There are a few ways to tell if your RV tires are bad. One way is to look at the tread depth. If the tread is shallow, it's time to replace the tire. Another way is to look for cracks or other damage on the sidewall of the tire. If you see any damage, it's time to replace the tire. Finally, if your RV is shaking or vibrating while you're driving, that could be a sign that one or more of your tires is out of balance.