Cleaning Bearings

Question
Hi. I bought a Rolleblade Roadrunner Pro44 and I've been trying it around. As I got a lot of dirt during my last time, I decided to clean the bearings. I wasn't aware of many details so I did what I tought was reasonable... I removed the wheels, cleaned the dirt with a cloth and sprayed some WD-40 on it. But then the wheels became noisy as if some dirt was inside of the bearings. I realize now that if the bearings are sealed, I shouldn't have cleaned it with cloth. But how can I know what kind of bearings I have? And how to get the bearings to be smooth again? Do you think that just grease will solve it? What kind of grease should I be using?
Thanks in advance!

Answer
There are usually 2 kinds of bearings, sealed and serviceable. The latter being the type that you can take apart and clean. Either type can be soaked in some type of de-greasing cleaner or sprayed with WD-40, but then the grease needs to be replaced in order for them to spin smoothly. You can use specified bearing grease, speed oil or just plain pld white grease that you can get at a hardware store. You will have to work it in with your fingers and the bearings may seem stiff at first, but the grease will work it's way in and break down a bit as it gets used.

Good luck.