There are several ways to tell if your bike is leaning or not. Here are some common methods:
Visual Inspection: Stand back and look at your bike from a distance. If it appears to be tilted or leaning to one side, it is a clear indication that it is not standing upright.
Spirit Level: Place a spirit level on the seat or handlebars of your bike. The bubble in the level should be centered if the bike is perfectly upright. If the bubble is off to one side, it means the bike is leaning.
Vertical Plumb Line: Hang a vertical plumb line or string from a fixed point above your bike, such as a tree branch or ceiling. The line should pass through the center of your bike frame. If it deviates to one side, your bike is leaning.
Tilt Test: Place your bike on a level surface, such as a garage floor or a parking lot. Stand behind the bike and gently push it forward. If it starts rolling away or falls to one side, it is leaning.
Tire Wear: Inspect the wear pattern on your tires. If one side of the tire tread is more worn out compared to the other side, it may indicate that your bike is leaning while riding.
Remember, it's normal for a parked bike to lean slightly due to the design of the kickstand or the ground's unevenness. However, if your bike is leaning excessively or unpredictably while riding, it may be a sign of a mechanical issue or improper weight distribution, and it should be inspected by a professional mechanic.