Re: Tyres
Posted: Wed Jul 07, 2010 9:09 pm
This assertion that tyre strength becomes unsafe after 6 years isn't supported by the chemistry of the materials in tyres at all - it sounds very much like total bullshit promulgated by tyre manufacturers to sell more tyres.............
Let's look at the materials commonly used in tyres, and their age-related degradation characteristics:
The carcass is a rubber compound, that will suffer from oxidation and UV degradation with age. However, this degradation usually happens from the outside inwards, so is easy to spot from a good visual inspection. Its also very dependent on the actual formulation of the compound, so life will vary massively both with exposure conditions and compound.
Next, let's look at the internal tyre structure. There will be steel wires, either just as bead reinforcement or embedded in the carcass to stabilise the tread section under load. Provided that the steel remains embedded in the rubber compound and isn't exposed to the air, then its calendar life will be very long, certainly many tens of years. If the carcass uses steel tread and sidewall reinforcement then it may fatigue with use, but this is likely to be well in excess of the rubber compound normal wear limit.
The tyre may use synthetic fibres, such as nylon, polyester or even Kevlar as internal reinforcement. These can degrade with UV exposure and heat, but have a very, very long calendar life if protected from UV exposure and excessive heat. Inside a tyre carcass their calendar life would be close to infinite.
If tyres are protected from sunlight, kept properly inflated and, perhaps, lifted off the ground when not in use for long periods, then they will easily last for ten to twenty years or more. There are reasonably high numbers of veteran and vintage cars running around quite safely on tyres that are much, much older than this.
Jeremy
Let's look at the materials commonly used in tyres, and their age-related degradation characteristics:
The carcass is a rubber compound, that will suffer from oxidation and UV degradation with age. However, this degradation usually happens from the outside inwards, so is easy to spot from a good visual inspection. Its also very dependent on the actual formulation of the compound, so life will vary massively both with exposure conditions and compound.
Next, let's look at the internal tyre structure. There will be steel wires, either just as bead reinforcement or embedded in the carcass to stabilise the tread section under load. Provided that the steel remains embedded in the rubber compound and isn't exposed to the air, then its calendar life will be very long, certainly many tens of years. If the carcass uses steel tread and sidewall reinforcement then it may fatigue with use, but this is likely to be well in excess of the rubber compound normal wear limit.
The tyre may use synthetic fibres, such as nylon, polyester or even Kevlar as internal reinforcement. These can degrade with UV exposure and heat, but have a very, very long calendar life if protected from UV exposure and excessive heat. Inside a tyre carcass their calendar life would be close to infinite.
If tyres are protected from sunlight, kept properly inflated and, perhaps, lifted off the ground when not in use for long periods, then they will easily last for ten to twenty years or more. There are reasonably high numbers of veteran and vintage cars running around quite safely on tyres that are much, much older than this.
Jeremy