Check Your Car's Suspension Before MOT

The MOT test is a crucial annual check to ensure your vehicle is safe and roadworthy. While many people focus on brakes and lights, the suspension system often gets overlooked. However, a faulty suspension can lead to an MOT failure, not to mention compromising your car's handling and safety. Fortunately, there are several straightforward checks you can perform at home to identify potential issues before your official test. This guide will walk you through the process of assessing your car's suspension, helping you understand common problems and how to spot them.

Understanding Your Car's Suspension System

Before diving into the checks, it's helpful to have a basic understanding of what your car's suspension system does. Its primary roles are to maximise the friction between the tyres and the road surface, provide steering stability with respect to the road, and ensure passenger comfort by isolating the cabin from road noise, bumps, and vibrations. Key components include shock absorbers (or dampers), springs, struts, ball joints, control arms, and anti-roll bars. Any wear or damage to these parts can significantly impact your car's performance and safety.

The Bounce Test: A Quick Indicator

One of the simplest and most effective ways to get a preliminary idea of your shock absorber condition is the 'bounce test'.

1. Ensure your car is on a level surface.
2. Go to one corner of the car and firmly push down on the wing (the metal panel above the wheel).
3. Release the pressure quickly.
4. The car should settle back to its normal position. If it bounces up and down more than once or twice, the shock absorber on that corner may be worn.

Repeat this test for each corner of the car. While not a definitive diagnosis, a noticeable difference in bouncing between corners can indicate a problem. This test is particularly useful for identifying worn shock absorbers, which are a common cause of MOT failure.

Visual Inspection: What to Look For

A thorough visual inspection is essential. You'll need to get under your car (safely, using axle stands if you're lifting it) or look closely at the wheels and suspension components. Here's what to examine:

Shock Absorbers and Struts

Look for any signs of oil leaks on the body of the shock absorber or strut. A greasy or oily film is a strong indicator that the seals have failed and the damper is leaking. Leaking shock absorbers are illegal and will cause an MOT failure. Also, check for any physical damage such as dents or corrosion on the casing.

Springs

Inspect the coil springs for any signs of cracking, corrosion, or sagging. Broken springs are a definite MOT failure. Significant corrosion can weaken the spring, making it prone to breaking. A spring that has lost its tension (sagged) will alter the car's ride height and affect its handling.

Bushings

Suspension bushings are typically made of rubber or polyurethane and are used to isolate vibration and allow for controlled movement in suspension joints. Check these for signs of cracking, tearing, or perishing. Worn bushings can lead to excessive play in the suspension, affecting steering and alignment, and are a common reason for an MOT failure.

Ball Joints and Tie Rod Ends

These are critical steering and suspension components. With the wheel jacked up and the engine off, try to move the wheel from side to side (at the 3 o'clock and 9 o'clock positions). Any significant play or knocking sound could indicate worn ball joints or tie rod ends. This is a crucial safety check, as worn components can lead to loss of steering control. Excessive play here is a major MOT concern.

Control Arms and Links

Examine the control arms and any associated links for damage, bending, or corrosion. Check the points where they attach to the car's chassis and the suspension components for worn bushings or signs of stress.

Anti-Roll Bars (Sway Bars)

The anti-roll bar helps reduce body roll during cornering. Check its mounting points and links for wear or damage. Worn anti-roll bar drop links are a frequent MOT failure point.

Checking for Uneven Tyre Wear

Your car's suspension, if misaligned or worn, can cause uneven tyre wear. Look at your tyres:

• Feathering: Where the edges of the tread blocks are worn smooth on one edge and sharp on the other. This often indicates alignment issues.
• Edge Wear: If the inner or outer edge of the tyre is significantly more worn than the rest of the tread, it could point to suspension geometry problems or worn ball joints.
• Centre Wear: Usually indicates over-inflation, but can sometimes be related to suspension.
• Patchy Wear: Uneven wear in patches across the tread can be a sign of worn shock absorbers.

Significant or unusual tyre wear is a strong indicator of underlying suspension or steering problems and will be scrutinised during an MOT. Ensuring your tyres are in good condition and evenly worn is a good proxy for a healthy suspension.

Listen for Noises

Pay attention to any unusual noises your car makes, especially when driving over bumps or turning. Clunking, knocking, or creaking sounds from the suspension can indicate worn components, such as bushings, ball joints, or even damaged springs. A persistent knocking when going over bumps is a classic sign of suspension trouble.

Ride Height and Handling

Has your car started to sit lower than it used to, particularly on one side? This could be a sign of sagging or broken springs. How does your car handle? If you notice excessive body roll when cornering, the car feels unstable, or it pulls to one side, these are all potential symptoms of suspension issues. A car that feels 'floaty' or wallows after going over bumps may have ineffective shock absorbers.

Simulating MOT Checks

While you can't replicate the precise methods of an MOT tester, you can simulate some of their checks:

Wheel Wobble Test

With the car securely jacked up, grip the wheel at the 3 o'clock and 9 o'clock positions and try to rock it back and forth. Any play or looseness suggests worn wheel bearings or steering components, which are often linked to suspension integrity.

Spring Compression Test

An MOT tester will often check the condition of the spring itself. While you can't easily compress it, you can look for obvious damage as mentioned earlier.

Damper Check

Beyond the bounce test and visual inspection for leaks, an MOT tester will assess the damping effect by physically pushing down on the car and observing how quickly it returns. You can do this too, as described in the bounce test.

Common Suspension Failures in MOTs

Here's a quick summary of the most common suspension-related reasons for MOT failure:

When to Seek Professional Help

If you're unsure about any of these checks, or if you find any of the issues mentioned, it's always best to consult a qualified mechanic. They have the tools, experience, and knowledge to accurately diagnose and repair suspension problems. Ignoring suspension issues can not only lead to an MOT failure but also compromise your safety and the safety of others on the road. It's also worth noting that some suspension components are quite complex and may require specialised tools or knowledge to replace correctly.

Conclusion

A proactive approach to checking your car's suspension can save you time, money, and potential hassle with your MOT. By performing these simple visual and physical checks, you can identify common problems early and address them before they become major issues. Remember, a well-maintained suspension is vital for your car's handling, safety, and longevity. Don't let worn suspension components be the reason you fail your MOT – a little preventative maintenance goes a long way.