weak rear brake

First post for me. Thanks for all the great tips and tech info on this bike! I feel like I am way ahead of the ownership game with this site and all the knowledgeable people on it keeping us informed.

I've had my 2008 SD since Jan 10 and in addition to the surging issue (which I've done lots of reading up on from various threads) I have a rear brake problem no one else seems to be complaining about. The lever feels fine for the first second it is down, even though the brake itself isn't that powerful (fine for me as it is normally only used at stoplights) but then immediately gives way under my foot, as if all the fluid is getting pushed out. The lever then sits too far down for me to really put some weight on it and is so ineffective I can just roll the bike ahead a few inches with the lever still down. If I let off the lever and press again the same thing happens--initial bite but then more lever travel and almost no brake.

Bleeding the brake did nothing to alleviate the problem. I did a forum search and couldn't locate any other references to this type of rear brake issue.

Any ideas?

This is not normal. Grendel's rear brake is perfect. Not too powerful but lots of feel. He can lock up the rear at will. It is very linear.

Did you get this bike new or used? Check for any leaks. If nothing there then the master cylinder is suspect. Bad seal or something.

The Superduke back brake is a joke. A bit like the horn. Not quite in the same calibre as everything else on the bike. I use the bake brake for steadying slow riding through traffic and sometimes up to corners but no matter how hard I try I've never been able to lock it up.

Just fitted a set of rearsets today and the rear brake master is fitted differently and the manufacturer supplied a new brake hose to make it fit nice.
All I can say is that the rear brake takes a while and needs patience to get it to bleed properly. If you take your time and do it right it brakes fine!
I can lock the rear wheel no problem.