The X4M F98 build and parts list
| Component | STOPFLEX X4M F98 spec | What it does for the car |
|---|---|---|
| Vehicle | BMW X4M (F98) | Application-specific, bespoke big-brake conversion |
| Front package | Brembo GTR 6-piston billet caliper + 405mm STOPFLEX carbon ceramic rotor | Big front thermal capacity and a stiffer, more stable pedal under hard braking |
| Rear package | Rear dual-caliper setup: Brembo GTR 4-piston braking caliper + separate parking-brake caliper, 380mm STOPFLEX carbon ceramic rotor | Matched rear upgrade that keeps the factory electronic parking brake working |
| Pads | STOPFLEX high-performance ceramic pads | Normal-temp friction above 0.4μ with very low brake dust |
| Wheel requirement | 21-inch wheels | Needed to clear the large rotors and motorsport calipers |
| Fitment | Custom bracketry, bespoke install | Engineered for the X4M, not a universal bolt-on |
Confirm two things before you order: your exact 21-inch wheel has to clear the 405mm front rotor and GTR caliper at the barrel, and the rear is a dual-caliper design built to preserve the X4M's electronic parking brake. Wheel size alone doesn't guarantee fit; barrel shape and spoke clearance still decide it.
What the upgrade changes on this car
| STOPFLEX feature | Why it matters on the X4M | What you notice |
|---|---|---|
| Carbon ceramic rotors, about half the weight of same-size steel | The X4M is a heavy, fast SUV, and every kilo at the rotor is unsprung mass the suspension has to manage | A nose that turns in a little quicker and a calmer ride over broken pavement |
| Friction holding near 0.3μ at 900°C | Repeated high-speed or downhill stops heat-soak a steel setup fast on a car this quick | The pedal stays firm deep into a hard run instead of going long and vague |
| Brembo GTR billet calipers | Billet bodies flex less than cast under heavy clamp loads | A more solid pedal and finer modulation when you're really leaning on the brakes |
| STOPFLEX pads with friction above 0.4μ at normal temps | You still drive this thing on the street most days, so cold bite and dust matter | Strong everyday stopping with very little dust on the wheels |
| Non-rusting rotor surface and crackle-texture ceramic coating | An X4M gets washed and rained on like any daily, and steel rotors rust the second they sit | Clean rotor faces behind the spokes and a finish that still looks sharp months in |
What gets better
- Lower unsprung weight at all four corners for sharper response
- Heat resistance that holds pedal feel through repeated hard stops
- Very low brake dust when paired with STOPFLEX pads
- Rotors that don't rust after rain or a wash
- Street life of roughly 250,000 to 300,000 km when you stay off the track
What to confirm first
- Your exact 21-inch wheel clears the 405mm front rotor and GTR caliper
- Rear is a dual-caliper layout to keep the electronic parking brake working
- Barrel profile and spoke clearance, not just wheel diameter
- How you actually drive: street, fast road, mountain runs, or track days
If you're not sure your car matches the spec shown here, send us your wheel and build details and we'll confirm BMW X4M F98 fitment before you order through our BMW CCB collection.
Build gallery
X4M F98 brake FAQ
Why use the Brembo GTR billet caliper on the X4M?
The GTR is a billet aluminum caliper, so it flexes less than a cast caliper when you load the brakes hard. On the X4M that translates to a firmer, more consistent pedal and cleaner modulation during repeated high-speed stops, plus a more serious big-brake look behind the wheel.
How does the rear conversion handle the X4M electronic parking brake?
The X4M runs an electronic parking brake, so the rear is built as a dual-caliper setup: a Brembo GTR four-piston braking caliper plus a separate parking-brake caliper that keeps the factory EPB working. It is engineered around the car's rear architecture, not treated as a generic caliper swap.
Will this kit clear factory 21-inch wheels?
It is built for 21-inch clearance with custom bracketry. Because the 405mm front rotor and motorsport caliper sit close to the barrel, you should still confirm clearance against your exact wheel design and barrel profile before ordering.
Can a carbon ceramic setup like this handle daily driving?
Yes. A street-driven X4M gets lower unsprung weight, strong heat resistance, very low dust with STOPFLEX pads, and rotors that do not rust after rain. Cold bite is normal even around -20°C on the first stop, so it stays livable on the road.
What do you gain over a steel rotor setup?
Lower rotor weight, far better resistance to heat saturation, minimal brake dust with the matching pads, and a surface that does not rust. For street use, STOPFLEX carbon ceramic rotors can last roughly 250,000 to 300,000 km when the car is not run on track.
