Wheels can make quite a difference. The most important thing for a larger rider to consider is wheel strength. If your wheels aren’t strong enough they can go out of true. When a wheel is in true it is perfectly straight. If the wheel takes a hard hit it can get slightly bent or a spoke can break. Breaking a spoke will also affect the tension of the wheel making it go out of true.
The rim material is also important for braking. If you live somewhere rainy you want to avoid steel rims because you wont be able to break as easily. Aluminium is a much better stopping surface than steel and pretty common with newer bikes.
The wheel size will affect the durability. The smaller the diameter of the wheel the stronger it is. 26″ wheels are stronger than 700c wheels. The main problem with the smaller wheel is something called rolling resistance. See Sheldon Brown if you want to get technical. Rolling resistance isn’t much of a problem unless your aiming for speed. It’s also easier to get going from a dead stop with a smaller wheel than a larger ones. There are other wheel sizes but these are the most common you will see.
A slick 26inch tire is going to be much easier to use than knobby mountain bike tires. Unless your riding off road you don’t need need the knobby tires. secondly keep your tires properly inflated and you should be in good shape. As far as pumps go, if your not going to carry one with you don’t buy a travel pump buy a floor pump they are much easier to use.
When looking for rims try to find a touring rim. These are often double walled are really strong. Again made for carrying a load. The rear wheel is the most important wheel to for strength since it carries most of your weight. I am a huge fan of Mavic A719 for a 700c rim. They are super strong.
A strong rim is especially important if your buying a 700c because they are more fragile. If you have 26″ rims they are stronger and you may not have to consider further action.
Spokes: The more spokes you have the more your weight is distributed. If your can find a wheel set with double butted spokes they will be even better because they disperse the load over the spoke better.
If your are buying a brand new bike you may not have control over some of these thing if you get a bike that’s already built up. Wheels with double butted spokes must be build by a person thus making it much more expensive. Make due with what you think you’ll and if it becomes problematic you can invest in a new wheel or wheel set.
next up saddles!