I have a old car I only drive it abot 20 miles a year the tires 35 years old .The tread is good . What should I do to keep them from cracking?
Place the vehicle on 4 jack stands, in order to take all weight off of those ancient tires.
What kind of tires are they?
If they’re some sort of super-thick truck tire they may be okay, but if they’re just regular old passenger radials (or bias-plys!) you should probably seriously consider replacing them. Are you sure they’re really 35 years old? Have you owned the truck since it was new?
My 79 c10 pickup, with only 70,000 total miles on it, is on it’s third set of tires for just one reason.
age. ( & parked outside )
get those tires off of there.
Get them off even if 20 miles a year. You are 25 years past any preservation idea. Even if it’s 20 miles per year, it’s not if…it’s a soon-to-be when, as in blowout. Don’t put yourself and others at risk. At least get a set of marginally good used tires from a tire shop. Lots of shops limit used tire sales to use as spares. But under your circumstances, they will probably help. Your case reminds me of a major safety issue that needs attention when you find it. That’s Grandma’s car. She is still driving the last car Dad bought before he died. That was 10 -15 -20 years ago. Grandma puts on maybe 300 miles a year. Tires look brand new. Tires are rotten. This gets even worse when one of the grankids or someone else ends up with Grandma’s car.
35-year-old tires are not safe to drive on, regardless of the tread depth. Nothing you do will prevent them from cracking. The rubber compound is breaking down as a result of age.
Your truck needs new tires.
If you want to keep the old tires for show purposes, get another set of wheels and tires to use for driving, and put the wheels with the old tires on when you get to the show.
Or buy reproduction old tires from someone like Coker.
Just don’t expect them to last 35 years.
I would not use 35 year old tires, even at parade speeds.My old '76 Dodge 1-ton rides on 20 year old Kelly nylon 10-plys (7.50x16) and hauls 800 gallons of water over washboard dirt roads once a week…The tires have been trouble free…Tires are a lot tougher than you think…
Radial tires are much more sensitive to aging than bias tires ever were. On the other hand, radial tires out perform bias tires in almost every aspect.
Recent bulletins from the tire industry indicate that tires degrade simply due to time. The age of a tire is important even if the tire is unused. The limit seems to be 10 years in a cold climate. (and I’m sure their recommendation is for radial passenger car tires.)
But even if you have bias tires, the odds of something bad happening are starting to add up. Just remember, that even “One in a million” means that it happens to some ONE - and if you can avoid being that one, you should.
Tyres are a very important part of the safety of any vehicle. A marginal tyre may last a long time, or it may fail today. Old tyres are more likely to fail today so I believe it is both foolish and irresponsible to drive on public roads with them.
The argument that it has not happened yet does not convince me and it should not convince you. Most of your advice is great and in general I agree that you know more about cars than I ever will, but safety should not be taken casually.If your tires have nylon fabric reinforcement, I am not particularly surprised that your tires have lasted this long. Nylon heat ages very well making it even more stable at temperatures where people can be. If this vehicle is used at low speeds such as 30 mph or less, a blowout should not be a traumatic event unless you panic.
The rubber will gradually be destroyed by ultra-violet light. If the truck has always been parked in the dark (not likely), the tires MAY still be good.
Some years ago I replaced the tires on my camper since the rubber was cracking even though the tread was hardly worn. This RV unit had been parked and stored outside and was 18 years old.
My advice is to buy inexpensive new tires and cover them up when you park the truck.
I have never seen a tire that has failed simply because of age…Now I have seem some old tires that have been allowed to go flat for a year or two and when someone attempted to pump them up, the cracked side-walls split open…So I guess you could call that an age-related failure…But you are right, passenger car tires with their one or two ply sidewalls are not going to last forever…You can almost stick your finger through them when they are new…
“The rubber will gardually be destroyed by ultra-violet light.”
I’m skeptical of that claim. Certainly ultraviolet light will break chemical bonds, but only at the surface. The light won’t go more than a few nanometers deep before it is absorbed. And when the bonds are broken, they will reform with another ion.
jt; whatever the action is, my trailer tires were completely cracked through at the tread level The light and ozone weaken the rubber over time and the internal pressure makes the cracks bigger. It’s interesting that some old army trucks were found in the North African desert, after 50 years, covered with sand. The tires on them still had lots of air pressure and they had no cracks!!
I have never seen a tire that has failed simply because of age.
No, but how do you know if a tyre failure was do to age or something else, or most likely a combination of factors, like hitting a hole with an old tyre. It would not have failed if you did not hit the hole, but it likely would not have failed if you have a good, not too old tyre.
“I have a old car I only drive it abot 20 miles a year the tires 35 years old .The tread is good . What should I do to keep them from cracking?”
Drive them only 10 miles per year… 
If the tires aren’t too cracked up yet, use a product like Turtle Wax Wet’N Black.
Since you are obviously only concerned about appearance and safety is not an issue, a product like that should do the job.
…“I have never seen a tire that has failed simply because of age…”
I’ve personally seen several examples of tires that were stored in trunks that blew up after being there for many, many years. I’ve also fielded stories of the same type of thing.
So while it may be difficult to document if UV or ozone or time is the cause of a specific tire failure, there are enough documented cases to add credibility to each.
Wow! Doc, that is amazing! Good story, thanks.
In addition to the elastomeric component of the tires having long ago dried up and lost their elasticity, making these tires unsafe and prone to cracking and sudden failure, tread and tire compounds and designs as well as the belt fibers are now far better than they were in 1974. New tires would enhance the handling and safety even of the old ones were in perfect shape.
It’s time for new rubber. Modern ruber.