Why a Swivel Wheel Usually Follows the Cart
A shopping-cart caster is a wheel mounted in a fork that can rotate around a vertical pivot. The wheel’s contact point sits slightly behind that pivot, an arrangement called caster offset. As the cart moves, friction between the floor and tire creates a turning force that swings the wheel into line with the direction of travel—much like a small trailing wheel on a suitcase.
That self-aligning action works only when the wheel and its mount can move freely and sit in the intended geometry. If a wheel is bent, its pivot binds, or its tire wears unevenly, it may settle at an angle instead of neatly trailing the cart.
How One Caster Starts a Tug-of-War
A misaligned wheel pushes sideways as it rolls. The cart’s frame transfers that force to the handle, so the shopper has to steer against it. The other casters may point in different directions as the cart turns, making the pull feel intermittent: the cart drifts, resists a correction, then veers again.
The effect can be surprisingly noticeable because the shopper is trying to guide the whole cart through the handle while each wheel meets the floor separately. A small sideways force at one corner becomes a repeated steering demand over every aisle-length stretch.
Why the Problem Can Feel Unpredictable
Swivel casters are designed to pivot, so a wheel’s direction changes during turns and when the cart is pushed backward. That normal freedom makes a damaged or stiff caster harder to read: it may behave acceptably in one direction, then swing into a troublesome angle after a turn. The result is not simply a cart that rolls less smoothly; it is a cart whose wheels disagree about where the cart should go.
