TYRE SHELF LIFE

norman falkiner · 07-22-04, 12:45 AM

It appears that some guys building 40's are buying high performance tyres close to the start of their builds and not as one of the last things to buy. It may be wise to consult with a tyre expert before purchase as these tires normally have a short shelf life and can be very dangerous when they go off. Regards

BenL · 07-22-04, 01:50 AM

Two of the tips I remember for tire (tyre) storage are to keep them out of direct sun light, and away from electric motors and welders (they don't like ozone). Cool, dry basements are a good place to keep them.

killroy · 07-22-04, 06:43 PM

Unless you are buying racing slicks, the rubber in a street tire should last at least a few years on the road. Of course tire life is shortened by tread wear and flat spots from sitting for extended periods.

As long as you follow a few minimum precautions like BenL suggests, their shelf life should be very long, at least five years.

If you intend to race at high speeds, I would reccomend using a tire up to 2 yeaars after manufacture (not purchase). Safe tires are very important at 150 mph+.

For a road car that rarely exceedes 100 mph, a five year old performance tire should be fine.

ChrisL · 07-23-04, 06:15 AM

It’s interesting that the subject of tyre condition should be raised. A week-and-a-bit ago, one of the rear tyers on my GT40 self destructed while traveling along at 100km/h. I felt a short vibration and then a BANG! I was fighting to keep it in a straight line. On inspection, I discovered that the tread and tyre-wall had totally separated. (Not obvious in the pic, but it is all the way around). The tyre dealer is insisting that I had run the tyre totally flat for about twenty kilometers, which is almost laughable.

Has anybody else ever experienced such a failure?

PS. Although I am not dismissing out of hand that I may have had a half-flat tyer, I can say that fifteen minutes earlier I had six observers looking over the car and no one made any mention of a flat tyre. Sixty seconds before the actual event, I had taken a long sweeping corner and the car was as steady as ever.

PPS. On Norman’s original topic, I had bought the tyres 3 months before my expected completion date. As always, the last 3 months of any build always takes 12 months [img]/ubbthreads/images/graemlins/tongue.gif[/img] so the tyers were a year old before they had been used on the road (making them 19 months old now)

JP · 07-23-04, 06:42 AM

Chris,

What pressures were you running?

ChrisL · 07-23-04, 07:21 AM

JP, 35 psi Rear, 28 psi front

killroy · 07-23-04, 02:31 PM

If you had run the tire flat for 20 km, it would not be on the rim, and most of the rim would be gone also. You should contact the manufacturer of the tire. That looks like a manufacturing defect to me.

In the U.S. we had the whole Firestone ATX recall, but that was caused by overloaded SUV's with low tire pressure. A light weight GT40 with a wide tire should be very easy on the sidewall, even with low pressure.

Your GT40 probably weighs a lot less than some cars that use that same tire, probably by about 2/3. So you could run 2/3 the tire pressure of that heavier car with the same ammount of sidewall deflection. I don't think you would be in any trouble unless your pressure was below 20 psi or the tire was defective.

Frank Catt · 07-23-04, 02:56 PM

If you have to keep tyres for any length of time, and if possible from new, wrap them completely in clingfilm or similar tight fitting plastic film. This will keep the solvents in the rubber longer and prolong tyre life. Similarly, if you are storing the car for any period, even just the winter, take the wheels off the car or put the car on jacks, and wrap the tyres as above.

Howard Jones · 07-23-04, 05:05 PM

The only reason a tire would do that IF IT WAS BUILT CORECTLY is if the tire pressure went way down. Thats what they look like, tread seperated from the side wall. That area of the tire is where it is flexing thus the heat build up and failure at the same point. Less than 5-10psi will do it. I had a suv tire on a Chev Blazer do the same thing and the tread came all the way off the tire leaving the sidewalls on the rim. I was in the SNOW speed about 40 mph and outside temp at about 15 dergees F. I first felt a slight softness then a slight vibration and BANG the tread was behind me in the rearview mirror. All in about 30 sec.

When I figured out what had happened I just let in coast to a stop and the rim, alum, was fine. I'm glad you didn't brake hard or you would have flat spotted the rim. All the keep it straight wide eyed arm motion kept you foot off the brake and saved your rim.

I would never believe this story if it had not happened to me. I still find it hard to believe that a tire could get that hot in those conditions. Oh the tread had a nail in it when I walked back and got it. I am not sure how long it ran with a low pressue but it felt ok up to the last min or so.

A light car might not warn you as to a low tire pressure as soon as a heavy one at speed. And as for looking at it sitting in the pits I don't think you would see a low profile tire that was down to 15-20 psi unlees you really were inspecting it. You may have gone out with a leaking tire and it just went down and blew up. These cars handle so well at 8/10s that you might not feel it.

Then again it might have been a bad one, it happens. Any holes in it?

Bill Musarra · 07-24-04, 02:35 PM

You will see the same thing with regular tires as well. Maybe only a slight bow in the base of the tire. My 95 Ram 1500 has the biggest tires alowable on the stock rims which makes it sit a little higher. I towed a "Gator", which is a 1000 lbs. utility golf cart, on a trailer for about 150 miles, after driving the 150 to get it. After arriving home I decided to check the tire pressure all around as the trailer had one of its 4 tires low a week or so ago. For some reason I checked the trucks as well and found one of the rears at about 10 lbs. It didn't look any lower than any of the rest. So looks can be decieving.
Bill

ChrisL · 07-24-04, 09:37 PM

The tyre is currently with the manufacturer and a written report will be provided so I shall wait and see. With regards to a hole in the tyre, the dealer said that he found a “big” hole that I couldn’t find.

Interestingly, the rubber adjacent to the failure point looked very fatigued, whereas the corresponding location on the other side of the tyre looked almost new apart from a little surface smudging from the rims. Should I expect that a flat tyer would have fatigued both sides of the tyre similarly?

In the meantime, the car has been off the road now for two weeks and I'm getting withdrawals [img]/ubbthreads/images/graemlins/tongue.gif[/img]

norman falkiner · 07-25-04, 08:35 PM

I can recall that many years ago when I was running Pirelli P7,s the Pirelli reps would slash any tyres found unused after 12 months to the day of manufacture. I had this confirmed today. My dealer for high performance tyres said they must be "exercised" and he used the example that if I did a track day and let the car sit idle for 12 mths I would need new tyres as the old tyres would have gone off. They would not have the grip that they had previously. Life may depend on make of tire but the sensible thing to do is put fresh tires on at the last minute. Local dealers here would be happy to give you a set of old tyres for the build as they have to pay to dispose of their used rubber. Regards

Kalun D · 07-26-04, 10:34 PM

Tires do have a shelf life. The rubber dries out and gets hard. One thing you can do to slow the process is seal them up in large black garbage bags. So your sealing not only from air circulation but from UV rays.

Also drag racers sometimes use a spray on liquid that is supposed to soften up dried rubber.