One of my members and friends recently suffered from some tire problems which took him from having a good tire to one that was bald to the radial plies. This is called delamination and has the potential to put you in the hospital or worse in the morgue. Delamination can cause a substantial chunk of the tire to come off at high speed. At times it does not come off cleanly and can get caught in your fender or swing arm and cause the rear wheel to lock up. That can lead to having a very bad day.
This is a phenomena more common to car tires than to bikes but it can happen. You may have heard about the spate of roll over accidents with Ford Explorers that was caused by tires that were overloaded, defective and under inflated. The two key terms to look at is defects and under inflation as it pertains to bikes.
Tires are not made of solid rubber. If they were they would just keep filling up like balloons and would not be stable. Instead what they consist of is layers of synthetic fabrics called plies usually made from Rayon, polyester, nylon and Kevlar. They are laminated in a pattern to minimize rolling resistance so the fabric folds as it transitions from round to your flat contact patch. Manufacturing tires is a complex process that requires a high level of technical skill and strict monitoring of manufacturing processes. The vulcanized rubber shell which is molded around the fabric core under normal circumstances does not want to adhere to the plastic fabrics. Proprietary techniques used by manufacturers solve these problems but at times, quality control failures can lead to batches of tires that are prone to delamination. So delamination is a defect due to incomplete or poor adhesion of the tire tread to the plies. This could be due to contamination, improper curing or defective materials. It happens to the best manufacturers. What exacerbates it is also under inflation and damage due to our crumbling infrastructure ie roads. Pot hole impacts when under inflated starts the delamination process on defective tires.
So what can you do to prevent becoming potential road kill over your tires? Do your home work. Don't just read reviews because one of the fastest growing industries is burying negative information about products on page 15 in google. Instead use key words like recalls or delamination or tire failures. This will bring up technical discussions about issues with a particular brand, type or size. Just because one tire group is bad doesn't condemn other types within the brand. Sometimes you'll read postings about problems on forums before it becomes a national campaign because sometimes companies are slow to do a recall unless the failures reach a certain threshold. When you only have two tires even gossip has to be taken seriously.
You should do monthly tire inspections looking for nails, screws and bulges emanating from the sidewall or tread. If you go through a nasty pot hole you should keep an eye on the tires as it can take several days for a problem to manifest itself. Most failures seem to happen in hot weather and at high speeds but this is not a hard fast rule. Only vigilance can keep you safe and staying informed.
When buying tires especially online, pay attention to the date of manufacture. It is molded to the sidewall of the tire as depicted below. New old stock is not the same as new. Even if a tire has never been mounted because rubber is an organic material along with the special adhesives that were used to bond the carcass to the plies, it can deteriorate over time. Tires that are 3-4 years old should be replaced even if they have plenty of tread left and have been sitting in a garage. If they are 4 years old and new, is it really worth the risk of entropy.