[PROBLEM] XBian + HFS = read only

[Nicolasrata]

Hi all,
I bought a Pi 2 to do a mediacenter with Kodi and Transmission.
I tried OpenElec, OSMC, XBian, Raspbian and Xbian again.
I have no problem with Kodi.
My problem is with Transmission. I can seed those which are on my hard drive but I can't start new torrent cause I have an error, FS is read only.
I saw there is some problem with HFS file system, but my two 2Tb hard drive are in HFS+ and i can't and don't want to format them.

I tried to mount my drive with rw access but I have an error saying the fs seems to be read only.

So my question is what should I do to have my Pi running Kodi and Transmission with HFS+ hard drive plugged in.

Thanks