If you’re a car enthusiast, you’ll know that upgrading your ride isn’t just about boosting power under the hood—it’s about creating a unique presence. The M135i is already a fantastic machine, but it just looks so bog-standard, for the average Joe you would not be able to tell it has a 3L N55 6-cylinder turbocharged engine.
This was my second BMW, but really the first that brought me into the world of really modifying my car. Carbon Accents was really born from this car, sparking an interest in car styling, modification and making your car unique and stand out on the road. I had to go all out and that involved putting on a full-on carbon fibre body kit. This build serves as a great example of how you can make a stock car really stand out.
From small tweaks that make a big impact to major body upgrades, here’s a detailed breakdown of every modification we made, why we chose them, and how they’ve turned this M135i into one that we are proud of.
Small Mods
When it comes to car modification, the devil’s in the details. Sometimes, the smallest changes can completely redefine the personality of the car.
We started with some affordable and easy-to-install mods that make a huge difference in the car's aesthetics.
Gloss Black Front Kidney Grille:
One of the first things people notice about a BMW is the iconic kidney grille.
By replacing the stock chrome grille with a gloss black front kidney grille, we immediately gave the M135i a more aggressive, modern look. We gave it that ‘shadow edition’ stealth look
We used this one: 1 Series - F20/F21 Facelift LCI: Gloss Black Double Slat Grill 15-19
The black finish contrasts perfectly with the car’s overall design, making the front end feel sportier and more refined.
The gloss black grille is a quick, easy modification that gives the car an upgraded appearance without the high price tag of other mods. It’s one of those simple touches that makes a world of difference.
M-Style Carbon Fibre Mirror Covers:
Mirror covers might seem like an odd thing to mod, but when you think about it, they’re one of the most visible parts of the car. We swapped the stock mirror covers for M-style carbon fibre mirror covers to give it that M look.
We used the 1 Series - F20/F21: Dry Carbon Fibre M Style Wing Mirror Covers 11-19 for this mod.
Carbon fibre is often associated with race cars, and these mirror covers bring that aesthetic to the M135i.
Dynamic Indicators:
Next up, we installed dynamic wind mirror indicators. These indicators don’t just blink—they light up in a sweeping, sequential pattern that makes the car stand out, especially at night. Often you only saw the sweeping indicators on VW but now they are everywhere.
For this mod, we used the 1 Series - F20/F21: Dynamic Mirror Indicator Lights 12-19.
While this may seem like a minor modification, it’s all about the details. Dynamic indicators add a subtle, sophisticated touch to the car's lighting setup and elevate its overall appearance, replacing the old halogen indicators with LED.
These indicators also have a tinted/smoked design which also gives a cleaner and stealthier look. It’s one of those features that people might not notice right away, but once they do, they’ll appreciate the added finesse.
Carbon Fibre Antenna Cover:
We didn’t stop at the mirrors and grille; the carbon fibre antenna cover was a perfect little touch to enhance the overall look of the car. Stock antenna covers are typically plastic and can look a bit bland, but the carbon fibre version brings a level of sophistication and sharpness to the car’s profile.
For this one, we used the 1 Series - F20/F21: Carbon Fibre Antenna Trim.
It’s a small modification, but when combined with the other carbon fibre elements, it gives the car this special vibe. Plus, it's a direct replacement, so there's no complex installation process.
Aesthetic Upgrades
Once we had the small visual tweaks done, we moved on to the larger, more impactful upgrades.
These mods don’t just look great—they also improve the car's aerodynamics and handling. If you’re serious about modifying your car, these are the kinds of upgrades that truly elevate both form and function.
Carbon Fibre Rear Boot Spoiler:
A rear boot spoiler isn’t just about looks—it’s about improving the aerodynamics of the car at higher speeds. The carbon fibre rear boot spoiler that we chose helps with downforce, keeping the rear of the car more stable as it cuts through the air.
We used the 1 Series - F20/F21: Gloss Black 3D Style Spoiler 12-19 for this mod.
In terms of aesthetics, this mod gives the M135i a sportier, more aggressive profile. Carbon fibre is a lightweight, high-performance material, and using it for the spoiler ensures that the car’s handling remains sharp while achieving that race-ready look. This isn’t just a cosmetic upgrade; it has practical benefits too.
Gloss Black Rear Canards:
The gloss black rear canards were another crucial addition. These little aerodynamic pieces attach to the corners of the front bumper and are designed to direct airflow around the car, reducing drag and improving overall downforce.
We used the 1 Series - F20/F21 Facelift: Gloss Black Maxton Rear Side Splitters 15-19 for this mod.
At higher speeds, these canards help keep the front of the car planted to the road, giving it better stability and grip. The visual impact is undeniable—these canards have a sleek, aggressive appearance that adds an extra layer of motorsport-inspired appeal to the front end.
Gloss Black Front Splitter:
The front splitter is a mod that slightly improves aerodynamics while also providing a more aggressive look. The splitter extends from the front bumper and helps to channel air underneath the car, improving airflow and reducing lift.
For this mod, we picked the 1 Series - F20/F21 Facelift LCI: Gloss Black Splitter 15-19.
This mod can significantly improve high-speed stability by keeping the front of the car more grounded, particularly on fast straights or when braking hard.
Carbon Fibre Rear Diffuser:
Moving to the back of the car, the carbon fibre rear diffuser is an essential piece in improving airflow beneath the vehicle.
Here, we used the 1 Series - F20/F21 Facelift: Carbon Fibre Rear Diffuser 15-19.
This mod complements the other carbon fibre elements of the car, making the rear look more dynamic.
Carbon Fibre Side Skirts:
Side skirts might seem like a subtle mod, but they play an important role in managing airflow along the sides of the car. These carbon fibre side skirts reduce turbulence and prevent air from getting trapped under the car, improving stability and downforce at higher speeds.
We used 1 Series - F20/F21: Carbon Fibre Side Skirts 12-18.
Visually, they help lower the car’s profile, making it appear wider and more aggressive. These side skirts are a great way to enhance the car’s appearance, and when made from carbon fibre, they help keep weight down while achieving that aesthetic we’re looking for.
Carbon Fibre Exhaust Tips:
Last but not least, we added carbon fibre exhaust tips to the rear of the car. These tips don’t just look good—they’re part of the overall theme of making the car more aggressive and race-inspired.
Here, we used the 1 Series - F20/F21 M135i/M140i: Carbon Fibre & Chrome M Performance Exhaust Tips 12-19.
The carbon fibre finish ties in perfectly with the other mods and adds a touch of class to the exhaust system. It gives it the M-Performance look without spending so much money on a full exhaust system.
Wheels: A Key Part of the Transformation
Wheels set the tone for any car, so we swapped out the stock ones on the M135i for satin black alloys. Properly transformed the stance—looks absolutely spot on now.
We use the 1 Series - F20/F21: 18" Satin Black 'M3 CS 763M' Style Alloy Wheels 11-19 for this mod.
These wheels are lightweight, which helps with handling, and the satin black finish adds a touch of sophistication. The design of the wheels is aggressive yet clean, making them the perfect complement to the car’s carbon fibre body kit.
And honestly, they’re quite capable of withstanding the horrible UK roads without any issues, at least big ones.
Tuning and Performance Upgrade
BMW N55 engine has a world of power. In the M135i it is really tuned down.
When you consider that it's the same engine as you find in the F87 M2 and F26 X4 M40i, you might start thinking about unleashing its full potential.
The N55 can be remapped to unlock a world of power; that’s why we opted for an easy-to-use ProTuning Freaks Bootmod3, which boosts it to about 390-400 bhp. This upgrade remaps the car's ECU (engine control unit) to optimize various parameters like air/fuel ratios, ignition timing, and boost pressure.
Crazy for a small hatchback.
You can use this without any additional parts to upgrade, like I did. But in hindsight, I would strongly recommend upgrading the charge pipe. I had the unfortunate experience of mine snapping off, leaving me worried that my engine had blown. It’s actually a well-documented issue with the N55 in the online community.
Final Words
The BMW 1 Series (F20 LCI M135i) is already a great car, but with the right modifications, it can become something truly special. By starting with small, cost-effective upgrades like the gloss black kidney grille and dynamic indicators, and moving on to more significant mods like the full carbon fibre body kit, and the power boost, we’ve transformed this M135i into a visually striking, performance-enhanced machine.