The picture
B Series: a below-average pass rate worth digging into
Across 2,405 MOT tests, the B Series returns 66.3% first-time pass — well below the UK fleet average. The single most-logged Major fail is a split CV-joint boot. A torn suspension dust cover and windscreen damage round out the top three. Average tested mileage sits at 119,745, 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
188 occurrences · 7.8% of tests
- 02
A suspension joint dust cover severely deteriorated
178 occurrences · 7.4% of tests
- 03
Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view
148 occurrences · 6.2% of tests
- 04
Brake pipe damaged or excessively corroded
126 occurrences · 5.2% of tests
- 05
A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc
123 occurrences · 5.1% of tests
- 06
An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning
122 occurrences · 5.1% of tests
- 07
A rear registration plate lamp or light source missing or inoperative in the case of multiple lamps or light sources
113 occurrences · 4.7% of tests
- 08
The strength or continuity of the load bearing structure within 30cm of any sub-frame, spring or suspension component mounting (a 'prescribed area') is significantly reduced or inadequately repaired
91 occurrences · 3.8% of tests
- 09
A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning
91 occurrences · 3.8% of tests
- 10
Body, cab or chassis excessively corroded at a mounting point
85 occurrences · 3.5% 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
£120–£330
If every one of this B Series'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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Buying or keeping a B Series?
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 B Series 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.