Doing tires manually can sometimes be tough, but very convenient and rewarding. As the previous posters mentioned, the middle section of the rim is a depression and making sure that the bead isn't actually on the bead and in that depression will ensure you have enough bead slack to get the upper end down over. If the bead of the tire is on the seat of the rim before you get the bead of the tire over the rim it will tension up and be impossible / cause damage to the bead of the tire. Longer tire irons (if you're using short ones) are easier. Having a bottle brush esp. with a lil sponge on it and some dish-soapy water to rub on the bead for lube also can really help. I've always had good luck inflating bike tires, car tires can work well but larger ones or large sidewall flexible ones I've had to strap around to the rim or ignite starting fluid in them to seat. Again as mentioned before after doing it a couple times and getting the hang of it it becomes less challenging / frustrating once you know the details of the process. I personally love doing it myself, changing a tire out in about an hour without paying, having to take them anywhere and wait etc. is awesome! I have been not bothering with balance for awhile, I notice a lil vibration but nothing major. You can buy a gravity balancer for bike tires for under $40 (at least when I bought mine) and that's pretty easy too. Then to trust your swingarm notching (I've heard this can be unreliable) for rear wheel alignment or use a caliper to measure both sides for better precision.