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From: Peter Fairbrother <peter@tsto.co.uk>
Newsgroups: rec.crafts.metalworking
Subject: Re: 1991 ranger brake problem
Date: Fri, 15 Nov 2024 21:27:57 +0000
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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Whitewall tyres were originally made using zinc oxide as pigment, but 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