Hi guys,
been searching around the net, but haven't been able to find a really good indicator when to change or resurface the rotor. I know it's time to replace my brake pad (my car just hit 40k). Is there any indication if the rotor needs resurface or I DO need to resurface or replace it everytime I replace the brake pad? I'm doing this DIY for first time that's why the question. ^.^

Any input is greatly appreciated. Thanks.