Mercedes-Benz B-Class: what fails at MOT
106,000 MOT tests on the Mercedes-Benz B-Class in 2024, counted. 25.4% failed at the first attempt.
The short answer
25.4% of Mercedes-Benz B-Class tests failed at the first attempt. Cars of the same ages averaged 27.4%, so the B-Class is about average for its age.
It fails most often on lights and electrics (6.6% of tests), suspension (5.7% of tests) and tyres (4.6% of tests).
By year of registration
Older cars fail more, whatever the model. So each year is shown beside the figure for all cars first used that year.
| First used | Tests | Failed first time | All cars that year | Typical mileage |
|---|---|---|---|---|
| 2021 | 3,305 | 7.8% | 10.9% | 19,700 13,300 to 28,000 |
| 2020 | 4,862 | 7.3% | 11.5% | 23,200 15,300 to 32,100 |
| 2019 | 6,833 | 9.8% | 13.4% | 27,600 18,700 to 37,400 |
| 2018 | 5,836 | 12.4% | 15.6% | 35,500 25,200 to 48,400 |
| 2017 | 8,441 | 15.7% | 18.2% | 44,800 32,000 to 59,600 |
| 2016 | 8,118 | 18.3% | 21.3% | 50,600 36,200 to 68,200 |
| 2015 | 8,312 | 20.4% | 24.4% | 60,000 43,700 to 78,200 |
| 2014 | 12,445 | 23.9% | 27.7% | 68,600 51,200 to 87,700 |
| 2013 | 10,283 | 26.5% | 30.6% | 74,100 55,000 to 96,000 |
| 2012 | 8,469 | 27.7% | 33.4% | 79,800 58,600 to 100,900 |
| 2011 | 4,820 | 40.6% | 36.1% | 81,500 63,100 to 101,200 |
| 2010 | 6,217 | 41.2% | 38.6% | 87,000 67,400 to 107,700 |
| 2009 | 5,879 | 42.7% | 39.8% | 92,200 72,500 to 113,700 |
| 2008 | 4,886 | 44.3% | 41.5% | 98,400 77,100 to 120,600 |
| 2007 | 3,721 | 43.8% | 41.5% | 101,300 77,100 to 123,200 |
| 2006 | 3,031 | 44.2% | 42.4% | 99,600 79,100 to 122,900 |
| 2005 | 586 | 44.5% | 42.2% | 103,800 82,400 to 133,200 |
Green is at least three points better than other cars that year, red at least three points worse. Typical mileage is the middle reading at the test, with the range the middle half of cars fell in.
Where it fails
The share of Mercedes-Benz B-Class tests with at least one failure in each part of the MOT, beside what cars of the same ages average.
| Part of the test | B-Class | Cars its age |
|---|---|---|
| Lights and electrics | 6.6% | 7.5% |
| Suspension | 5.7% | 6.2% |
| Tyres | 4.6% | 4.3% |
| Brakes | 4.0% | 4.5% |
| Wipers, washers and windscreen | 2.6% | 3.0% |
| Exhaust and emissions | 2.0% | 2.1% |
| Body and structure | 2.0% | 2.2% |
| Seat belts and airbags | 0.9% | 0.6% |
The parts that fail most
- Tyre3.8%
- Coil spring2.1%
- Headlamp aim1.8%
- Washers1.7%
- Engine warning light1.6%
- Ball joint1.4%
- Number plate light1.4%
- Driveshaft joint1.4%
- Linkage ball joint dust cover1.4%
- Brake pads1.3%
Share of tests with a failure on that part.
The most common failures
- Coil spring: fractured or broken2.1%
- Engine warning light: inoperative or indicates a malfunction1.6%
- Linkage ball joint dust cover: ball joint dust cover no longer prevents the ingress of dirt1.4%
- Ball joint: excessively worn1.4%
- Driveshaft joint: constant velocity boot split or insecure, no longer prevents the ingress of dirt1.3%
- Tyre: has a cut in excess of the requirements deep enough to reach the ply or cords1.3%
- Number plate light: inoperative in the case of a single lamp or all lamps1.3%
- Brake pads: less than 1.5 mm thick1.1%
- Washers: provides insufficient washer liquid1.1%
- Tyre: has ply or cords exposed1.0%
What testers warn about
Advisories are things that passed this time but are wearing. They are the best guide to next year's bills.
- Tyre tread: worn close to legal limit/worn on edge10.7%
- Tyre: slightly damaged/cracking or perishing6.7%
- Brake discs: worn, pitted or scored, but not seriously weakened5.4%
- Brake pads: wearing thin5.0%
- Brake pipes: corroded, covered in grease or other material4.9%
- Brake discs: worn, but not excessively2.3%
- Ball joint: has slight play1.7%
- Coil spring: corroded1.7%
What these figures can't tell you
An MOT is a safety and emissions test. These figures show how often the model fails that test. They say nothing about engines, gearboxes or electronics that break between tests, and how a car has been looked after matters more than its badge. The car you are looking at has its own MOT record, and that is the one to read.
Ask before you travel
- “Do all the lights work, including the number plate lights and brake lights?”
- “Have any suspension parts been replaced, such as springs, ball joints or bushes, and can I see the invoice?”
- “How much tread is left on each tyre, and how old are they?”
- “When were the brake pads and discs last changed?”
Check a Mercedes-Benz B-Class's own MOT record
Looking at a B-Class? Type its registration to see every test that car has had, what it failed on and what it was warned about, free.
Where this comes from
DVSA anonymised MOT tests and results, 2024, published by the Driver and Vehicle Standards Agency. Contains public sector information licensed under the Open Government Licence v3.0. The counting is Hindsight's own.
First-attempt MOT tests of cars first used 2004 to 2021. A test counts as failed if it failed or only passed after a repair during the test. Retests are left out. Built on 13 November 2026.