Fnhon Ultegra Di2 12 Speed: Assembly Part 1

With all the problems solved as described in the earlier posts, the assembly of the new Fnhon Ultegra Di2 12 speed can now begin! I usually wait until all the required parts are available before I start building, instead of building half way and then waiting for the rest of the parts.

First step is to install the new Ultegra R8100 11-34T cassette onto the wheelset. This is the same custom built wheelset by Ascent Bikes, and with the same Panaracer Minits Lite tires as used previously.

Ultegra R8100 11-34T 12 speed cassette installed!

Using the new XTR MT900 rotors, same as the ones which I am using on the Focus Paralane.

Sunday, October 8, 2023

Fnhon Ultegra Di2 12 Speed: 12 Speed Cassette, Chain and Chain Ring

After solving the issue of the Di2 battery mount on the Fnhon frame, and modifying the Ultegra R8150 rear derailleur cage to a shorter version, I am almost ready to start assembling the bike.

The drivetrain and shifting components on the Fnhon Ultegra Di2 12 speed folding bike are mostly new, except for the Ultegra R8000 crank arms which will be carried over from the Dahon MuSP. I did not get a new Ultegra R8100 crankset to match the rest of the Ultegra R8100/R8150 groupset, as I only need the crank arms and not the chain rings. Therefore, it is more than good enough to reuse the R8000 crank arms on the new setup.

Let's start with the cassette. A 12 speed road cassette is needed for the Ultegra Di2 12 speed setup, and I can choose between a 11-30T cassette or a 11-34T cassette. On the Specialized Aethos and Focus Paralane, which have front double drivetrains and are dedicated road bikes, I chose the 11-30T cassette for its tighter gear spacing.

However, for this new Ultegra Di2 setup on the Fnhon, it will be a 1x12 speed front single setup. Therefore, the gear range will be decided by the range of the cassette, while the chain ring will shift this gear range higher or lower. I decided to use the wider range 11-34T cassette on the Fnhon Ultegra Di2 12 speed folding bike.

I actually had a Dura-Ace CS-R9200 11-34T 12 speed cassette as a spare, but decided not to use it on this bike. Instead, I decided to get a new Ultegra CS-R8100 11-34T 12 speed cassette, to match the rest of the components and also to do a comparison with the Dura-Ace cassette.

Dura-Ace vs Ultegra 11-34T 12 speed cassettes.

Saturday, October 7, 2023

Fnhon Ultegra Di2 12 Speed: Short Cage Conversion using Ultegra RD-R8000

Although I managed to install the Mr TiParts super short derailleur cage onto the Ultegra Di2 RD-R8150 12 speed rear derailleur earlier, it was not a satisfactory modification. There were too many issues with the modifications that can affect the performance.

Therefore, I continued to look for a better solution to have a shorter cage rear derailleur on the Fnhon Ultegra Di2 12 speed folding bike. Then it occurred to me that I should consider original Shimano rear derailleur cages that are shorter, instead of third-party ones.

Drawing from previous experience when I modified the GRX rear derailleur with an extra long cage for the Cervelo Aspero gravel bike, it may be possible to find a compatible shorter cage to replace the stock cage on the Ultegra RD-R8150 rear derailleur.

After removing the Ultegra Di2 RD-R8050 11 speed rear derailleur from the Dahon MuSP, it was available for comparison. All R8000 and R8050 mentioned below are the short cage SS version.

Long outer plate of Ultegra R8150 vs the shorter outer plate on Ultegra R8050 11 speed rear derailleur.