BMW 4 Series (425i) Big Brake Kit Upgrade / TTSPORT Classic 9040 & 6411
BMW's 4 Series carries a lower stance, a wider track, and stiffer suspension bushings than its 3 Series sibling — a car with real cornering intent that deserves brakes to match. This 425i's owner wanted more pedal feel and more stopping power than the factory setup could deliver, so the shop went with a TTSPORT front six-piston / rear four-piston big brake kit built specifically for it.
The build: a TTSPORT TT9040 six-piston caliper and 355x32mm high-carbon heat-treated slotted rotor up front, paired with a TT6411 four-piston caliper and 355x28mm drilled rotor plus stainless brake lines out back. The whole setup is tucked behind the car's factory 20-inch wheels.
Vehicle & Kit Specs
| Item | Specification |
|---|---|
| Vehicle | BMW 4 Series (425i), 20-inch wheels |
| Front caliper | TTSPORT TT9040 forged six-piston, opposed pistons, dust boots |
| Front rotor | 355x32mm high-carbon heat-treated drilled rotor |
| Rear caliper | TTSPORT TT6411 four-piston caliper |
| Rear rotor | 355x28mm high-carbon heat-treated drilled rotor |
| Lines | TTSPORT stainless steel brake lines (rear) |
Sprinting from 0-60 in the mid-7-second range with a nose-down, fastback stance, the 4 Series carries plenty of speed into corners. A brake system that only just handles daily driving isn't enough margin for a car built to be pushed, which is why the shop specced this front-six/rear-four combination rather than a rotor-only upgrade.
Why It Works
- The TT9040 front caliper body is forged from high-strength aluminum alloy rather than cast, which flexes less under hard braking — that rigidity is what gives the pedal a firmer, more predictable bite instead of a spongy stroke.
- Larger 355mm rotors front and rear (32mm front, 28mm rear) carry more thermal mass than the stock discs, so they absorb more heat before fade sets in on repeated hard stops.
- The rear TT6411 setup was reported to run smooth and linear with no vibration or noise — a sign the rotor and pad contact is even and the hardware is properly matched to this chassis.
- This kit was confirmed to clear the car's factory 20-inch wheels, so there's no need for spacers or a wheel swap to run it.
Installation Gallery
What TTSPORT brake components were installed on this BMW 425i?
What wheel size does this setup clear?
What is the front caliper made of?
Need fitment confirmation? Choose the closest TTSPORT series or send your vehicle, wheel size, and intended use before ordering.