What is the best way to measure the front and back brake pad thicknesses? Do I need to take off the wheels?

What is minimum, safe thickness?

 

You can take off your wheels to look at the "pads" but, IMO, you can also look through openings in the wheels to see what the status of your pads are. I do not know what the OEM thickness for the pads is but if you call Sewell parts department, I assume they will relate that info to you.

 

I just turned on my Droid X flashlight and it is easy to peek through the wheel spokes and see the pad thickness in my garage. I like to replace my pads when they get thinner than 1/4 inch. Under no circumstances would I let them get down to 1/8 inch because they are a thermal insulator between the hydraulics and the nearly redhot brake rotor. You want plenty of insulation there or you will cook your hydraulics sooner or later. Just pop in new pads and do not machine or true-up the rotors. Rotors should never have any metal removed from them or they lose their braking capacity. Unless they are warped, just rplace the pads and move on. If your rotors are warped and you get that shudder when braking, put new rotors and pads on. Warped rotors can not be fixed by truing them up. These parts are cheap if you shop online here and maybe elsewhere. Its the labor that costs, but replacing brake pads is easily done by most any shadetree mechanic. Spend some time and study it first (that's what search engines are for) if you are changing pads for the first time. Better yet, get a buddy who has done it before to help. It can't be that hard because I have done it on many of my cars. JMHO.