The Michelin website has this to say about tire storage. This is basically the advice that has been given about tires for decades, regardless of being bias or radial ply. Of course, these are only the opinions of the tire engineers and the manufacturer.
If tires are on a vehicle parked for a long period, the weight of the vehicle needs to be taken off the tires by jacking it up or removing the tires. Failure to do this may cause irreversible damage.
And Continental says:
As an additional note, don’t let a vehicle sit on tires for extended periods of time. Long-term inactivity is more harmful to tires than weekly drives. Driving on your tires will help flex the tire and maintain oil dispersion within the rubber compounds.
Toyo says:
If you have to store a vehicle for long periods of time, the constant weight on the tires can cause tire damage. If you can, move the vehicle or take it out for a short drive every once in a while – you’ll relieve the stress on the tire and help keep the tire’s rubber compounds lubricated and supple. If your vehicle is stored outside, cover the tires to protect them from direct sunlight.
Yokohama says:
Long term storage, or storage of seasonal vehicles; i.e. RV's, boat trailers and show cars requires special preparations. Vehicles should be raised on blocks, so weight is removed from the tires.
If blocking is not possible, tire pressure should be increased 25% from inflation required for the loaded vehicle. Vehicles should be moved every three months to prevent flat spotting and ozone cracking at the tire sidewall flex point. Flat spots usually disappear, when the tires warm-up, after a 25+ mile drive. Flat spotting, which occurs on vehicles not moved for six, or more months may not disappear.
Tires on vehicles stored out-of-doors, should be protected by opaque covers to prevent damage from sunlight.
Goodyear says:
Ideally, a vehicle in storage should be placed on blocks to remove all weight from the tires. If the vehicle cannot be put on blocks, follow these steps for tire protection:
Completely unload the vehicle so that minimum weight will be placed on the tires.
Inflate tires to recommended operating pressure plus 25%. Ensure that the rim manufacturer’s inflation capacity is not exceeded.
Be sure the storage surface is firm, clean, well drained and reasonably level.
Avoid moving the vehicle during extremely cold weather.
Move the vehicle at least every three months to prevent ozone cracking in the tire bulge area, as well as “flat-spotting” from the prolonged strain of sidewall and tread deflection.
Adjust inflation before putting the vehicle back into service.
It seems that all of the engineers seem to have close to the same opinion of what you should do if you plan to store your vehicle for a period of time. They even talk about flat spots on radial tires. Perhaps they know what they are talking about. :B
