Model Reports 4 min read Updated 18 Oct 2026

MG ZS 2021: reliability & common MOT faults

In 2025, 86 in every 100 first MOTs on a 2021 MG ZS were passes. Most common reason for a fail: Tyre condition (front).

Summary

A 2021 MG ZS passed first time about 3 in every 100 more often than the average of the 2020 and 2022 model years.

At a glance

How 14,459 first tests went in 2025.

Passed first time
86 in every 100
Did not pass first time
14 in every 1001,956 failed first-attempt tests
The typical car
4 yearsabout 29,392 miles
First tests counted
14,459

What failed most often

  1. Tyre condition (front)14 in every 100 failed tests
  2. Tyre tread depth (front)10 in every 100 failed tests
  3. Brake pads (front)10 in every 100 failed tests

How we count this. Data: UK MOT open data, 2025. Only Class 4 cars on their first MOT of the year are counted. A car that fails and is fixed at the test station still counts as a fail in the first-attempt rate. These are raw results, not adjusted for age, mileage, or peer mix. The MOT does not test engine or gearbox internals.

Note:

These are patterns across 2021 MG ZS vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. A wear pattern follows age and use more than the way the car was built. They come from MOT defect codes, not manufacturer bulletins, recalls or a diagnosis of any one car.

Suspension

Three faults. The strongest is the wheel bearings (front): 24 times as often as on similar cars.

Figures below are measured across the 1,954 of 1,956 failed first attempts (99.9%) that recorded an odometer reading in 2025. Mileage is needed to compare like with like.

We only list faults with at least 20 failures and a rate of about 2.0 times that of similar cars, which keeps one-off results out of the list.

Wheel bearings (front)

Failed on 60 first tests24 times as often as similar carsLikely evidence

What it means

Excessive play in a wheel bearing, or a bearing that is excessively rough, is Major. Play so excessive that the bearing is likely to break up or directional control is impaired is Dangerous, and so is a bearing so rough that it is likely to overheat or break up.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 22 first tests, 19 times as often as on similar cars.

Coil spring (rear)

Failed on 98 first tests9.2 times as often as similar carsLikely evidence

What it means

A missing bump stop rubber is not a reason to fail a coil spring. When the vehicle is jacked and lowered, a spring that does not correctly locate as the suspension returns to its normal running position is rejected as insecurely attached. A missing spring is Major, and graded Dangerous where directional control is affected.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 26 first tests, 30 times as often as on similar cars.

Suspension arm ball joint (front)

Failed on 66 first tests3.7 times as often as similar carsLikely evidence

What it means

A suspension arm ball joint is failed under the general suspension pin, bush or joint wording. Excessively worn is Major, and likely to become detached is graded Dangerous.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 44 first tests, 3.4 times as often as on similar cars.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage. Advisories count notes recorded on failed first tests only.

Brakes

Two faults and one wear pattern. The strongest is the brake discs (rear): 5.2 times as often as on similar cars.

Brake discs (rear)

Failed on 145 first tests5.2 times as often as similar carsWear pattern

What it means

A brake disc or drum must be significantly worn before it is rejected, and being worn below the manufacturer's recommended limits is not a reason in itself. Significantly and obviously worn is Major, as is contamination with oil or grease. A disc or drum that is fractured, insecure, seriously weakened or missing is graded Dangerous.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 434 first tests, 3.3 times as often as on similar cars.

Brake performance (roller test, rear)

Failed on 88 first tests4.8 times as often as similar carsLikely evidence

What it means

A wheel with no recorded braking effort on the roller test is graded Dangerous. Inadequate effort, a brake grabbing severely, abnormal lag and excessive fluctuation in effort are each Major. So is significant brake effort recorded with no brake applied, which indicates a binding brake.

Also noted as an advisory

Testers also noted it as an advisory, worn but not yet failing, on 71 first tests, 5.0 times as often as on similar cars.

Handbrake efficiency below minimum (roller test)

Failed on 47 first tests2.7 times as often as similar carsPossible evidence

What it means

A parking brake with efficiency below the minimum requirement is Major, and graded Dangerous where efficiency is less than half of the required value. On a roller brake tester, the requirement counts as met if more than half of the wheels of a brake system lock. The check applies only to vehicles whose parking brake was not already tested as the secondary brake.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage. Advisories count notes recorded on failed first tests only.

Lamps and electrical

One fault: headlight (front), 3.6 times as often as on similar cars.

Headlight (front)

Failed on 87 first tests3.6 times as often as similar carsLikely evidence

What it means

On vehicles first used on or after a set date, a halogen headlamp unit converted to take HID or LED bulbs fails for light source and lamp not compatible, which is Major. A complete unit built with those light sources is not failed for that. The precise position of the lamps is not part of the inspection beyond a visual look to see that they sit at about the same height and distance from each side.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Advisories

Other things testers noted as worn or close to failing, more often than on similar cars.

An advisory is a note from the tester about something that has not failed yet. It is an early warning, not a fail. Advisories for the faults above are shown with those faults.

Engine oil leaks

Noted on 25 first tests2.0 times as often as similar carsElevated evidence

Data: UK MOT open data, 2025. Counts cover advisories recorded on failed first tests only, compared with cars of the same age and mileage.

MOT pass rates

How first tests ended, and how the pass rates are counted.

Passed first time
86in every 100
Passed on the first test.
Fixed at the station
3in every 100
Failed, then fixed at the test station the same day.
Failed
11in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 86.5% of 14,459 first tests (2025): only cars that passed first time count. Official-style pass 88.9%: cars fixed at the test station also count as a pass. The 3 fixed and the 11 not fixed make the 14 in every 100 that did not pass first time.

By fuel type

First testsTypical mileagePassed first time, as testedPassed first time, same mileage
Petrol9,45029,455 miles8787
Electric5,00829,186 miles8585

Figures are in every 100 first tests. Cars with more miles usually fail more often, so the same-mileage figure gives every fuel the mileage mix of all the cars in this year.

Same model, other years

Passed first time in every 100, all tested in 2025.

406080100201720182019202020212022Older carsNewer cars
406080100201720182019202020212022Older cars

Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 88 in every 100 passed first time.

YearPassed first timeFirst tests
201766 in every 100333
201874 in every 1004,845
201975 in every 1008,181
202081 in every 10011,763
2021 This car86 in every 10014,459
202285 in every 10017,287

If you are buying one

What this year's MOT record means for the decision in front of you.

Mileage matters most on a 2021 MG ZS.

Of 2021 MG ZS vehicles with under 20,000 miles, 92 in every 100 passed their 2025 MOT first time. With 41,000 miles or more, 79 in every 100 did.

Under 20,0003,079 tests
92
20,000–26,0002,555 tests
90
26,000–33,000 Typical car3,149 tests
86
33,000–41,0002,646 tests
85
41,000 and over3,027 tests
79

What to check at your mileage

How often each fault turned up on a failed first test, by the car's mileage. Read it as: what is likely to need looking at on a car like the one in front of you.

Under 20,00026,000–33,00041,000 and over
Tyre condition (front)0.71.93.6
Tyre tread depth (front)0.11.42.7
Brake pads (front)0.22.11.6
Brake discs (rear)0.60.81.7
Coil spring (rear)0.40.51.4

Faults per 100 first tests, by the car's mileage at the test.

When a car fails

58in every 100

of failed cars had one item to fix.

16in every 100

of failed cars had three or more items to fix.

4in every 100

of all first tests had a defect the tester marked dangerous (unsafe to drive away).

Every figure here is a first-attempt MOT rate from DVSA open data for this model line, for cars of this model year tested in 2025. Each mileage band holds a fifth of the tests. MOTs do not test engine or gearbox internals, so this is a pre-purchase checklist, not a full reliability score.

FAQs

Short answers about how to read this model-year guide.

A 2021 MG ZS passed first time about 3 in every 100 more often than the average of the 2020 and 2022 model years. In 2025, 86.5% of 14,459 first MOTs on the 2021 MG ZS passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 88.9%. Among 1,956 failed first-attempt MOT tests (test year 2025), Wheel bearings (front) appears more often than on similar cars (3.1% of those tests; 60 observed failures; about 24× more often than similar cars). There is no single reliability score here; this is a pre-purchase checklist built from DVSA open data, not a guarantee for any individual car.
Ranked by how often they were actually recorded, the items that most often failed a 2021 MG ZS at the first attempt were Tyre condition (front) (14.1%), Tyre tread depth (front) (9.8%) and Brake pads (front) (9.7%), each as a share of the year's failed first attempts. That is what goes wrong most often on the car. The common faults table shows a different measure: faults that are unusual compared with similar cars.
Among failed first-attempt tests we highlight patterns that appear more often than on similar cars. Top example: Wheel bearings (front) (3.1% of those tests; 60 observed failures; about 24× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Wheel bearings (front) shows up more often than on similar cars (3.1% of those tests; 60 observed failures; about 24× more often than similar cars). That does not prove a design fault. Age, mileage, and how the car was used still matter. Treat it as a pre-purchase checkpoint, not a manufacturer service bulletin.
Common MOT problem areas for the 2021 MG ZS include Wheel bearings (front), Coil spring (rear), Brake performance (roller test, rear). These are the faults that stand out compared with similar cars, not a complete list of what can go wrong on any individual car.
Advisories flag issues noted at the test and are not a fail rate. We show advisory patterns that appear more often than on similar cars among failed first-attempt tests, separate from common failure rows. Use them as early-warning checks, not as a pass/fail score.
This page highlights MOT failure patterns for the 2021 MG ZS (registration year) using UK DVSA open data for the selected test year. Patterns are compared with cars of a similar age and mileage. It is a buyer checklist from MOT defect statistics, not a full service history or manufacturer service-bulletin list.
No. MOT tests do not cover engine internals, gearboxes, or many electronic modules. Patterns here come from MOT defect statistics only and should not be read as engine or gearbox reliability scores.

About this data

How this page is built and what it can (and can't) say.

These figures come from UK MOT open data for this model year. We surface common failure patterns against similar cars, not a full reliability score, and not a pass/fail verdict on any individual vehicle.

2024 2025

What we include

UK Class 4 cars only. Normal MOT tests (not retests); first test per vehicle per calendar year; results pass, PRS, or fail.

Same-day repairs

PRS means the car failed items that were fixed at the test station and then passed the same day. We count PRS as a first-attempt fail in headline rates so same-day repairs do not hide problems.

How we compare

We compare this model year with other Class 4 cars of similar age and mileage in the same test year. This model family is left out of the peer group so the car is not measured against itself.

What this does not cover

  • MOTs do not cover engine internals, gearboxes, or many electronics; this is not a full reliability score.
  • Common faults come from MOT defect stats, not manufacturer TSBs or recalls.
  • Age and mileage matching reduces, but does not remove, differences in how cars were used and maintained.
  • If the data for a car is too thin to say anything useful, we say so rather than guess.

Contains public sector information licensed under the Open Government Licence v3.0.

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