Tyres & the tyre bay 44 November 2026 ǁǁǁ͘ ĂŌĞƌŵĂƌŬĞƚŽŶůŝŶĞ͘ ŶĞƚ Beyond balancing: Tracking down tyre-related vibration When conventional wheel balancing fails to resolve a vibration complaint, technicians need to look beyond the obvious. Bridgestone technical manager Peter Moulding explains how tyre uniformity, flat spotting and irregular wear can help identify the underlying cause. Vibration complaints can be challenging for technicians, particularly when a wheel balance has been checked and no obvious fault has been identified. However, a correctly balanced wheel and tyre assembly can still generate vibration, making it important to consider other factors when investigating noise, vibration and harshness (NVH). According to Peter Moulding, Technical Manager at Bridgestone, tyre uniformity, flat spotting and irregular wear are all worth considering when conventional balancing fails to resolve the problem. Understanding tyre uniformity One of the most significant contributors to tyre-related vibration is uniformity, particularly first harmonic variation. First harmonic refers to the once-perrevolution element of tyre uniformity. In simple terms, it describes how consistently the tyre maintains its shape as it rotates. A tyre that is slightly out of round, for example, may behave more like an egg than a perfect circle, creating a repetitive disturbance with every revolution. This becomes particularly noticeable when the frequency of the disturbance coincides with the natural frequency of the vehicle, amplifying the vibration felt by the driver. Another important measurement is the peak-to-peak value, which represents the difference between the highest and lowest points around the tyre. This is the second most important value in tyre uniformity, after the first harmonic component. For technicians, the distinction is important: balancing addresses the distribution of mass around the wheel assembly, whereas uniformity concerns the consistency of the tyre’s shape. A wheel can therefore be correctly balanced yet still produce an unwanted vibration. Recognising flat spotting Flat spotting can develop in different circumstances, and understanding the vehicle’s recent history can help identify the likely cause. Heavy braking can create a localised flat spot, resulting in a repetitive bouncing sensation as the affected section of the tyre contacts the road. The disturbance can also contribute to further flat spotting around the tyre. Flat spotting can also occur when a vehicle remains stationary for an extended period. Motorhomes and motorcycles, for example, may develop temporary flat spots after being stored over winter. In these cases, the tyre may temporarily lose its normal shape where it has been in contact with the ground. Careful driving until the tyre warms up should allow it to regain its normal shape. Consequently, technicians investigating a vibration following prolonged storage should consider whether the symptoms change as the tyres warm up. However, persistent vibration should not automatically be attributed to temporary flat spotting; further inspection may be necessary to establish the cause. What irregular wear reveals Tread wear patterns can provide further clues when diagnosing a difficult NVH complaint. Diagonal wear is one example highlighted by Bridgestone. This can result from mismatched tyres being paired together, causing one tyre to skip rather than roll consistently. Worn or damaged suspension components can also contribute to the problem. This makes a thorough tread inspection an important part of the diagnostic process. Technicians should look for diagonal wear patterns and compare the condition of the tyres across the vehicle, rather than concentrating solely on the wheel assembly identified as the source of the vibration. Where irregular wear is present, checking the condition of the suspension is particularly important. Replacing a tyre without addressing an underlying mechanical fault could allow the problem to recur. Identifying the source When balancing and visual inspection fail to provide an answer, specialist
RkJQdWJsaXNoZXIy MjQ0NzM=