I have an 87 Vert which I bought 4 years ago. All works exceptionally well but I have a concern with the Yokohama tires on it. They still have 50% tread left on them, but I believe they are about 7 - 10 years old. Even though they seem OK (they do ride rough as expected) and both my mechanic and tire guy say they are safe, I still have some doubts. Do you think they should be replaced and if so, any suggestion. This C4 is driven on weekends and is rarely driven hard. The 87's seem to have few choices compared to later C4's because of their 16 inch size.

Any advice would be appreciated.

 

My 86 came with four nice Michlens that were over six years old. This you can read off of the DOT number molded into the sidewall. The last three digits represent the year 199(9) and the week of the year (52) last week of December. I spoke to a Michlen rep who was very upfront and called headquarters for confirmation. He indicated that the Mfgr will "warranty" the tires for four years from the DOT number date. After that I'm on my own. We inspected the sidewalls and tread for weather checking and the like without finding any thing of concern.

So if I crash on a six year plus old tire in a high performance car like a Vette, I shouldn't plan on recovering damages from them. As a responsible driver, I should not be driving over the legal limit on these tires.

Anyways the rules for the closed course races in Nevada won't allow any tires beyond four years old max!. No exceptions. Sounds good to me!

 

They're probably safe, especially if your mechanic and tire guy say so.

However you are not going to give you very good grip or ride. Tire rubber gets hard with age.

If you enjoy the grip and ride well enough, then keep using them. But you'd probably enjoy the car more with newer tires. Newer tires will also have a lot better technology than 10 year old tires, so the grip and ride should be that much better.

If the size is hard to find, maybe it's time to upgrade to 17" wheels.

 

My Goodyears are 10 years old. With that being said, I read in Road & Track that tires are affected by Ozone and other chemicals in the air, and should be replaced every 7 years. I'd examine the rubber on the threads. Is it supple or brittle. Just like a drive belt.

 

Weather and ozone do cause problems for tires. Tires left outside to where the sun shines on them will in effect "dry out" and begin to deteriorte (ever see large RV's with covers over thir tires??). The chemicals that go into the tread compound begin to dry and the tire will effectively lose their gripping ability.

As the tire dires, there is a much greater chance of the sidewalls or tread cracking whic could lead to a failure of some sort.

The original GS-C's on my 92 pretty much lost any grip after 6 years and I wound up replacing them with a set of Bridgestone Potenza RE730's about 6 years ago. While I have done some track days and a couple season of autocross on these tires, I don't think I would do that now even though the tires look fine and there is still about 70% tread left.

As far as tire selections for 84-87 cars (and those 88's with the 16" wheel, go to the Tire Rack web page www.tirerack.com and on the main poage, click on Products/tires and in the page that opens, enter the size 255 50 16 to get a list of available tires. In the page that pops up, choose the top 3 boxes in both the Summer and All-Season categories to see a list that size by of manufacturers and models. There still is a decent selection to choose from for the early cars. Goodyear, Kuhmo and Dunlop are good brands and of these, there are still tires with speed ratings of W, Z, and Y

Don't use the H-rated tires unless you do not push the car hard at all, The early C4's are easily capable of faster speeds than the 130MPH H-rated tires.

 

Thank you for all of your advice. It is very appreciated. This forum has some very knowledgable Corvette owners who can always be counted on for assistance.

Best of luck as always.

 

My nearly 5yr old GY Eagles had age cracks for the last year or so and I took them through the traps many times at a little over 100mph but would not cruise on the highway for extended period up there.

Upon replacing them a few months ago with new GY Eagle Ultra HP Plus I indeed noticed enhanced grip and smoothness of ride. Since I've been reminded above of potential damage from sun and contaminents, I intend to be more meticulous with sidewall dressing care in the future.

Since your tires show no signs of severe deterioration they should be good to go for a few more years. If you want to enhance ride feel try the GY Eagles mentioned.

 

Based on what you said were your driving habits were I would look at Kumhos ASX. I just put them on mine replacing Firehawks. They are highly rated at Tirerack "W" rated to 148mph Tread Life rating of 400(= 4X the average) and are good in rain. The best benefit is price I got all 4 for my 93 shipped to my door for $500

 

i also drove on GSC's that were at the time 12 years old. daily driving was not terrible, even in rain and snow(!) but when i entered in the first autocross with the Corvette i skated around as if someone dumped oil on the track. i could not really tell if the tire was "hard" or "brittle" by just touching them - they looked fine but obviously were not. they could've even been dangerous in an emergency manouver.

i would also recommend Tire Rack for your new tires - since you are in PA you should get them a day or two after your order. the only catch is that you will need to know someone you trust to mount & balance your tires.

 

I am still riding on the Yokohama A403's that were on my 85 when I bought it 10 years ago and still have 1/4 tread left. I don't even know when Yoko stopped making them.

 

A ten year old tire will not fail due to age, but the grip they offer will be somewhat less than when they were new.
If you don't need maximum grip, they'll be fine and probably last another 10 years.(hard rubber doesn't wear as fast...)

Larry
code5coupe

 

baby it and they'll be fine.

the tires on the '48 Oldsmobile we have are probably 20 years old... but that car sees about 50 miles a year

 

That is incorrect. Tires do fail due to age, and at much less than 10 years.

I know at least some tire manufacturers recommend against using tires > 5 years old, and also some car owner's manuals have similar warnings.

In fact the NHTSA is thinking about requiring expiration dates on tires, and 5-6 years is often mentioned.

Do I think it's a big risk? No. But there is a risk.

 

maybe tires do not fail due to age itself, it does get brittle as some have stated. in general when any material gets brittle or hard, it is more prone to crack propagation. maybe not a huge risk of a blown tire with a scratch or two on the tread where it's reinforced a lot more, but on the sidewall?.... something to think about.