Bmw Z4 vs Porsche 911
On MOT-testable defects, the Porsche 911 (fail rate 9.7%) performed better than the Bmw Z4 (17.1%) across comparable years. The biggest divergence was suspension, where the Z4 recorded failures more often.
17.1%
Z4 fail rate
9.7%
911 fail rate
7.42pp
Difference
Side by side
| Metric | Bmw Z4 | Porsche 911 |
|---|---|---|
| MOT tests analysed | 203,942 | 251,987 |
| Pass rate | 82.9% | 90.3% |
| Fail rate | 17.1% | 9.7% |
Where they differ
| Category | Z4 | 911 |
|---|---|---|
| Suspension | 5.7% | 1.6% |
| Visibility | 3.3% | 0.0% |
| Brakes | 4.8% | 2.0% |
| Tyres | 5.1% | 2.3% |
| Emissions & environmental | 0.0% | 1.9% |
| Lighting & signalling | 5.4% | 4.8% |
Methodology & source. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-01. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.