Why is wheel balancing not required for rear wheels?

[VanIsabela]

If the rear wheels have neither been replaced nor had tire repairs, meaning their mass remains unchanged, then wheel balancing is unnecessary. However, replacing or repairing rear wheels alters their mass distribution, making balancing essential. Generally, wheel balancing is required whenever any part of a tire's mass is modified. Tires have a limited lifespan, typically around 5 years. As rubber products, they gradually harden and age over time, leading to cracking under pressure, reduced load-bearing capacity, and increased susceptibility to blowouts. Even within normal service life, tires must be replaced once their tread wear reaches the raised indicators in the tread grooves.