I have noticed from looking at various tyre sidewall markings (yes I know i need to get out more) that the ply construction on many of the budget brands consists usually of just steel and polyester. Virtually all of the premium brands however contain an extra nylon ply. On enquiring about this, a tyre fitter friend of mine told me that this nylon ply acts like a cap, that shrinks over the other belts as the tyre warms up. This is supposed to help prevent tread delamination at high speed. There is no legal requirement for manufacturers to fit this nylon ply.
My question to the BR is, in the "real world" of every day motoring does this really matter, or are an unsuspecting public being sold tyres that are missing a key safety feature?
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Know of any tyres that have suffered this delamination?
No, nor me and I am involved in motor sport too.
Known of a few blow outs especially on motorway (usually good "quality brand" tyres too) but mostly from sidewall damage or lack of tread.
There is an almost "we must hate cheap tyres" section around though.
What about other cheap stuff from the far east? Is that automatically dangerous too?
Would prefer to buy genuine uk (esp local) products but it gets harder!
Edited by yorkiebar on 26/01/2008 at 21:50
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Been searching for this link for ages. Only just found it again.
www.cbc.ca/consumers/market/files/cars/dangerousti...l
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Went out to check mine earlier (far eastern brand) No nylon plys listed on the sidewall. Should I be worried? I dont think so.
Edited by scaniadriver on 22/03/2008 at 21:08
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Craneboy, thanks for that very interesting cbc link.
My wife had a catastrophic tread separation whilst driving at 85mph (in the Middle East). Due to her skill, the stability of the Grand Cherokee and plenty of luck she was able to control the car to the hard shoulder. In all my 25 years of motoring on 4 continents (and motorsport on 3) I had never seen anything like it. And I hope never to see it again. (Picture link in my profile).
The tyre was a US-made Cooper Discoverer (as mentioned in the cbc report).
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Would prefer to buy genuine uk (esp local) products but it gets harder!
what like rover?
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You can knock rover (knock Honda at the same time maybe?) but they were much better cars (the later models) than were given credit for.
But name UK tyres, or other parts if you want ?? Not as easy as it sounds!
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But name UK tyres or other parts if you want ?? Not as easy as it sounds!
I think Dunlops are all made in Germany now (not necessarily a bad thing)
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>>a tyre fitter friend of mine told me that this nylon ply acts like a cap, that shrinks over the other belts as the tyre warms up
I don't think that the co-efficient of thermal expansion of nylon actually supports this view.
approximate values are;
Nylon has a CTE of about 100E-6 / K
Polyester, 100 to 120E-6 / K
Steel, 20E-6 / K
In my experience, most delaminations are caused by overheating, which in itself is generally caused by running the tyre too fast at too low air pressure - the excessive deflection results in energy being wasted via the rubber's hysteresis, and hence heating the tyre, and destroying the bond between carcass and tread capping.
As a bit of fun, I once ran a car on 5 psi for half a mile at 30 mph - afterwards, the tyre was too hot for me to touch. Don't worry - the tyre was scapped imediately afterwards! (actually, the car followed soon after!)
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NC, you're right, but in my wife's case, I am certain that, during our ownership, the tyre pressures were always correct +/- 10%.* However, the car and the tyres were second-hand so I cannot vouch for the previous owner. Also the car was used by us for off-roading in the desert. Plus I believe that exposure to sunlight also played a factor. All this combined with less-than-perfect manufacture = serious problems.
(* I had one of my pressure gauges properly calibrated at the certified calibration dept. at work).
As you say, tyres can get very hot indeed. I have driven Land Rovers for days at 15 psi on desert trips and scalded my hands changing punctures with gloves on. Then driven back to Uk at 80+ mph - no delaminations (luckily)! I have seen punctured tyres smoking when removed (due to heat build up when driven flat). (I have also driven a Range Rover down a motorway at 40mph on 3 tyres and a one steel rim when I forgot to pack the jack for a national rally - but that's another story!)
And surely all those huge payouts in the US mean some tyres have been proven to be defective.
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Don't worry - the tyre was scapped imediately afterwards! >>
Probably ended up being sold on as a decent part worn.. :-p
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Decent part worns and second hand tyres always come in for criticism too. probably rightly so, but...............
If you buy a 2nd hand car do you immediatley change the tyres? if not you are running about on tyres with unknown history!
The most important thing about tyres is to regularly check and inspect them? far more important than fit and forget imo!
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>If you buy a 2nd hand car do you immediatley change the tyres?
This is exactly what I will do!
After my wife's experience I changed all tyres on our two cars that we had bought 2nd hand. This was in the Middle East though where the problem for tyres is the 300 days of hot sunshine per year.
The tyres on the Clio were 5 or 6 years old factory fit Michelins and, whilst they still had at least half their tread left, they were very noticably losing their grip. The car had only done 20,000 miles.
Here is an interesting article on the dangers of buying part worn tyres:
www.tyresafe.org/data/files/Auto%20Express_18%20Ju...f
I have bought part worns once; 20 years ago, a couple of nearly new Michelins from a supplier in Manchester. I was able to select them and inspect them and they were fine. It was for my Spitfire and the tyres were the least of my worries.
Edited by Billy Whizz on 23/03/2008 at 12:15
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Skim read all the article, but 1 interesting point is that it recommends budget tyres for people on low budgets (a point I dont disagree with) rather than 2nd hand tyres.
Does that mean when purchasing a 2nd hand car (as per the example they highlighted) it would be recommended to put new budget tyres on (if better brands cant be afforded?) rather than run on the unknown tyres? So. if so, it could be an example of throwing away good (tread wise) named tyres and replacing with lesser brand names?
If the report is taken at its facevlaue (with all its comments) then that can be logically concluded! Not correct imo though!
Tyres are so emotive they do bring out some deep entrenched views dont they!
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