Rear Brake Problem

[nsgasser]

Hi Guys, this is my first post but I've been lurking around for a while. Great forum with lots of info!

I have an 06 EC300. I noticed that my rear brake took a couple of pumps to get any pressure and upon further inspection, my rear wheel bearings needed replacement. This fixed the problem however after about 160 km I noticed the same thing. Not nearly as bad but still needed a pump before I got any brake feel. There is no play in the bearings anymore and the disk is not warped. When I run the bike on the stand it doesn not happen. I read all the posts I could find here about bearings and brakes and saw a pic of someones spacer (goes in between the two bearings on the sprocket side) and mine is much thinner. I did not replace it when I did the bearings and am wondering if this could be the problem. I really don't want to pound out the new bearings if I don't have to and since there is no play I'm not sure if this is the prob or not. I just find it coincidental that the bearings fixed the problem completely for two rides and then it started again. If anyone has any thoughts they would be much appreciated!