After joining, I'm writing for the first time after only lurking.

I'm sharing my experience hoping it will be helpful to those who, like me, are considering entering the world of electronic shifters with value for money in mind.

There's a lot I want to convey, but since I'm not good at writing, I borrowed help from Jeminai. It's still a bit long though, so I appreciate your patience.

1. Installation Cost

a. Purchase and Installation:
On May 1st during the sale period, I purchased the L-TWOO ER9 product for 560,000 won and installed it on a 2022 Giant Propel.

b. Installation Method
I DIY'd by purchasing tools and grease from AliExpress. The manual is in Chinese and English, and although I gave up on translating it due to my poor Korean, the difficulty level is not as high as expected, so it's worth self-installing. There are installation videos on YouTube, so you can refer to them.

c. It seems I spent about 50,000 won just on purchasing tools and grease.
d. Changes in the 2026 Model:
I've also seen reviews of people purchasing it for around 400,000 won on the internet, but there have been model changes since 2026.
The old model charges from the rear derailleur with a dedicated cable, but the new model has been improved with a Type-C charging port on the front derailleur.

2. Shifting Trouble and Gear Ratio After Self-Installation
a. Shifting Feel
Since I've never used electronic shifters from other brands, it's difficult to make an objective comparison, but there were no overall shifting issues.
However, since I'm a beginner at self-maintenance, fine-tuning is a bit tricky, so currently I'm taking time to fix only the specific section where the chain drops and using it.
b. Compatibility and Function
According to the official specs on the website, it supports up to 32T, but it operates without problems on the current 34T sprocket.

c. Gear Protection Function
In extremely non-recommended gear ratios (such as front inner + rear full inner), there was noise and trouble, probably due to chain length issues.
To prevent this, I'm using the app's 'Gear Protection Function' turned on.
(When this function is enabled, entry to the rear outer 2 sprockets when the front is inner, and the rear inner 2 sprockets when the front is outer, are automatically blocked.)

3. Brake Bleeding Work and Precautions (Must Read)
a. Workability
In addition to the oil cap on the lever, there's an 'air vent (air release) cap', so bleeding feels easier than expected.
After completing the bleeding and riding a few times, if you open the air vent cap, you can see that the brake oil level has decreased.
This is where tiny air bubbles that haven't escaped gather, so it's good to refill the oil once more with a syringe.
b. Caution for Parts Loss
I lost the air vent screw during bleeding and couldn't ride for a while. If it were a typical Shimano part, I could get it easily, but
as you know, since this is a product sold only in China, there's no domestic distribution network, so it takes quite a while to get parts.
Since it's sold individually on AliExpress, I strongly recommend purchasing extra air vent screws and bleeding screws for your peace of mind. I didn't do that and suffered greatly for my mental health.(...)

4. Brake and Rotor Performance (Subjective Review)

a. Pad Contamination
The oil got on the pads since I didn't remove them during bleeding. Even after burning and cleaning them, and breaking in on downhill slopes,
the noise reappeared during the next ride, so I eventually replaced it with a Shimano Ultegra caliper.
(When I asked Jeminai about this, there was mention that luck plays a role.)
I tried to apply only Shimano pads to save costs, but Shimano pads are not compatible with the ER9 original caliper.

b. Braking Power Comparison
After using a 105 caliper, I briefly used an L-TWOO caliper and currently use an Ultegra caliper, and I can feel the difference in braking power.
Ultegra grips much stronger, and subjectively, my perceived performance was in the order [L-TWOO ≒ 105 < Ultegra].

5. Dedicated Application and Cycling Computer Integration
a. Dedicated App
Since it's my first electronic drivetrain, it's difficult to compare with other apps, but fine-tuning and various function settings are intuitively possible on a smartphone, so
there was no inconvenience in use.
b. Cycling Computer Integration
I'm currently using Wahoo Bolt 2 and gear shift status is displayed normally. However, the speed at which it's reflected on the screen after shifting is
slow. Since it's a page I don't use much, it's hard to say it's a disadvantage for me

c. Auto Trimming
When I checked the latest app update, a feature called 'Auto media marcha' was added. When I activated it, the auto-trimming function on the front derailleur
works normally.

6. Precautions During Assembly

a. Front Caliper Bolt Length
I'm not sure if it's only the Giant Propel model, but the front brake caliper mounting screw length is slightly longer than the bracket thickness.
If you tighten it all the way, it can damage the carbon layer, so you need to carefully check the depth during installation. Fortunately, I discovered it at the point where the paint was slightly scratched and took measures.

b. Caution for Thread Damage (Stripped Threads)
The air vent screw has poor durability and wears very easily. I have a memory of stripping a 105 lever by tightening the bleeding screw too hard, so I worked carefully, but still got stripped threads. It's not to the point where it can't be used at all, but
it's very annoying. You should handle it much more gently and tighten it carefully than you think for your peace of mind.

c. Battery Installation Problem
The battery holder doesn't fit due to the narrow seatpost on the 2022 Propel. This seems to be a common problem for aero models.
I removed the case from the battery holder, wrapped the outside with heat shrink tubing, and inserted it into the seatpost.
Since it's not a structure where moisture enters anyway, and even if it did, it would be blocked by the heat shrink tube, so no problems are expected.
Using heat shrink tubing, it fits perfectly without any gaps, allowing installation without a bracket.
I'm not sure about models from 2023 onwards, but for the 2022 model, this was the best solution.

d. Grommet
The 2022 Propel has 2 holes that need to be sealed. These are where the front derailleur power cable and rear derailleur power cable come out. For the front derailleur cable hole, you can use a typical Shimano product, but the grommet for the rear derailleur cable is hard to find and ridiculously expensive. Usually it comes with the bike purchase, but I didn't know I would go electronic and lost it due to improper storage(...) So I just bought a similar-sized cap from AliExpress, drilled a hole, cut it, and inserted it instead of a grommet and finished it. It doesn't stand out and isn't important, but there's no sense of incongruity. If you want to get one, you should find and use a 8mm cap.
I bought 8.5mm and it didn't fit well, so I cut it and used it.

e. Battery : The product requires 2 pieces of 14500 batteries and 2 pieces of CR2032 coin batteries to operate.
1) You must use a 14500 battery without a protection circuit. The ER9 itself has a built-in protection circuit, making it unnecessary, and
more importantly, if there is a protection circuit, the length becomes longer and won't fit in the battery holder.

2) However, under domestic law, it is illegal to sell products without a protection circuit to consumers, so it's difficult to find. AliExpress orders are not recommended as
shipping takes too long.

3) The best way is to purchase a regular 14500 protected battery domestically and then remove the protection circuit yourself.
There are many related videos on YouTube, and you can remove it by hand more easily than you think.