My H-line also has the sound from rear everytime i go over bump. The technician try to tight the rear foldable seat for me yesterday and din hear the sound anymore, wish it wont happen again.... 

My rim alwiz bcome dirty coz of something like dark powder and the service center told me it's bcos of the type of brake pad using and oso common problem. Do most persona owner hv tis prob and solution for that??