I own a 1930 Model a Ford cabriolet on which a frame-up restoration was completed in September 1988. At that time new tubes and new Firestone 4.75-5.00x19 tires were installed. Since then the car has traveled just less than 5,000 miles and always been garaged.
The local Goodyear dealer tells me that the tires show neither crazing nor checking. His opinion is that replacement of the tires is not necessary.
BUT… they will be 20 years old in just a few months!
Is age alone enough reason to replace these tires, or should I wait until the tire carcasses shows evidence of deterioration?
If the tires are not dry rotted I would keep them.
You should also capitalize “A” in Model A 
I’m somewhat surprised that they’re not showing even a bit of cracking at this age, but if the car has been stored in a climate controlled environment away from the elements it is possible. I’m guessing it’s likely that you never take this car on the highway and use it for around town or 45mph or less driving. If that’s the case I’d keep going with them because even if you experience a blowout it isn’t likely to be a serious situation. In the end the best choice is what your gut tells youo because we can’t see the tires and we don’t know how you drive.
The admonition to replace tires due to age applies to tubeless tires. In your case the tubes are doing all the work. Keep your current tires and carry a spare tube.
I add this suggestion. If you keep it mostly ‘garaged’, jack up the vehicle and place all four wheels on jackstands. It will eliminate any flat spots that may develop in the tires/tubes. Another benefit is you can spin the tires around to keep the wheel bearings’ grease functional and evenly distributed.
Loafer: you?re right about the ?A?.. and if you saw this car you would know it should definitely be capitalized! A real gem.
Dave G.: environment is really not climate controlled. Car lives in an adobe garage with the temperature ranging from high 40?s in deep winter to 80?s in midsummer. You?re right; all travel is local with speed never over 45 and usually 20 to 30 at most.
Steve F.: point about tubeless vs. tubed is well taken; hadn?t thought of that.
profhandy: good idea. Will do as you suggest next winter.
Ozone is what causes rubber to crack. If the vehicle is kept out of the light or the tires covered, they should last a long time.
If your tires have nylon fabric reinforcement (cords) then I’d be inclined to keep them if they show no other signs of deterioration. If they have rayon cords, then I’d be inclined to replace them. Nylon is very durable over a long time; rayon is not; good for about 5 years.
After 20 years i’d definitely replace them. Coker tires make reproduction tires for classic antiqes that meet modern safety standards. Check out their website.
There have been a few recent bulletins issued by tire manufacturers to the effect that tires can degrade over time and the limit is between 6 and 10 years. These bulletins are obviously applicable to modern radial tires used the way tires are currently used.
The situation expressed in this thread seems to be one of those “exceptions to the rule”. Modern radial tires do deteriorate over time and particularly lose their ability for their belts to withstand centrifugal forces. However, a Model A’s speed capability is pretty low, and the tires are not belted.
The best information I have is that this type of tire will fail by throwing chunks of tread off- and not lose inflation pressure. The tread will bulge out shortly before it actually chunks off - and that ought to cause a vibration, but the speed of the Model A is slow enough that the bulge might not be detectable.
So the question comes down to how much risk are you willing to take. It’s the cost of tires vs some body repair.
When in doubt I always prefer to err on the side of safety. I still recommend a new set of Coker’s.
Interesting replies; thanks to all. 20 years seems a long time for rubber- tubes or tires- to retain the characteristics it possessed when new. And if a tire or tube should fail, even at only 25 MPH or so, the event could be exciting… which I don’t want… and I certainly am not interested in “some body repair” of the car or me.