Thanks for the replies, I'll be sure to keep an eye out for those dimples if they're not there already. That's a good point about not commuting very far - if something went wrong with a tire then I wouldn't be that far away from home. The furthest I go is about 20 miles away from home. However, I don't want to be riding on horrible tires because then I'd lose some speed. I'm usually going 18-22mph depending on the wind conditions. Since my budget is tight then I think I'll put some more miles on them and then put the front on the back and buy a new for the front.