Do tires have an "expiration" or age limit?
 

:notamused:I found a couple of brand new tires that had been in storage since probably 1995. They were Velociraptors with less that 100 miles on them. Good MTB tires.

I used them for @150 miles, mainly on pavement. I noticed that the outside knobbies were pulling loose. Is that because of the pavement, the age of the tires, both, neither? Should I just trash them at this point?

Well for car tires they should be replaced at 6 years regardless of wear. Bike tires are constructed similarly, and I am sure suffer the same age related decay as do belts and hoses.

The rubber and other synthetic materials harden, become brittle, and crack with age. Some tires last longer than others. I've seen printed warnings to replace car tires within 3 years but that seems extreme to me. Mine go longer.
I had a car with old expensive tires that had been stored several years. The treads showed very little wear but two of the tires came apart and blew out at different times while on the highway. I suppose it could happen to old bicycle tires as well.

Al

Depends on how long and where the tires were stored. With the prices for new tires, why not buy/use new ones. Hard to trust tires that has been stored for years. UV, Ozone, cold/hot cycles, and general drying out of the compound compromise the safety factor and grip/handling. From the OP's description, the tires are falling apart at the edges already, so why fool around any longer?

I used some NOS tires I had stored for years for local runs only (5-10 miles max distance) for about 6 months. The air pressure had 'inflate until hard' molded into the sidewall as well as the max pressure...that's how old those tires were (Union Tires...was good stuff back in the day and wore like iron/long lasting block treads). No cracks in the tire or sidewalls, but decided to buy new tires anyways.