Bestrider Pump Pro 20: 10 Speed Drivetrain

When I was deciding on the drivetrain to use on the Bestrider Pump Pro 20, there are many considerations, since this is a kids bike. The stock drivetrain has a 8 speed semi-Shimano drivetrain, which is actually pretty good for kids bikes. However, I wanted something nicer than the 8 speed drivetrain.

On the previous Bestrider Pump Pro 16 kids bike, I took extra effort to make sure that the 3 speed drivetrain is easy to use even for kids. It was a unique, one-of-a-kind 3 speed drivetrain for 16 inch kids bikes. Now, on this new 20 inch kids bike, the shifters will be changed from the Revoshifter (good for small hands) to a more standard trigger shifter.

One of the prerequisite to operate a trigger shifter is a hand size that is big enough and strong enough to push the shifting levers. Usually, this only becomes feasible from the age of 6 onwards.

Another important feature for kids is the Optical Gear Display (OGD) on the shifter. This helps them to know which gear they are in, and understand how to shift gears depending on the terrain. Problem is, many high end flat handlebar shifters (such as 11 speed road or MTB shifters) do not come with OGD. Whereas for other shifters such as the Sora 9 speed shifter, it has an OGD but no numbers on it, which is basically pointless. The stock Shimano Altus SL-M310 8 speed shifter is actually good because it has gear numbers clearly shown on the OGD.

If possible, the shifting force and shifting stroke for kids should be minimized, to make it easier for their small hands and short fingers to push the shifting levers. From what I know, to have shorter shifting stroke, a high end shifter such as Deore XT or XTR will be ideal. At the same time, the shifting force will also be lower as the construction uses sealed bearings inside for smoother operation.

Thus, I was looking for the best shifter that fulfills all these conditions:

1) Light shifting force

2) Short shifting stroke

3) Optical Gear Display with numbers

The ideal candidate for this is thus the Deore XT SL-T780 Trekking 10 Speed Shifter. This model has been out of production for many years, but I still have it from old stock. It was first used on the Polygon Cozmic CX3.0 MTB, then the United Trifold when I was experimenting with multi-speed drivetrains.

Deore XT SL-T780 Trekking Shifter for 10 speed MTB drivetrains. Rare item nowadays!

I like that each gear position is accurately indicated by a silver line.

Premium aluminium lever. It has Instant Release, 2-Way Release, and Multi-Release features, which is not necessary.

Weighs 126 grams without the shifter inner cable.

Since I have decided to go with this 10 speed shifter, I have to find the other 10 speed components to match the shifter. This includes a 10 speed cassette, 10 speed MTB rear derailleur, and a 10 speed chain. It is harder to find high end 10 speed MTB components nowadays, since MTB drivetrains have mostly moved to 11 and 12 speeds a few years ago.

Therefore, once again I need to look towards older models for high end 10 speed components. 10 speed MTB components are available at a few levels, such as Deore, SLX and Deore XT. I chose to get a Deore XT cassette to save a bit of weight, and to have a more corrosion resistant cassette.

Deore XT CS-M771-10, which is a 10 speed cassette. I got the 11-36T cassette for a wider gear range, and to be compatible to the rear derailleur as shown below.

Nice and shiny new cassette! I like the sand blasted finish which gives it a premium look.

Larger sprockets are 36T, 32T, 28T and 24T, which are nice gear steps.

Being a Deore XT cassette, the largest 6 sprockets are mounted on 2 aluminium spiders to save weight.

Close up look at the larger sprocket set, with 28-32-36T sprockets.

Next 3 sprockets are also mounted on a spider to save weight.

Entire 11-36T 10 speed cassette weighs 308 grams, which is pretty good.

In order to match the 10 speed shifter that I have chosen, I need to find a compatible 10 speed rear derailleur. As the shifter is a MTB / Trekking type of shifter, I need to use a MTB or Trekking 10 speed rear derailleur, due to the cable pull ratio.

If I just get a standard 10 speed MTB rear derailleur, the cage will be too long for small wheel bikes. A 10 speed road rear derailleur such as Tiagra or the older 105 is not compatible, which is a shame since those road rear derailleurs have short cages which are ideal for small wheel bikes.

Using my previous experience with the United Trifold, I know that there are short cage 10 speed MTB rear derailleurs, such as the Shimano Saint or Zee. I no longer have the Saint rear derailleur, so I had to buy a new one. Decided to get the Zee rear derailleur instead, and managed to find a brand new unit even though it has already been discontinued.

Shimano Zee RD-M640-SS Short Cage 10 speed rear derailleur. There are two specifications, and I needed the one with a larger 36T rear sprocket compatibility to match the 11-36T cassette.

Brand new Zee rear derailleur! Shadow construction for a low side profile.

Uses a stamped inner link, instead of an aluminium version on the Saint rear derailleur.

It is also equipped with a one-way clutch with on-off switch, to minimize chain slap on bumpy terrain.

Check out the super short cage! Only compatible with front single drivetrains.

Cage length is only 50 mm from pulley to pulley, which is way shorter than even Dura-Ace and Ultegra road rear derailleurs.

Weight is 267 grams, which is pretty chunky for a short cage. This is due to the beefy construction to make the derailleur more resistant to knocks and bumps.

I realized that there is no need for the one-way clutch feature, since this kids bike is not going off-road on bumpy terrain. Same as what I did for the Saint rear derailleur on the United Trifold, I also removed the clutch unit.

The one-way clutch parts can be removed, leaving this area empty. It will still work perfectly fine, just without the clutch feature.

Clutch parts removed from the Zee rear derailleur.

After removing the clutch parts, about 16 grams is saved. Weight is reduced to 251 grams.

Main purpose of removing the clutch is not to save weight, although that is a nice bonus. Rather, the main objective is to reduce the shifting force. As the clutch inadvertently provides resistance during inwards shifting, this translates to a higher shifting force. By removing the clutch, the rear derailleur cage is able to rotate more freely, with just the spring force and no clutch resistance. The result is lighter shifting force at the shifter, which is the main objective.

Birdy AXS: Chain Length, Freehub Grease and QR Axle Changes

Final post on the Birdy AXS 12 Speed folding bike! At least for now, until some new project or ideas pop into my head.

Throughout the whole upgrading process from the stock 9 speed Birdy City, I have learnt a lot about the Birdy folding bike. Especially for the folding design, where it is different from any other bike.

There were a few issues which were not fully resolved earlier, but they have now been fixed. 3 of the problems have been highlighted below, along with how I solved them.

First issue was the chain length on the Birdy drivetrain. As I transplanted the SRAM AXS 12 speed drivetrain from the Fnhon DB12 folding bike, I reused the existing chain as the mileage was quite low.

However, the chain stay length of the Birdy is longer at 430 mm, compared to the 400 mm of the Fnhon DB12. Therefore, using the same chain length with the same cassette and chain ring, on a longer chain stay, makes the rear derailleur cage stretch out too much.

At the largest sprocket (lowest gear), the rear derailleur cage is very stretched out and looks over the limit.

XTR and Deore XT Trail Pedals: M9020 vs M9120, and M8020 vs M8120

Previously when I was just a beginner SPD user, I prefer the use of pedals with SPD on one side, and a flat platform on the other side. This allows me the flexibility to use SPD shoes or normal flat shoes on the same bike, depending on the type of ride. My favourite pedal is the PD-A530, which has been replaced by PD-EH500.

More recently, I realized that on some bikes, I will only ride them while wearing proper cycling shoes, which in my case means SPD shoes. This applies to almost all my full sized bikes, such as the Focus Paralane commuting bike and the Cervelo Aspero gravel bike.

In those cases, there is no need for a flat platform side on the pedal. Rather, it is best to have SPD on both sides of the pedal, so that I can clip in easily regardless of the pedal orientation.

After the bike fitting done at LOUE Bicycles, I eventually decided to use pedals of different stack height on left and right sides, in order to balance out the unbalanced leg length and hip rotation.

That is how I eventually ended up with so many different pedals, as I only need one side of pedal from each set, to get different stack heights. Anyway this gives me a chance to compare all these different pedals.

XTR PD-M9020

XTR PD-M9120

Deore XT PD-M8020

Deore XT PD-M8120

Packaging for the newer XTR and Deore XT pedals

Deore XT M8020 vs GRX ME700 SPD Pedals

One of the most durable SPD pedals you can find is the Deore XT SPD pedals, where it is tough and literally unbreakable, unless you are involved in a heavy crash where the pedal is the least of your concerns.

It is not as expensive as the XTR version, but is probably more durable as it is not as lightweight as the XTR version. That said, it may still be a bit too costly for some, so there is a cheaper version, the newly launched GRX ME700 pedals.

These ME700 pedals are loosely associated with the GRX gravel series, although it is not tagged as part of the GRX groupset. It is basically a non-series dual-sided SPD pedal that looks very similar to the PD-M530 pedals.

PD-ME700 with a bold edgy appearance.

Weighs 240 grams on one side, giving a weight of 480 grams for a pair. The claimed 540 grams on the website is wrong.

Deore XT PD-M8020 is lighter at 200 grams per side, giving a weight of 400 grams per pair. Quite a significant difference. XTR PD-M9020 is even lighter at 372 grams per pair.

Side by side comparison. The platform on the ME700 is bigger, but this also means higher weight.

Usable platform width on the ME700 is wider, due to the larger platform and also the different axle design.

The Deore XT pedal has a sleek pedal axle design which I value very much, compared to the cheaper design which tends to collect dirt easily.

Platform on the ME700 is wider, and note the difference in axle design.

Finally, the ME700 uses a smaller Size 6 Allen key, while the Deore XT axle takes a Size 8 Allen key instead.

The Deore XT pedal can ONLY be installed with the Size 8 Allen key, while the ME700 pedal can either be installed with a Size 6 Allen key or the standard 15 mm pedal wrench. I prefer installing pedals with the size 15 pedal wrench, as it is easier to tighten and loosen the pedals, compared to using an Allen key.

However, in this case the aesthetics of the higher end pedal axle wins out for me, as I much prefer the slim and clean looking axle on the Deore XT and XTR pedals, instead of the other axle design.

Given a choice, I would choose the Deore XT or XTR pedals every time, just because of the axle design, unless there are other factors involved. Function wise, I think the ME700 pedals would be just as good as the Deore XT version, just with a less premium appearance.

United Trifold: Saint Rear Derailleur and 10 Speed Cassette

Since the mid cage 105 R7000 rear derailleur is not suitable for the United Trifold, I had to find another set of components which will better suit the small wheeled bike.

The problem I faced previously was insufficient ground clearance, as the mid cage rear derailleur had a rather long cage. Therefore, I decided to get a rear derailleur with a really short cage, to solve this problem completely.

What I know is that the Saint or Zee rear derailleurs from the downhill groupsets have the shortest cage, which is why I decided to try the Saint rear derailleur on the United Trifold.

However, as the Saint rear derailleur is a 10 speed component, this means that I need to change the cassette and shifter to a compatible 10 speed type. For convenience's sake, I will continue to use the 11 speed chain first. The chain ring and crankset does not affect compatibility.

Saint RD-M820 rear derailleur

Super low profile! Barely sticks out from the side.

Really long inner link arm, as the cable pitch for MTB is longer than road. The high and low limit screws are located far apart from each other.

Super short cage! I forgot to measure the length, but it is really short. Definitely no problem with ground clearance.

As a MTB downhill component, it comes equipped with a clutch. Nice to have but not necessary.

Weighs a pretty chunky 271 grams, due to the extra robust construction for downhill riding.

Side by side comparison with the previous R7000 mid cage rear derailleur.

Big difference in cage set length and also inner link length.

Here is a 11-28T 10 speed cassette, similar to what I used many years ago on the Dahon Vitesse 2x10 speed setup.

105 5700 11-28T 10 speed cassette weighs 249 grams

Installed onto the wheelset with no issues. A 1.85 mm + 1 mm spacer is needed at the back of the cassette.

Looks good on the wheelset!

Next, I need a 10 speed MTB shifter, as it needs to be compatible to the 10 speed MTB Saint rear derailleur. A Tiagra 4600 road flat handlebar shifter is not compatible due to the different cable pitch.

Deore XT Trekking SL-T780 10 speed shifter, which I used many years ago on the Polygon Cozmic MTB.

Upon installation of the rear derailleur to the bike, I found that there was quite a bit of friction from the clutch unit, even though the clutch was turned off. Therefore, I opened up the clutch to take a look. Here is how you can service your clutch too!

How it looks with the internal clutch unit removed from the rear derailleur.

Here is the clutch unit. It can be serviced or replaced if it is faulty.

Then, I realized that the rear derailleur will function perfectly fine without the clutch unit. As I don't need the clutch function, I decided to just remove the clutch unit, allowing the rear derailleur cage to swing smoothly, and also reducing the shifting force.

Once the 10 speed shifter has been installed onto the bike, along with the other 10 speed components, I took the bike for a test ride!

A derailleur drivetrain looks good on the bike!

Lots of ground and tire clearance, due to the super short cage Saint rear derailleur.

The whole bike looks good in the sun. Purple and yellow colour combination is weird but really outstanding.

Went to the same step that caught the R7000 rear derailleur previously. No issue this time!

Good clearance for the rear derailleur cage.

The optical gear display on the shifter is good as well, due to the clearly defined gear indication.

Can clearly see which gear I am currently in, and how many more available on either end.

Based on the test ride, this 10 speed setup has passed with flying colours! However, I also need to check how well it works when it is folded. Due to the short cage, it is expected that the chain would become even more slack when the rear triangle is folded down.

When folded, the short cage barely takes up any slack chain.

Due to this, the chain becomes way too slack, as the chain is long enough to touch the ground already.

As the chain is way too slack when folded, it will touch the ground, which is not acceptable for me. Also, due to the short engagement between the chain and cassette when folded, the chain is likely to drop off the cassette when the bike is unfolded again.

Therefore, even though this 10 speed drivetrain rides really well, it is not good enough due to the poor chain management. I need to keep trying alternative ideas that will work better.