It's a frustrating scenario many car owners in Peterborough have experienced: you bring your vehicle in for its MOT test, only to be handed a failure certificate and a list of repairs needed. Failing an MOT means time off the road, unexpected expenses, and the hassle of scheduling a retest. The good news is that most MOT failures happen for a handful of very common (and often preventable) reasons. By knowing what these common failure points are, you can take steps to avoid them before your test – saving yourself both money and stress.
Every year, the DVSA (Driver and Vehicle Standards Agency) publishes data on why cars fail their MOT test. And year after year, the same issues tend to top the charts. In our own experience at Peterborough MOT Station, we see the same patterns: whether it's a family car in Hampton, a work van in Werrington, or a commuter vehicle regularly driving down the A1, the reasons for MOT failure are usually quite similar. However, Peterborough's mix of city driving and rural roads can put particular strain on certain parts of your car. For example, frequent short trips in town can affect your emissions system, while bumpy country lanes might wear out suspension components faster.
In this article, we'll break down the top reasons vehicles fail MOTs and give practical tips on how to avoid each one. Think of it as a checklist of trouble spots. If you address these proactively – a bit of DIY checking or a quick visit to a mechanic – you stand a much better chance of passing your MOT in Peterborough the first time around. Let's get into it.
The problem: Faulty lights are consistently the number one cause of MOT failures across the UK. This includes headlights, tail lights, brake lights, indicator (signal) lights, reverse lights, and even the tiny number plate bulb. All these lamps are essential for safety, especially during dark winter evenings or foggy mornings in Peterborough. If any required light isn't working, or if a bulb is the wrong colour (e.g., an indicator bulb faded from orange to white), it's an MOT fail. Headlights can also fail for incorrect beam aim – if they're pointing too high and could dazzle other drivers, or too low such that you don't see far enough.
Why it happens: Bulbs can blow at any time, and many drivers don't notice immediately (it's hard to tell if your own brake light is out, for example, unless someone informs you or you check reflections). Also, with the salted roads in winter and general grime, lens covers can get cloudy or dirty, affecting light output. Bumpy roads or speed bumps, of which Peterborough has plenty in residential areas, can sometimes jolt bulbs and shorten their lifespan.
How to avoid it: Do a thorough light check a day or two before your MOT. Grab a friend or family member to walk around the car while you test all lights, or park near a reflective surface. Check:
Replace any bulbs that are out. They're usually inexpensive (a few pounds at most) and available at auto parts stores or even supermarkets. Ensure the bulb you install is the correct type and fitting. Also clean your light lenses; a wipe with a soft cloth can ensure they're not obscured by dirt. For headlight beam aim, if you haven't adjusted anything it should be fine, but if you often carry heavy loads in the boot, remember to reset your headlight leveling dial when you're not loaded. If you're unsure about beam alignment, many garages will check and adjust headlight aim for you quickly.
Local tip: With Peterborough's winter being quite dark and damp, you rely on your lights a lot. Driving on the unlit rural roads around the outskirts (like the route to Thorney or Newborough at night) with a headlight out is not just an MOT issue, it's dangerous. So staying on top of your car's bulbs helps you stay safe year-round, and it certainly means a smoother MOT inspection.
The problem: The second most common MOT failure reason is tyre issues. This could be tyres that don't meet the legal tread depth (minimum 1.6mm), or tyres that are damaged (cuts, bulges, or cords exposed). Also, mismatched tyres on the same axle or serious cracking due to age can cause fails. In short, if your tyres aren't safe, your car won't pass the MOT.
Why it happens: Tyres wear out gradually, and many drivers let them run too low on tread without realising it. In a place like Peterborough, you might have lots of stop-start driving which wears the front tyres faster, or you may frequently drive on the A47 or other fast roads which can cause different wear patterns. Potholes – particularly after winter or on smaller country lanes around Cambridgeshire – can cause sidewall bulges or bent wheel rims that lead to slow punctures or uneven tyre wear. If you've ever bumped up a kerb while parking in town or hit a notorious pothole on Lincoln Road, it's worth checking your tyres afterwards.
How to avoid it: Regularly inspect your tyres, at least once a month or before long journeys. Use the 20p coin test for tread depth: insert a 20p into the tread grooves; if you can see the coin's outer band, your tread might be under 1.6mm. Ideally, don't wait that long – many experts suggest changing tyres at ~3mm for optimal wet grip. Check across the width, as inner or outer edges can wear out of sight (especially if your wheel alignment is off).
Look for signs of damage: cuts or gouges in the rubber, nails or screws stuck in the tread, bulges in the sidewall (which indicate internal damage). If you see any cords or fabric, that's a serious fail and the tyre is unsafe to drive on. Also ensure your tyres are the right type and size for your vehicle; usually they will be, unless someone accidentally fitted an odd one.
Keep your tyres inflated to the correct pressure as per your car's handbook. Underinflated tyres wear faster on the edges and overinflated ones wear in the center, plus both conditions reduce grip. The cold mornings in Peterborough can drop tyre pressures slightly, so check them when the tyres are cold at a petrol station or with a home gauge. Proper inflation also helps with fuel economy (a bonus given fuel prices!).
Finally, remember the spare if you have one: while a spare tyre itself isn't part of the MOT, if it's flat or visibly damaged and you have it in use, that could become an issue. Generally, make sure any tyre on the car meets the standards.
By taking care of your tyres, you not only avoid MOT trouble but also improve your safety. Good tread is your best friend in heavy rain on the parkways or when navigating slushy winter roads in Peterborough.
The problem: Issues with the braking system are another top reason for MOT failures. This can manifest as worn out brake pads or discs, brakes not providing enough stopping force on the test machine, or imbalanced braking between wheels. A very common failure (and one we've seen a lot in Peterborough) is the parking brake (handbrake) not having enough hold. If the testing equipment shows that your handbrake cannot hold the car securely, it's a fail. Leaking brake fluid or seized brake components will also cause fails.
Why it happens: Brakes naturally wear with use. Urban driving with lots of braking (for traffic lights, roundabouts, etc.) like we have in Peterborough city centre can wear pads and discs relatively quickly. If you mostly do motorway or parkway cruising, brakes might last longer, but eventually they all need replacing. The handbrake can go out of adjustment over time, or cables can stretch, especially if you regularly park on hills or rely on it heavily. Corrosion can affect brake lines or the parking brake mechanism, particularly with road salt in winter.
How to avoid it: Be attentive to your brakes in everyday driving. If you hear a screeching or scraping noise when you brake, that often means your brake pads are low (some pads have wear indicators that squeal). If braking feels less sharp than it used to, or you notice the pedal travel becoming longer or spongy, get your brakes checked well before the MOT. Sometimes you don't notice gradual degradation, so consider having your brake pads and fluid inspected at service intervals.
Before the MOT, test your handbrake: find a safe incline and see if a few clicks of the handbrake hold the car. If you have to pull it to the very top of its travel, it may need adjustment or new rear brake shoes/pads. Many modern cars have rear disc brakes with an integrated handbrake mechanism that can stick or weaken if not used often, so using your handbrake regularly helps keep it working properly.
Check your brake fluid level under the bonnet. If it's low, top it up with the correct spec fluid, but also investigate why it's low – brake pads worn or a leak possibly. Note that if you top it off and then later get new pads (which push the brake pistons back), the fluid might overflow, so don't overfill it.
Also consider brake balance: if your car pulls to one side when braking, you might have uneven braking due to a sticking caliper or uneven pad wear. This will show up on the MOT as an imbalance between left and right brakes. A garage can perform a brake test if you're unsure; it's better to fix it (often a simple service of the brakes) than to fail and have to do it anyway.
At Peterborough MOT Station, we've had customers fail on handbrake performance and be genuinely surprised, because they rarely use it (for instance, some drivers of automatics rely just on "Park"). So especially if you have an automatic car, remember to exercise that handbrake and ensure it stays effective.
The problem: The MOT test includes checking the condition of suspension components (shock absorbers, springs, arm bushings, ball joints, etc.) and steering linkages (track rod ends, steering rack, power steering system). Common failures in this category include broken road springs, leaking or ineffective shock absorbers, or excessive play in joints or bearings. If a coil spring is snapped (even just the end of it, which is common), that's an MOT fail. Likewise, a shock absorber leaking oil or not damping properly will fail. Worn ball joints or tie rod ends that allow too much movement (felt as "play" in the steering) also cause failure.
Why it happens: Simply put, Peterborough's changing road conditions can be tough on your car's suspension. Think about the countless speed humps in areas like Stanground or Hampton, or the rougher road surfaces on some rural routes around the fens. Every bump and pothole puts stress on springs and shocks. Over time, metal fatigues and can crack. Cold weather and salt can accelerate spring failures too (springs often break more in winter). High mileage or lots of driving on uneven roads will wear out suspension bushings and joints. Additionally, the general climate and road conditions in the UK mean rust can attack suspension components over the years.
How to avoid it: Some suspension issues give warning signs, while others might not be obvious until a mechanic raises the car. Here are a few tips:
Preventative maintenance for suspension is tricky – parts will wear out as part of normal use. But avoiding rough roads and potholes when you can, or slowing down for bumps, can prolong their life. Keeping tyres properly inflated also helps reduce undue strain on suspension. If you do hear or feel something off, getting it inspected sooner rather than later can save you from a more expensive repair if the part fully fails (for example, a worn ball joint could eventually snap, which is dangerous).
The problem: Another surprisingly common MOT failure comes down to how well you can see out of your car. This includes the condition of your windscreen wipers, the windscreen itself, and whether the washer jets work properly. If your wipers are worn and not clearing the screen effectively (leaving big streaks, or the rubber is split), that's a potential fail. If the windscreen has a significant crack or an untreated chip in the driver's line of sight, that can fail. And if the washers don't spray (maybe the pump is broken or simply out of fluid), that's a fail as well.
Why it happens: Wiper blades wear out with use and age. After months of wiping rain, frost, and grime, the edges get ragged and can tear. In Peterborough, where we do get plenty of rain and mist, wipers get a workout. People also often forget to refill washer fluid, or they only add water which can freeze or clog the system. As for windscreens, it's common to get a stone chip at some point – perhaps on the A1 at speed, or a loose bit of gravel on a country lane. If ignored, that tiny chip can spread into a larger crack when the glass contracts in cold weather or if the car goes over a bump.
How to avoid it:
Also, ensure your mirrors are intact and adjusted. A missing or cracked driver’s side mirror is a fail. The passenger side is needed unless the interior mirror gives a full rear view. So if you've been driving around with a cracked mirror glass (maybe from a little parking scrape), get that fixed.
Having clear visibility is obviously critical when driving down the parkway in heavy rain or merging onto a busy roundabout like the one near Eye. By replacing wipers and repairing any windscreen damage ahead of time, you remove another big reason cars fail MOTs.
The problem: Vehicles can fail the MOT on emissions if they are producing too much pollution (measured via the exhaust gases), or if the exhaust system has issues like leaks, excessive noise, or missing components (for example, a removed catalytic converter or diesel particulate filter will fail). Common issues include high CO or hydrocarbon levels for petrol engines (which could signal incomplete combustion or a failing catalytic converter), or visible smoke from diesels (black smoke can indicate excessive soot, blue smoke oil burning, etc.). A loud, blowing exhaust from a hole or crack can also cause a fail, since it can affect emissions readings and obviously isn't in proper working order.
Why it happens: Emissions can be high for various reasons. For petrol cars, lack of maintenance (old spark plugs, clogged air filter) can make the engine run rich or misfire. A faulty oxygen sensor or worn-out catalytic converter will also raise emission levels. For diesels, one major cause is a clogged DPF (diesel particulate filter) or EGR valve issues, often due to lots of short trips that never let the engine get hot enough to burn off soot. (A Peterborough driver who mainly does short city hops might see this; diesels need a good run occasionally to clear out the DPF.) Also, mechanical issues like a worn turbo can cause smoke. As for the exhaust hardware, rust is the typical culprit. We get plenty of moisture and salt on the roads in winter, which eats away at exhaust pipes and mufflers over time.
How to avoid it:
In Peterborough, we might not have mountainous terrain, but we do have lots of traffic at times – and an idling car in traffic that is well-maintained will pollute less and smell less bad than one that's belching unburnt fuel or diesel smoke. Keeping your car's emissions clean is good for everyone, and it avoids that MOT failure sheet.
The problem: Beyond the big categories above, there are a few other issues that commonly cause MOT fails:
Why it happens: Most of these are due to wear and tear or minor neglect. Seatbelts get yanked and over many years can fray. People sometimes ignore a broken latch or interior door handle, but it becomes an issue at MOT time. Rust can creep up on older cars, especially if they’ve seen a lot of wet and salt. As for plates, some people like decorative plates or have old ones; if they aren't to spec, an MOT is when you'll get caught.
How to avoid it:
Most newer cars (say under 10-15 years old) won't have too much trouble with structural rust yet, but things like seatbelts and door handles can affect any car if broken. It's mostly about checking the basic functions that we sometimes overlook.
Knowledge is power when it comes to MOTs. If you know what testers are looking for – especially the top failure items – you can take action beforehand. Most of the issues above (lights, tyres, wipers, etc.) can be checked by any car owner with a bit of time and minimal tools. Fixing them is often quick and cheap, which is far cheaper than a re-test fee or driving around with a car that's technically illegal because it has no valid MOT. In other words, tackling car repairs before MOT day (rather than scrambling after a failure) saves you time, money, and hassle.
If you’re not confident checking these yourself or you want professional help, many garages (including us at Peterborough MOT Station) offer a pre-MOT check or will happily take a look if you mention you're concerned about something. Sometimes just getting a regular service before the MOT can catch a lot of these items, since mechanics will often replace worn wipers or bulbs and advise on tyres during a service.
Remember, an MOT isn't the same as a full service. It’s possible to pass an MOT with an advisories list of things that are borderline. Those advisories are hints of what to keep an eye on. For example, you might pass but get "tyre close to legal limit" noted – take that as your cue to budget for new tyres soon rather than wait till it's a definite fail. Keeping on top of maintenance year-round means you won't have a mad scramble before test day.
Finally, if your vehicle does fail, don't be too hard on yourself. The whole point of the MOT is to catch issues that you might not have noticed. Once fixed, you'll have the peace of mind that your car is safer for you and other road users. And you’ll be back on the road around Peterborough, hopefully not seeing the garage again for another year (except for friendly visits)!
To make booking your MOT in Peterborough easier and get more tips on keeping your car in top shape, visit our MOT service page. We’re always happy to help local drivers understand why regular MOT testing and maintenance is so important. By avoiding these common pitfalls, you can keep your car running smoothly and ensure the MOT is a straightforward affair each year.
