Do you always have trouble with the girth rubbing and causing sores while you're riding? It is possible to prevent this common problem; here are some solutions.
A girth will rub is if wasn't tight enough while you were riding. It's very easy to have this happen because most horses blow their stomachs up a little bit to resist the girth while you're tightening it. Even if you walk your horse for a bit and check it again before you get on, once your weight is in the saddle and you're working, that's when the horse finally lets go of that blown-out stomach. You need to get off the horse and check the girth again before beginning your workout, and you'll usually find it can be tightened another notch. This will keep it tight and prevent the rubbing that creates the sores.
Make sure you have a girth that is the right length. Too short or too long are both problems. If the edges of it come all the way to the buckles, then it is too long and you need one a couple inches shorter. If it only covers the bottom part of your horse's tummy, then it might be too short.
Next, consider the type of girth you are using. If you are using a neoprene girth, consider switching to a fleece girth, or getting a fleece girth cover, and vice versa. There are also contoured girths with cutout areas behind the elbows, which can help stop girth galls. If you go with this kind of girth, just make sure it fits right. A rope girth for western riders might work too. Whatever girth you choose, make sure it is clean and free of any debris before you put it on. Even a sweat-stiffened girth can cause rubbing and sores, so clean it every time you ride. As with all horse equipment, keeping it clean will prevent or fix ninety percent of problems.
Essentially, the cause of girth rubbing may be just the way your horse is formed. My quarterhorse has big barrel belly that forces the girth forward into her elbows. With that situation, it seems like girth galls are just bound to happen, but changing girths every time seems to help. A fleece girth for one ride, a neoprene girth for another ride and I always make sure the girths are clean and free of old sweat before riding. Sometimes, that's the best solution.