I am having trouble with the rear ones. The brake piston is too tight and I can't fit it on with my new pads. Is there a tool or different way of getting this brake piston back on with the new pads?

 

You can get a tool like this http://www.sears.com/sr/javasr/produ...seBVCookie=Yes from Autozone for about $8. The rear caliper piston will screw back into the caliper. I had the same issue and the piston wouldn't stay in. Tried it a couple of times and ended up replacing the caliper.

 

You may find a big pair of pliers works better than that cube tool - it did for me anyway. Make sure the wheel spins freely once you get it all back together...

 

you can even do it with the needle noze pliers.
I got the cube though

 

It may also be a frozen caliper if you're having that much of an issue getting the piston to collapse.