XRAY - Model racing cars

it cant be the diff, the bearings was in the front.

If you are talking about the large bearings in the front steering knuckles the outside ones will not stay prestine for long. It doesn't take long to put dents in the races of any outside hub bearing. If the bearing still spins but makes noise after THUROUGH cleaning then you probably have dents in the races. As long as it's not terrible you can keep using those bearings for a while longer. Make sure you get ALL the gunk out of the bearings. It's possible they just have some carpet fiber or grit still in them. See TeamGP's FAQ post on this forum about how to clean the bearings.

I had to replace 2 bearings after about 20 runs but that was after some pretty heavy hits to the boards. I'm amazed they were not worse than they were when I took them out.

If you didn't notice the noise on the first run then the bearings were not likely bad out of the box.

Does anyone know if there is anything else that would cause bearings to fail in the hubs accept for hitting the boards?

What wheels are you using?

there are various wheel manufacturers where the hex portion of the wheel is too deep and causes binding when you tighten them down. It literally can pull the races of the bearings apart, forcing the balls inside to wear the races excessively. Other than that, XRAY bearings are the best in the world, IMHO, so it depends on what environment you are running in...sand, etc...

I drive with sorex 28r, and Shumasher wheels.

Tapping the boards will indeed deform the front wheel hub bearings. It doesn't happen all of the time, but one good hit at the right angle is all it takes.

Here's a link to the bearing cleaning post:

http://www.teamxray.com/xforum/viewtopi ... 2907#22907