FIGURE 1 // WHERE IT WEARSMercedes-Benz B-Class
Top three failure systems, annotated from 62 failed first-time tests. Arrows point to where the defect is found on the car.
A Mercedes-Benz B-Class's brakes barely fail; its tyres pick up the bill
397 inspections in a single year make the B-CLASS a modestly documented electric car in the data. Tyres cause 36.6% of its failures; suspension take 1.9× the share they take on petrol and diesel cars of the same age.
First-time test findings
The seven-year vs nine-year picture
AT SEVEN YEARS OLD11.2%
B-CLASS failure rate. Petrol cars of the same age fail 14.9%.
AT NINE YEARS OLD15.9%
B-CLASS failure rate, against 19.9% for petrol.
The Mercedes-Benz B-Class fails 15.6% of first-time inspections. By 8 years that reaches 17.4%. Tyres cause 36.6% of its failures.
FIGURE 2 // SUSPENSION ARM AND BUSH25 certificates in 2024
The joint that wears out first
Suspension take 25.2% of the defects that fail this car, 1.9× the share seen on petrol and diesel cars of the same age. The most common item in that group is "A suspension joint dust cover missing or no longer prevents the ingress of dirt etc", recorded 25 times in 2024.
SECTION // SUSPENSION CONCENTRATION
Where it concentrates
The B-CLASS stays under the petrol fleet at every age we can measure. What it does fail on is unusually concentrated.
Source: DVSA MOT defect items, 2024 test year.
What to check
Check tyre age and tread across the full width, inner edge included. Electric cars wear tyres faster; a cheap mismatched set on a used car tells you how it was run. Have the suspension joints, bushes and springs checked on a lift. On this car it is a leading cause of failure and it is not visible from the outside. Check the washers reach the screen. It fails the test and it is a thirty-second check. Ask for the full MOT history by registration on the free DVSA service: advisories are next year's failures.
3 inspection points:
✓ Tyre inner-edge wear and age
✓ Suspension joints and bushes on a lift
✓ Washer reach
FIGURE 3 // FAILURE RATE BY AGEvs petrol, diesel and all electric cars
Points hidden where fewer than 50 cars of that age were tested. Dashed lines are the same-age petrol and diesel fleets.
Data sheet
- Inspections
- 397
- Passed
- 325
- Failed
- 62
- Passed after repair
- 10
- Failure rate
- 15.6% (all EV 12.0%)
- Average age
- 7.9 years
- Best year
- 7 yrs · 11.2%
- Worst year
- 8 yrs · 17.4%
- Top cause
- Tyres 36.6%
TABLE 1 // WHAT FAILS, BY SYSTEMshare of failing defects
| System | This car (mark = petrol/diesel) | Share | vs petrol/diesel |
|---|---|---|---|
| Tyres | 36.6% | 1.5× more | |
| Suspension | 25.2% | 1.9× more | |
| Brakes | 7.6% | 2.5× less | |
| Visibility | 9.9% | in line | |
| Lighting | 13.0% | 1.3× less | |
| Steering | 0.0% | in line | |
| Body | 3.8% | in line |
TABLE 2 // TOP DEFECTS ON THE CERTIFICATE
- A tyre seriously damaged26
- A suspension joint dust cover missing or no longer prevents the ingress of dirt etc25
- A rear registration plate lamp or light source missing or inoperative in the case of a single lamp or all lamps14
- A tyre cords visible or damaged11
- Windscreen washers not working or not providing sufficient fluid to clear the windscreen6
- A suspension pin, bush or joint excessively worn6
Wording as printed by the tester, from the DVSA inspection manual.
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Where it holds up
- Brakes fail less often than on petrol and diesel cars (7.6% of defects vs 18.7%)
- Steering fail less often than on petrol and diesel cars (0.0% of defects vs 3.1%)
Where it fails
- Tyres take a bigger share of failures than on petrol and diesel cars of the same age (36.6% vs 23.7%)
- Suspension take a bigger share of failures than on petrol and diesel cars of the same age (25.2% vs 13.6%)
VERSIONS SEEN IN THE TESTSas recorded
- B-CLASS397
OWNER REPORTS // MATCHED TO RECORDED DEFECTS0 read · 0 matched
No owner discussion has been matched to this car's recorded defects yet. Reports are re-collected every quarter; the figures on this page do not depend on them.
Summaries written by us, never quotes; every entry links to its source. Owner reports have no denominator and never feed the failure rate.
SIMILAR CARS IN THE DATAclosest rate and age, other brands
Peugeot iOn18.7% fail · 343 testsTesla Model S18.0% fail · 10,892 testsCitroen C-Zero20.0% fail · 130 testsFord Mondeo12.2% fail · 370 tests
OTHER MERCEDES-BENZ ELECTRIC CARS
Three things the data shows
- 397 inspections in 2024 make this one of the adequately-documented electric cars in the data.
- Suspension take 1.9× the share of failures they take on petrol and diesel cars of the same age.
- Failure rate rises from 11.2% at 7 years to 17.4% at 8: a gentle ageing curve.
LIMITS // WHAT THE INSPECTION DOES NOT TELL YOU
No battery health, no motor, no charging performance. The test covers brakes, suspension, steering, tyres, lights, visibility and structure. A car with a badly degraded battery passes as long as it stops and steers. Read this page as evidence about the chassis, not the powertrain. Cars are tested from their third year, so the newest model years are missing; every figure carries its sample size for that reason. Full methodology.
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