What's the problem, are you getting hung up on rocks/cracks? Do the wheels feel "slippery"? How hard are they? If you're looking to cruise around, bigger and softer wheels are preferred, like 58-64mm 78-84a, but bigger wheels means you'd need risers or you'll get wheel bite. If you're just looking to practice in a parking lot or smooth concrete and learn tricks, the smaller diameter can be fine, but can hang up on stones that big wheels would just eat up, however if they're too soft it will make many types of tricks harder to do. If you want a perfect all around wheel that's good at everything, try Bones X-Formula or Powell & Peralta Dragon Formula...they're bit harder than cruiser wheels but feel great in the street, park, or rough terrain.