Bit rate is fixed by source but you can increase the buffer size to reduce buffering.
Press pause and let it buffer for a few minutes, that often helps.
You can also try some lower quality streams - my two favorites are:
969dbafa76bbd0ca37d73629f392c83fcf9cc295
53793f3854af450d1c62dc9c3f659e60e7b99400
and here are 2 HQ streams with many peers at the moment:
Sky Sports F1 HD - 1080p 6000kbps 8ea4f336595d7a957ff51ffe5ff5a1dc10c60000
Sky Sports F1 HD - 720p 2000kbps e42460fdf545a96abd3a73e6e4c33c7e4f87abb7
p.s.
if you have switched streams it may help to close the ace client in the system try first to flush existing peers.
You can also change your options in the system tray client, mine are:
