This is a brief but important post about hamster wheels. It does not take long to read through, but I think what this post says is important to any hamster or small pet owner, like mice, gerbils etc.
Most cages come with a 6 Inch wheel in them, but this is not big enough for an adult Syrian hamster. Syrian Hamsters require an 8 inch wheel (minimum) to be able to run in comfort without arching their backs, and causing back problems or other problems for your hamster. A wheel should be available at all times to any small animal similar to hamsters.
DO NOT buy your hamster a metal running wheel. This can be really dangerous for hamsters, as they can get their feet caught between the bars and seriously injure themselves. They can also cause painful sores on hamster’s feet, called bumbles. Stick to smooth plastic wheels where their feet can’t get caught or damaged.
If you have a metal hamster wheel or a wheel smaller than 8", do not panic. Just replace the wheel as soon as possible so that your hamster does not get back or feet problems.