Clydesdales/Athenas (200+ lb / 91+ kg) - Uber clyde question, I think?...Brake issues

Hello all....quick rundown, I'm an Uber clyde.....I'm having issues with my brakes. I know this may be a mechanical question, but I figured since i'm a clyde, maybe I could get my answers here. I noticed the when I applied my brake, I heard scraping. Upon inspection of my rear wheel, I noticed that the wall of my wheel/rim had grooves or scratches all along the entire wheel.....I can't see the brake pad being extremely worn. My question is.....could it be due to my weight or is it another issue? This bike is an old Trek 800 mtn bike that I purchased on Craigslist. Your help would be greatly appreciated.

Replace the pads! I'd bet it's not our weight. We have 400 lbs combined weight on our tandem! Sometimes metal fragments of the rim get stuck in the shoes then it scores the rims. I inspect my brake shoes ever few rides or when I hear something scrape out of the norm. I dig out the small frags with a punch or similar.

I once did a very wet descent down a mtn (paved not dirt) road on my road bike. The water and grit sanded my brake shoes down to nothing within a matter of 20 miles. If you get the brakes and rim wet and gritty, that will surely grind them down. One of the reasons I avoid rain rides.

Brake pads are consumables and wear out, it's nothing to worry about.

Like Mr Beanz I've work out pads in a single ride due to large descents, wet weather and the ride leader using the infamous words "I know a shortcut" which turned out to mean a mile of sand and grit. This doesn't stop me riding in the rain and grit, I just carry a spare pair of brake pads and keep and eye on the rim wall thickness.

FWIW, I agree--especially with a used bike, it's possible you or the previous owner got grit or sand stuck to the brake pads. Happens all the time when I ride in the rain, and that can grind grooves in the rim in just a stop or two.
It's not a bad idea to flip the brakes open (easy for me--I have cantilevers on all but one bike) and check them for crud regularly. You can usually brush it out or pick it out with a pointed tool. You can also dress the pads with sandpaper to improve stopping.
If you do have grooves worn in the rim, don't automatically junk them. Rims do wear out, but I've ridden thousands of miles with serious-looking circumferential gouges. Keep an eye on them, but chances are they'll smooth out over time.

Get some Kool Stops

http://www.pricepoint.com/images/styleImages/D_048%20KOOSP2.jpg

^^^
nice cheap upgrade:thumb:

Getting metal fragments in your pads is a normal sign of wear. If you so desire you can be very patient and using tweezers and/or needle nose pliers remove most of the fragments.

It's a lot easier to get new pads.