Passenger vehicles should not be fitted with re-treaded tyres. This is the word from tyre maker Bridgestone which said that while retreads are often used on heavy vehicles, they are not suited to the operating conditions of passenger vehicles.
“Passenger cars are expected to provide good roadholding and braking, and provide safety and comfort when travelling at freeway speeds,” explained Bridgestone PR Manager, Desirée van Niekerk. “Retreaded tyres are not suitable for fitment on modern passenger vehicles.”
Retreaded tyres are tyres where the tread of the original tyre has reached the end of its service life and has been replaced with a procured thread. This process involves scrubbing away any remaining tread and bonding a new tread area to the tyre. A similar process, called re-grooving, is used in tyres which have been designed with extra tread base into which new tread can be cut once the original has worn out. The National Road Traffic Act, 1996 (Act No.093 of 1996) states that “1) No person shall operate on a public road-(I) a motor vehicle which is equipped with a regrooved tyre having a bead diameter of 430 millimetres or less.”
However, re-grooving is highly dangerous when it is carried out on tyres which were not designed to be re-grooved, including passenger tyres. Re-grooving and re-treading are fleet management strategies which are typically used to increase the service life of tyres fitted to heavy vehicles. These tyres are not required to be able to withstand the high speeds and dynamic loads imposed on passenger car tyres.
Nonetheless, even in heavy vehicle applications, it is good practice to never fit retreads to the steering axle (front wheels) of a vehicle. “The steering axle is a critical axle where tyre failure is potentially deadly,” explained van Niekerk. “A properly-made retread on a heavy vehicle tyre is extremely reliable in practice, but one always wants the peace of mind of a new tyre on the front axle.”
Fleet tyre management strategies frequently use the newest tyres on the front wheels, with older tyres fitted further back on the vehicle. For instance, the drive wheels of a mechanical
horse would be good candidates to fit with retreads if the fleet owner has chosen not to opt for a custom drive tyre like Bridgestone’s R-Drive. Tyres further back on the combination, such as on a semi-trailer, may be retreaded tyres.
“A heavy vehicle tyre’s carcass eventually reaches the end of its life and can no longer be retreaded,” commented van Niekerk. “But passenger tyres carcasses are not designed to travel several hundred thousand kilometres. Even an initial re-treading comes with an increased risk of tyre failure. A retreaded tyre also cannot be guaranteed to comply with the speed and load rating of the original tyre.”
Bridgestone said the most effective way to reduce tyre costs over the lifetime of a passenger car is to ensure that tyres are always correctly inflated to provide the most economical operation. Correct driving style also helps prolong tyre life, such as avoiding harsh braking, heavy cornering and sudden acceleration.
“Good driving and tyre maintenance habits can increase tyre life by up to 30% and in many cases, this can offset the cheaper cost of retreads,” van Niekerk commented. “But safety remains the top issue. Retreaded tyres are a good choice for heavy vehicles, but not for passenger cars,” she concluded.