From: peter@tsto.co.uk   
      
   On 13/11/2024 22:09, Snag wrote:   
      
   >    I thought it was exposure to sunlight/UV that caused most of the   
   > sidewall degradation ... or are those aftermarket tire covers (in   
   > particular for RV's and campers) just another scam ?   
   It's usually the UV which does the damage, though ozone cracking can   
   also occur. Mostly tyres rely only on the carbon black for UV protection   
   - I don't know of any other anti-UV additives which are widely used in   
   tyres. Better tyres may however contain (more or better) antiozonants   
   (yes, a real word, and thing).   
      
   I haven't come across aftermarket tire covers, but if a tyre is going to   
   be exposed outside for long periods, like RVs and campers, on a first   
   look just to prevent UV exposure they would make sense. They might also   
   slow exposure to ozone by providing a physical boundary, or be lined   
   with something which is more reactive with ozone than tyres - likely, as   
   ozone reacts with most plastics and fibers.   
      
   Tyres are made to last for 5 to 7 years, because on a normal car they   
   would need replacing due to wear after this time. However a RV or camper   
   might not need type replacement due to wear for decades, so protection   
   from UV and ozone could save a lot of money.   
      
      
   Whitewall tyres were originally made using zinc oxide as pigment, but   
   they use titanium dioxide nowadays. White rubber is more susceptible to   
   UV than black, because the lampblack or carbon black which makes tyres   
   black also helps protect the rubber against UV.   
      
   The carbon black does several other things. It decreases susceptibility   
   to attack by oxygen, increases the thermal conductivity - important to   
   prevent parts of the tyre from getting too hot -, strengthens the   
   vulcanisation, increases the tensile strength of the rubber, and   
   increases abrasion resistance. Whew, good stuff!   
      
      
   Peter Fairbrother   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)