The picture
R-Class: middle-of-the-pack on first-time pass
Across 2,952 MOT tests, the R-Class returns 74.0% first-time pass — below the UK fleet average. The single most-logged Major fail is a split CV-joint boot. A missing CV-joint boot and windscreen damage round out the top three. Average tested mileage sits at 119,558, which is the lens to read those failure rankings through. If you own one and the next test is close, the ranked list below is a sensible pre-test checklist.
Top ten reasons for rejection.
- 01
A transmission shaft constant velocity joint boot severely deteriorated
381 occurrences · 12.9% of tests
- 02
A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc
111 occurrences · 3.8% of tests
- 03
Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view
103 occurrences · 3.5% of tests
- 04
Brake pipe damaged or excessively corroded
84 occurrences · 2.8% of tests
- 05
A rear registration plate lamp or light source missing or inoperative in the case of multiple lamps or light sources
69 occurrences · 2.3% of tests
- 06
A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning
69 occurrences · 2.3% of tests
- 07
Parking brake efficiency below minimum requirement
57 occurrences · 1.9% of tests
- 08
Tyre tread depth not in accordance with the requirements
54 occurrences · 1.8% of tests
- 09
A shock absorber damaged to the extent that it does not function or showing signs of severe leakage
47 occurrences · 1.6% of tests
- 10
A tyre cords visible or damaged
39 occurrences · 1.3% of tests
Counts cover Major and Dangerous defects logged at test. Advisory items excluded so this shows why a car was rejected, not just what the tester flagged in passing.
Worst-case fix budget · top 2 failures
£48–£125
If every one of this R Class's most-logged Major fails hit at the same MOT, that's the real-world UK garage range. Reality is usually one or two items, not all of them. Open the estimator →
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Tools that pre-empt a retest.
Picked against this car's top failure patterns. Affiliate links to Amazon UK — we earn a small cut at no cost to you. Disclosed up-front, doesn't shape the data.
Buying or keeping a R Class?
Use the failure ranking as a pre-test checklist or a haggling lever. Treat the headline pass rate as a fleet-wide trend, not a guarantee on any individual car.
If you own a R Class and your last MOT looked nothing like the ranked failures above, that's normal — individual cars vary widely. The ranking shows the patterns testers flag most often across the country.