When to replace tires? The smart answer is when they’re worn out. That won’t do you any good though, will it? Molded into the tread of most tires are a series of bars that run parallel to the sidewall.
These are called wear bars; when they become visible the tire is shot, plain and simple. Failing that, any time the tread becomes shallower than one-eighth of an inch, start thinking about replacing the tires. Picking a New Tire, Of course, you can always replace your worn-out tires with the exact same make and style, if you are 100 percent happy with them. We all know that’s not always the case.
There are only a couple of hard-and-fast rules when it comes to replacing the tires. The first is to never replace a tire with one that has a lower speed rating than the original equipment. The second is that rims are designed to support tires of a certain width. Putting on a big fat tire won’t help much if the rims on your bike are intended to take little skinny ones.
Finally, all the information you need to safely choose a new tire is stamped right on the sidewall of your old one.