Tires: Tire Safety, internal combustion engines, nylon cap

Question
Barry:

There is a self-proclaimed tire expert http://ncrs.org/forum/tech.cgi on this discussion board.  I think he has a degree in Internal Combustion engines.  Certainly no dummy.  He tends to have a chicken little(the sky is falling) tendency when answering questions about which tire to use on a vintage Corvette.

Anyway, he insists on recommending I think it is an "s" speed rating.  Whatever 140 mph is.  He goes on to say that these are the only tires that have some type of nylon cap over the steel radial belt and keeps the tire from disintegreting in case of structural failure of the tire.  Anything less than this, according to him is taking your life and your precious car in your own hands.  Tires (again, according to him) that are not speed rated or have the minimum DOT rating are designed to withstand only 85mph at maximum load and max inflation pressure.  Another statement is that there is no 70 or 78 profile tire that is safe to use on the highway because of the design of the tires.  

When it was pointed out that 85 mph was ten miles an hour over the speed limits of most states and could even land you in jail under certain conditions and also that 99% of Vintage Corvette owners (say '53-'67 models) only drive maybe a thousand miles a year and at relatively slow speeds, it did not alter his position one bit.

I think this guy's opinion is in outer space.  Would you care to comment on the general safety of OEM design tires as verified by your experience in the business and through your testing procedures.

Could you also draw a safety comparison between OEM four ply nylon made in the '50's-'60's, the bias belted in the '70's and today's OEM radials?

Thanks,
Mike  

Answer
Mike,

Lots to cover and only so much space.

I've read a bunch of his comments, and I hate to say it, but I share his opinion, with a couple of exceptions.  He may be overstating it somewhat, but it got you thinking and asking questions, didn't it.  That's a good thing.

First, IMHO, Corvettes are performance cars and they deserve performance tires.  In my book that means H rated tires minimum.

I realize that in days of old, bias ply tires were what was available, but since we got 'em, we should use 'em.

I disagree about the nylon overlay being the cure for tire failures.  However, tires with nylon overlays (H rated constructions) have higher capabilities, ergo, they should fail less often.

But there is one thing I feel obligated to point out and I hope you'll pass this on to the group.

The latest research I have seen seems to indicate that tire perfomance deterioration is time dependent (age) and not so much dependent on usage (wear or mileage) or exposure to ozone.  I have a problem with that, but data is data.  However, I do agree that older tires should not be used.

I am currently recommending that tires be replaced when they reach 10 years from the date of manufacture, regardless of how much they have (or have not) been used.  In AZ, CA, NM, TX, NV, and FL, I recommend 6 years of age.  Other states would be proportionally in between.  For example, NC would be 8 years.  It's an ambient temperature relation.

BTW, I'll grant an exception for a trailer queen.  But the queen is not allowed to dance - not without her sneakers!

Now the issue of repo tires being equal to the OEM tires:

On the one hand, rubber chemistry has improved over time, as has the processing equipment.  However, the folks building these repo tires aren't at the forefront of technology, particularly advances in quality and non-destructive testing techniques.  I have some real reservations about making a statement that repo tires are equal to the OEM quality of the day, and I am very confident they are nowhere near the quality of tires produced today.

This is not to dis the folks who make and sell these tires.  It's just that they are filling a niche and doing a good job at it.

Are they adequate?  Different question - they probably are.

One last word - "safety".  I prefer to think of it as risk.

Taking a vehicle out on the road has a certain amount of risk associated with it.  Increase the speed and the risk goes up.  Our concept of what is risky today would be laughed at in the 60's and 70's, but I think we are smarter and more knowledgeable now.  We should do what we can to be less risky, acknowledging that risk is part of life and sometimes the experience is worth the risk.

Hope this helps.