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 Post subject: NOS tyres
PostPosted: Thu Dec 20, 2018 3:04 am 
BoTM Winner / retrobike rider
BoTM Winner / retrobike rider

Joined: Tue Aug 11, 2015 4:58 pm
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Having recently seen some NOS tyres both in the FS section and elsewhere on the interweb for sale with descriptions such as "Still has factory wax coating" or "Still has white mould release agent" et cetera, that, I'm afraid to tell you, this is factually incorrect.

When a tyre is new, it won't have any coating or wax or dust or talc or anything on it. It's just bare rubber. Fresh as you like.

Over time - could be months, typically years - and depending on how it has been stored - sunlight is bad as it usually generates high levels of ozone in the local atmosphere around a tyre where it's kept - the tyre will 'age' and the protective waxes that are contained within the rubber compound* will migrate or 'bloom' to the surface (as well as other less visible chemical ingredients designed to protect the rubber's outer surface such as antioxidants and antiozonants). This blooming creates the white waxy layer you get over time. If you rub it it usually forms into crumbs, and you can wipe it away with your bare hands. Keep rubbing, more will be removed. Then, over more time, more will bloom out. Rub that off. And so on. Until there's not much left and the rubber dries, becomes brittle or eventually cracks or splits. Irreparable damage at this point.

The only way to revive tyres which have exhibited waxy bloom is to heat them, or post-cure, which will allow the wax to be reabsorbed into the compound.

Heat for about 30 minutes in an oven at 80°C (175°F).
This should see the wax reabsorbed.
Don't bake on heat above 100°C (212°F) for a prolonged time.
You'll also bake the sidewalls, typically made of a nylon fibre, which also dries out over time or when exposed to prolonged heat or sunlight.
SO take care.
You won't always know how a tyre has been stored, evening buying NOS in-the-box stocks, so some precautions must be taken.
In general, this is the method to use.

Finding an oven big enough for steel beaded tyres may prove a challenge, and post curing anything at home is to be exercised with the knowledge that rubber fumes will be generated so don't put the tyres in with your Sunday roast, and keep the room very well ventilated and use extractor of sorts if you have them. Don't breathe the fumes directly. Low exposure will not be harmful.

If successful, you can then prepare the tyre's surface with a sealant to protect future ageing or UV attack. I recommend an automotive tyre shine product. AutoGlym Instant Tire Dressing is ideal. Spray on over the tyre surface - taking care not to get on rim surfaces or brake rotors - wipe off excess, allow to dry, then buff. You're left with an invisible layer which seals and protects the tyre.

I have a pair of 1992 NOS Smoke and Dart that are a bit waxy so I'll do a post cure session myself to prove the concept, if anyone doubts the science. I have a but of experience in this field, and wouldn't dare mess about with dodgy advice on something of this importance.
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* A typical rubber compound will typically contain the raw synthetic rubber (polymer), a carbon black reinforcing additive in black tyres (silica in non-black tyres), process oils, chemical agents to promote the curing process (activators and accelerators), sulphur as the crosslinking agent, antioxidants and protective waxes. These are all mixed together in bulk using machinery to form a raw compound that is then 'cured' (or cooked, forming the chemical reactions to vulcanise/crosslink the rubber) in the tyre mould, after being laid up with the Nylon carcass, sidewall, tyre bead and liner. When cured, it should achieve 90 to 95% vulcanisation, leaving the remaining 5-10% to occur during its life, over time. Hence why a rubber hardens over time, because it is creating more crosslinks and becoming more plastic, less elastic, though not totally plastic by definition, even at 100% vulcanisation. This is why it is safe to post-cure at the above mentioned time and temperature to reabsorb those waxes.


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 Post subject: Re:
PostPosted: Thu Dec 20, 2018 6:26 am 
Retro Guru

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XLNT info ... thank you !!! :!:


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 Post subject: Re:
PostPosted: Thu Dec 20, 2018 7:44 pm 
retrobike rider
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Good point. Back in the 90's When I bought new tyres. Irc for example they were not white. Powderry and so on. Just stunk the whole shop out. 8)


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 Post subject: Re:
PostPosted: Thu Dec 20, 2018 8:37 pm 
PoTM Winner / retrobike rider
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That is, some really cool info, if only I had some tyres like that, that I wanted to restore as I could bosh them in one of the spray booths at work when we're baking a car!!

I used advice I'd heard before, about rejuvenating dried amber walls, by rubbing Vaseline into them, made them a little more supple and brought back the colour in the wall of the tyre quite well, as they were faded almost to white!

Oh and Marc, how dare you say that new tyres used to stink the shop out, I always loved that new tyre smell when I went into my lbs, that and gt85 :) :)


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 Post subject: Re:
PostPosted: Wed Dec 26, 2018 8:24 pm 
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I wonder if this could be done using a heat gun or a hair dryer?
I'll give it a go and report back.


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 Post subject: Re: Re:
PostPosted: Wed Dec 26, 2018 8:50 pm 
BoTM Winner / retrobike rider
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incorrigible wrote:
I wonder if this could be done using a heat gun or a hair dryer?
I'll give it a go and report back.

No, because you’ll only get localised heat from a gun or dryer, which will certainly exceed the temperature you’re aiming for as a post-cure. Same principle to being unable to bake a pie using a hairdryer. :|


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 Post subject: Re: Re:
PostPosted: Wed Dec 26, 2018 10:00 pm 
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regan_ev wrote:
incorrigible wrote:
I wonder if this could be done using a heat gun or a hair dryer?
I'll give it a go and report back.

No, because you’ll only get localised heat from a gun or dryer, which will certainly exceed the temperature you’re aiming for as a post-cure. Same principle to being unable to bake a pie using a hairdryer. :|
Got it, thanks.

I don't think I could easily fit a 26-inch tire into the oven in my kitchen, nor do I even want to fill the house with the smell of burnt rubber, so I suspect that it's just a matter of time before I get arrested for breaking into a pizza restaurant and using their stone oven to preserve some tires for a NOS build. :facepalm: I'll have to wear my RB hat for the mugshot.


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 Post subject: Re:
PostPosted: Wed Dec 26, 2018 10:08 pm 
Ain't no party like an S Club party
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I thought buyers paid extra for the white 'release mould' on NOS tyres?

Bugger, more money wasted pointlessly on bags of flour and talc.


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 Post subject: Re: Re:
PostPosted: Thu Dec 27, 2018 2:29 pm 
BoTM Winner / retrobike rider
BoTM Winner / retrobike rider

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BoyBurning wrote:
I thought buyers paid extra for the white 'release mould' on NOS tyres?

Bugger, more money wasted pointlessly on bags of flour and talc.

LOL
“Factory mould release” exists only in a selection of NOS tyres, it seems :roll: :lol:


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 Post subject: Re: NOS tyres
PostPosted: Thu Dec 27, 2018 2:35 pm 
BoTM Winner
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interesting


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