11/08/2016
Alloy wheels are a prominent feature on most modern vehicles, enhancing both aesthetics and performance. However, like any component subject to the rigours of the road, they are susceptible to damage. One of the most concerning forms of damage is a crack, which not only compromises the integrity of the wheel but also poses significant safety risks. For any driver in the UK, understanding the implications of a cracked alloy wheel, particularly concerning the annual MOT test, is absolutely crucial. A seemingly minor crack can lead to serious consequences, from a slow puncture to a catastrophic wheel failure whilst driving, and it will almost certainly result in an MOT test failure.
Understanding Cracked Alloy Wheels
Alloy wheels, while robust, are unfortunately prone to cracking, especially when subjected to sudden, forceful impacts. This vulnerability is often more pronounced in larger, higher-end vehicles such as BMW, Jaguar, Land Rover, and Mercedes. The primary reason for this increased susceptibility in such vehicles is often their larger wheel diameters, which typically mean a reduced tyre sidewall. This thinner layer of rubber offers less cushioning and protection for the alloy wheel against the notorious hazards of British roads, such as deep potholes and unforgiving kerbs.
What Causes an Alloy Wheel to Crack?
The most common culprits behind a cracked alloy wheel are direct impacts with road imperfections. A run-in with a sharp-edged pothole or an accidental scrape against a kerb can impart sufficient force to cause a crack. It’s a common misconception that such damage only occurs at high speeds; sadly, even low-speed impacts can be enough to compromise the wheel's structure.
From a professional's perspective, two main types of cracks are frequently encountered:
- Short Crack: This type of crack typically extends only down the outer rim or the bead sealing area of the wheel. These cracks can often be subtle and may even be visible from underneath the car while the wheel is still fitted, making them discoverable during routine inspections or an MOT test.
- Long Crack: A more severe form, a long crack, will have not only split the outer bead but also begun to creep into the inner wheel rim. This indicates a more significant structural compromise.
Both types of cracks share a common symptom: they will invariably lead to a slow puncture, causing a gradual loss of tyre air pressure. Many drivers only become aware of a cracked wheel when they take their vehicle in for a new tyre fitting, and the mechanic spots the damage. Regardless of its size or location on the rim, any crack in the wheel rim is a critical issue that demands immediate attention.
The Dangers of Driving with a Cracked Alloy Wheel
Driving with a cracked alloy wheel is highly dangerous and not recommended under any circumstances. The problems associated with a cracked wheel manifest almost immediately and can escalate rapidly:
- Loss of Tyre Air Pressure: As mentioned, a crack acts as an escape route for air, leading to a slow, persistent leak. This results in underinflated tyres, which are less efficient and compromise handling.
- Poor Handling and Steering Issues: An underinflated or structurally compromised tyre/wheel combination can severely affect the vehicle's stability and responsiveness. This can make the car feel 'wobbly' or unpredictable, especially when cornering or braking.
- Difficulty Balancing the Wheel: A cracked wheel loses its structural integrity, making it impossible to balance correctly. An unbalanced wheel leads to vibrations, accelerated tyre wear, and increased strain on suspension components.
- Risk of Catastrophic Failure: The most alarming danger is the potential for the crack to worsen while driving, potentially leading to a sudden and complete wheel failure or a tyre blowout. This could result in a loss of control, putting the driver, passengers, and other road users at severe risk.
If you notice that you are frequently needing to top up your tyre pressure, or if your vehicle's handling feels off, a cracked or buckled alloy wheel should be among the first things you investigate.
Cracked Alloy Wheels and the MOT Test
One of the most pressing questions for any driver with a damaged wheel is: Is a cracked alloy an MOT failure? The unequivocal answer is yes. A cracked alloy wheel is considered a dangerous defect and will result in an immediate MOT failure.
MOT Testing Standards: What the DVLA Says
According to Section 5.2.2 of the revised MOT Testing standards for Class 3-7 vehicles (which includes most cars and light commercial vehicles), a fractured wheel rim is explicitly listed as a dangerous defect. This means that if an MOT tester identifies any fracture or welding defects on a wheel during the inspection, they are obligated to issue a fail certificate. The structural integrity of the wheel is paramount for vehicle safety, and any compromise is taken very seriously.
It's also important to be aware of other wheel-related defects that can lead to an MOT failure:
- Dangerous Defects (MOT Fail):
- Any fracture or welding defects on a wheel.
- A tyre retaining ring likely to come off.
- A wheel distorted or worn to the extent the wheel or tyre is likely to become detached.
- Major Defects (MOT Fail):
- A tyre retaining ring not correctly fitted.
- A wheel badly distorted or wear between wheel and hub at spigot mounting.
- A wheel and its fittings not compatible.
While a welded alloy wheel itself will not fail an MOT test, it will only pass if the repair is deemed adequate. An inadequate repair, where the weld is poor quality or the structural integrity has not been fully restored, will still lead to a failure.
Repairing a Cracked Alloy Wheel
The good news is that in most cases, cracked alloy wheels can be successfully repaired. This highly specialised service requires specific tools, skills, and expertise. Professionals typically utilise the TIG (Tungsten Inert Gas) welding process, which provides a strong, durable, and precise repair.
The Alloy Wheel Repair Process
Repairing a cracked alloy wheel is a meticulous process that involves several critical steps to ensure the wheel's safety and longevity:
- Wheel Removal: The wheel is first safely removed from the vehicle.
- Leak Check: A thorough leak check is performed to identify all points of air loss, confirming the presence and extent of the crack(s).
- Tyre Removal and Inspection: The tyre is carefully removed from the wheel, and its condition is checked for any secondary damage that might have occurred due to the cracked rim.
- General Wheel Inspection: The bare wheel is then placed onto a balancing machine for a comprehensive check-over. This step helps identify not only the crack but also any accompanying buckles, as cracks and buckles unfortunately often occur together from the same impact.
- Crack Preparation: The area around the crack is meticulously cleaned, and the crack itself is gently cut open. This crucial step ensures that the weld material can fully penetrate and fill the crack, creating a strong, cohesive bond.
- Drilling the Weld End: A small hole is drilled at the very end of the crack. This technique helps to dissipate flex and diffusion, preventing the crack from propagating further after the weld has been applied. It's a key step in ensuring the long-term durability of the repair.
- TIG Weld Repair: The crack is then expertly welded using a TIG welding plant. This process involves using a non-consumable tungsten electrode to create an arc, which melts the parent material and a filler rod, fusing the crack together.
- Grinding and Finishing: Once the weld is complete and has cooled, it is carefully ground back to the original contour of the inner weld and the tyre seating bead. This ensures a smooth finish and, critically, that the tyre can seat correctly and safely.
Only in cases where the wheel is extensively damaged, for example, multiple severe cracks, or a crack that compromises the central hub, might a repair be declined. It's always best to have a wheel expert assess the damage.
Cost of Repairing a Cracked Rim
The cost of repairing a cracked alloy wheel is typically structured simply, reflecting the labour, expertise, and specialised equipment involved. For most standard crack repairs, you might expect a cost around £81.95 + VAT. A typical breakdown includes:
| Service | Cost (Excluding VAT) |
|---|---|
| Crack repair | £57.95 |
| Additional crack (if present) | £28.95 |
| Remove & refit wheel and tyre | £24.00 |
Buckled Alloy Wheels and MOT Implications
While the focus has been on cracks, another common form of wheel damage is buckling. A buckled wheel occurs when the wheel's rim is bent out of shape, preventing it from aligning correctly with the tyre. Like cracks, buckles are usually caused by impacts with poor road surfaces, potholes, or high kerbs.
Can You Drive on a Buckled Alloy?
No, it is not safe to drive on a buckled alloy wheel, even if the bend appears slight. Driving on a buckled wheel can:
- Cause damage to your vehicle's steering and handling components.
- Lead to uneven tyre wear.
- Increase the risk of flat tyres or, more dangerously, a tyre blowout.
It's imperative to address a buckled wheel as soon as possible to prevent further damage and ensure safety.
Is a Damaged Alloy an MOT Failure?
Yes, a badly damaged, distorted, cracked, or scratched alloy wheel can indeed cause your vehicle to fail its MOT. The MOT tester will likely determine that the structural integrity of the alloy has been compromised, falling under the same dangerous or major defect categories as a cracked wheel.
Repairing a Buckled Alloy Wheel
Slightly buckled alloy wheels can often be repaired. This process typically involves using specialist hydraulic equipment to carefully press the buckles out of the alloy, restoring its original shape. Not all garages offer this service, as it requires specific machinery and expertise. The cost for a buckled wheel repair can start from as little as £60 per wheel, depending on the severity of the buckle and any additional damage.
Frequently Asked Questions
Here are some of the most commonly asked questions regarding cracked and damaged alloy wheels:
Do alloy wheels crack easily?
Alloy wheels can be prone to cracking, particularly when they encounter hard objects like potholes or kerbs. Vehicles with larger wheels and lower-profile tyres are often more susceptible due to less protective rubber.
What happens if you have a cracked alloy?
A cracked alloy wheel will immediately cause problems such as a loss of tyre air pressure, poor handling, and difficulty balancing the wheel. It's a dangerous issue as the crack can worsen, leading to further deterioration and potential failure whilst driving.
Will a cracked rim leak air?
Yes, a cracked rim will almost certainly leak air, causing the tyre to lose pressure. This leads to underinflation, poor handling, and increased tyre wear. If you find yourself regularly topping up your tyre pressure, a crack or buckle could be the cause.
Can you drive with a cracked alloy?
It is strongly advised not to drive with a cracked alloy wheel. The crack can worsen significantly while driving, leading to a dangerous situation, including potential wheel failure or a tyre blowout. Furthermore, a cracked alloy wheel is an MOT failure.
Is a cracked alloy an MOT failure?
Yes, absolutely. According to Section 5.2.2 of the revised MOT Testing standards for Class 3-7 vehicles, a fractured wheel rim is classified as a dangerous defect, meaning it will result in an immediate MOT failure.
Can a crack in an alloy wheel be repaired?
In most cases, yes, cracks in alloy wheels can be repaired using a specialised TIG welding process. However, severely damaged wheels might be deemed beyond safe repair by experts.
Is a damaged alloy an MOT failure?
Yes, any badly damaged, distorted, cracked, or severely scratched alloy that compromises the wheel's structural integrity will likely cause an MOT failure.
Is a welded alloy wheel an MOT failure?
No, a welded alloy wheel itself will not fail an MOT test, provided the repair is deemed adequate and structurally sound by the MOT tester. An inadequate or poor-quality repair, however, will result in a failure.
Will wheel rim damage be an MOT failure?
Yes, any significant damage to the wheel rim, such as fractures, distortion, or wear that compromises safety, is likely to be an MOT failure under Section 5.2.2 of the MOT testing standards.
Can a slightly buckled alloy wheel be repaired?
Yes, slightly buckled alloy wheels can often be repaired by professionals using specialist hydraulic equipment designed to press the buckles out, restoring the wheel's correct shape.
Conclusion
The integrity of your vehicle's wheels is fundamental to your safety and the performance of your car. A cracked or severely damaged alloy wheel is not just an aesthetic issue; it's a significant safety hazard and a guaranteed MOT failure. Regular inspection of your wheels for any signs of damage, such as cracks, buckles, or persistent air loss, is crucial. If you suspect or discover a cracked alloy wheel, it is imperative to seek professional assessment and repair immediately. Investing in a timely and professional repair not only ensures your vehicle remains roadworthy and passes its MOT but, most importantly, protects you and others on the road from potentially dangerous situations. Don't compromise on wheel safety; address any damage promptly.
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