I've brought a set of 312mm calipers for the vrs and started to clean them up a bit before I paint them. I've used a wire brush on a drill but there still a rusty.

What's the best way to get it off and hopefully smooth.

Ant

remove as much rust as you can how you're doing it then give them a coat or two of red oxide paint as a primer.

A wire brush on a drill and a spray with Primer
OR

Powder coating is not expensive..Do a search of firms that do it

Theres one near me called Cas Coatings

They Shot blast them and Powdercoat in a colour of your choice

Heres a good one:

HERE

Cap any "clean" surfaces and sandblast. 

When I did a set of mine I just wire brushed them like you then I gave them a coat of rust converter, this is the stuff I used http://www.frost.co.uk/review-granville-heavy-duty-rust-cure. Then I de-greased them and applied some paint of my choice. Maybe a little overkill but I already had the rust converter so I thought I might as well use it.

 

This is what the looked like

 

This is with a coating of Rust converter you paint it on and it looks like milk.

 

 

Once it dries it turns the rust black by chemical process.

 

 

Then I painted them giving them 2-3 coats. That little tin you can see easily did 2 pairs of calipers which I brought from amazon.

 

 

 

Here's the other set I did.

 

I lust gave mine a quick going over with a wire brush as they were still on the car and sprayed them with Hamerite. It's still on and strong As long as there is no loose rust it says it can be sprayed on rusty metal so all is well. As for the drums on the back I gave them a better scrub with the drill brush.

I didn't really want to strip them down. I'll just have to keep trying with the drill and wire brush.

Ant

I gave mine a going over with a wire brush on a drill to get most off it off then attacked it with a dremel and a load of small wire wheels. Ended up lovely and smooth (but not so much that paint doesn't stick)

You won't get them completely smooth without putting in a lot of time and effort because I believe they are made from cast iron. Once you give it a few coats of paint it will smooth out a lot of the ruffness but to be honest you'll never notice them from behind a wheel anyway.