I have a 2007 ford focus. Put new rear drums and shoes. Now it's shaking really bad when on the brakes. Why would new drums and shoes cause shaking? Not the front because u can't feel it in the steering wheel. Help!?

 

Can you be a little more specific?
Shaking can mean a lot of things.
What happens if you apply the brakes slightly?
There are primary and secondary shoes, are they on correctly?
Was any grease allowed to get in the new linings?

Did you do one wheel at a time so you could compare if installed correctly?

 

I am assuming you did the work, it was verified that the correct shoes and drums were used and new hardware was installed.

Remove the wheels and drums. Examine and compare both to make sure they appear to be assembled correctly. The longer shoe should be towards the rear of the vehicle. Were the contact points on the backing plate lightly lubed with grease? When you put your palms at the 9 and 3 oclock position on the shoes, you should be able to rock the shoes back and forth if everything is free and installed properly. If you rotate the drums, there should be a very slight even drag felt with no high or low spots. Finally, as a temporary test, put the old drums back on if you have them and go for a test drive to see if the problem went away.