Coilovers adjustment?

[stuart182]

Last week I got some used coil overs from goldpedro, obviously they were already set to the ride height he wanted. Which is fine, but all the little speed bumps which have only the middles (no where that the wheels go on) I have to go stupidly slow and try to position the car right, but it still scrapes all along them, For this reason I have to avoid 1 particular way (and a few streets) in my town centre but the only other way in is a 2 mile diversion. The adjusters are pretty seized in place, I've tried getting a wire brush in the clean some of the threads up and some wd40 to ease it up but its still stuck, the whole shock flexes when I try and give it some beans to adjust it. Anyone had the seized adjusters before? How did you solve it?