File upload and permissions

Hi.

I upload a file with this model :

class Match < ActiveRecord::Base
  belongs_to :contest
  belongs_to :user
  has_many :comments

def replay=(uploaded_file)
    @uploaded_file = uploaded_file
    @filename = sanitize_filename(@uploaded_file.original_filename)
  end

  def after_create
    if !File.exists?(File.dirname(self.path_to_file))
      FileUtils.mkdir_p(File.dirname(self.path_to_file))
    end
    if @uploaded_file.instance_of?(Tempfile)
      FileUtils.copy(@uploaded_file.local_path, self.path_to_file)
    else
      File.open(self.path_to_file, "wb") { |f|
f.write(@uploaded_file.read) }
      File.chmod(755, self.path_to_file)
    end
    write_attribute(:replay, self.path_to_file)
    self.save
  end

  def after_destroy
    if File.exists?(self.replay)
      File.delete(self.replay)
      Dir.rmdir(File.dirname(self.replay))
    end
  end

  def simple_path
    "/files/#{self.id}/#{sanitize_filename(self.replay)}"
  end

  def path_to_file
    File.expand_path("#{RAILS_ROOT}/public/files/#{self.id}/
#{@filename}")
  end

  private
  def sanitize_filename(file_name)
    # get only the filename, not the whole path (from IE)
    just_filename = File.basename(file_name)
    # replace all none alphanumeric, underscore or perioids with
underscore
    just_filename.gsub(/[^\w\.\_]/,'_')
  end
end

The problem is that I can't download the file. The FileUtils.chmod
won't work.
I use apache/passenger.

the file directory :
drwxrwxr-x 4 www-data sobert 4096 oct 16 13:39 files

and in file directory :
drwxr-xr-x 2 sobert sobert 4096 oct 16 13:43 13

and in 13 directory :
-rw------- 1 sobert sobert 275955 oct 16 13:43
Arakan_Citadel_54_mins.SC2Replay

How to set the permissions right In order to allow download ?

Thanks !