My 67 Vette has tires that were installed in the mid to late 80's, but only maybe 1000 miles ago. Tread is fine as you can imagine, but there are small cracks showing up in the sidewall (only on the outside and not on the inside sidewall facing the car interestingly enough). They are Michelin XH tires. I don't drive the car much, but want to feel confident that they can still be driven on safely (at even slower speeds). How much cracking can I consider normal?
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Re: Tire age, cracking, safety, etc.
Tough call! How much sun and ozone have they seen in the fifteen years they've been installed. The outside cracks could be from UV. Does the car spend a lot of time outside?
Small cracks as you report are generally not dangerous as long as the tire holds air (no more than 1-2 psi monthly loss).
Duke -
Re: Tire age, cracking, safety, etc.
Thanks Duke. There is probably some UV, but really not very much. Car has been garaged the whole time, but dirt, grime, etc. was allowed to build up as the car was not in a driving condition for several years. When I was cleaning the tires up, I noticed the cracking.Comment
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I have the same thing except...
I have white - lettered Goodyear GT's that are around 18 years old, and have discovered "cracking" only on the frame side of the tire. My Goodyear dealer said this was age induced dry rot, and ultimately the sidewall would weaken to the point where bulging would occur. He did say if they were his that he would use them for "awhile" while keeping an eye out for problems, but avoiding high speed driving would probably be wise. For me, new tires are in order when I have finished my restoration, properly broken-in the engine, generally debugged the car, and ready for some "high speed driving". IMHO - what's another few hundred bucks on top of all the time and money spent already to be road worthy?Comment
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Re: Tire age, cracking, safety, etc.
Duke,
I plan to participate in the national road tour this year (as I did last year) with my 66 coupe and will be driving a total of approximately 1,500 mlies round trip between New York City and Windsor, Canada. I have BF Goodrich radial TA's on the car which are about 12 years old with about 5,000 miles on them. The car is always garaged so the tires have not been exposed to much sunlight and contimue to look good with no visible defects. Given the age of the tires and the type of highway driving I will be doing on the road tour, should I be concerned with the integrity of the tires?Comment
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Re: Tire age, cracking, safety, etc.
No, I don't think you need to be concerned, however, since those tires probably carry only an "S" speed rating I would recommend fairly high pressure - 34/32 for your big block, or 32/32 if you had a small block.
One reason why I always recommend higher speed rated tires, even if you don't plan on driving that fast, is that they they constructed with better materials that will not degrade with heat as rapidly as lower speed rated tires.
In any event, as I pointed out in my tire article in The Corvette Restorer, most "correct" modern radial replacement sizes have total load capacity nearly double the Corvette's gross weight, so the fairly light load they carry implies additional safety margin.
DukeComment
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Re: Tire age, cracking, safety, etc.
I would be VERY leary of any radial tire with the carcass over 5 years old. In my former life I was in vehicle maintenance for a 2,000+ vehicle fleet. We saw a dramatic increase in tire problems in tires over 5 years old. A lot of tread separations.
On my car trailer, I blew three Michelins in short order. Manufacture dates placed tires about 60 mos old.
For a few bucks it ain't worth the safety risk, or the hassle of repairing or replacing a fender because the tire blew. Radial treads usually come off in one LARGE piece.Dick WhittingtonComment
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Re: Tire age, cracking, safety, etc.
Catastrophic tread separations on radials with nylon cap belts are rare. That's why I keep harping on "high speed rated tires" even if you don't "plan on driving at 150 MPH". Typically, any tire with an "H" or above speed rating will have a nylon cap belt and a UTQG temperature rating of "A".
I've experienced three tread separations on race tracks, but in every case the tire did not disintegrate. They developed big bulges in the tread, and the vibration gave me ample warning that there was a problem, but in every case the tire remained intact and held air. I even drove the 75 miles home from Riverside on one because I had already used my spare.
If you buy the highest quality tires and keep them away from the sun and ozone they will last almost indefinitely. If you buy cheap tires with a speed rating below "H", a UTQG temperature rating of less than "A", and no nylon cap belt, you are probably going to have a tire problems before the tread is down to the wear bars. For a few bucks it isn't worth the risk to buy a set of cheap tires instead of a set of much higher quality high speed rated tires.
DukeComment
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