First, let me preface this by saying, I am still new to the myriad nuances of multiple chainrings/cogs, and derailleurs (I've been a fixed-gear rider for waaaay too long).

I bought a used road bike. It has an 8-speed cassette and a triple crankset. When I got the bike there was a 10-speed chain on it. This was doing nothing but causing shifting problems with the front derailleur. I swapped it out for an 8-speed chain. Now everything seems to be running like clockwork. However, I've noticed a few spots (scrapes marks) on the large chainring where the chain has rubbed during shifting.

Is this normal? Or perhaps the 8-speed chain is too wide and should switch to a 9-speed chain? I have no idea what speed (8 or 9?) chain the crankset was intended for.

Thanks.