Managed to burn 360 back ups on cheap media with standard hp drive

Hi guys just to let you know, i recently flashed my benq drive with i extreme 1.41 @ 12 speed and couldnt get any verb disks so i went to my local pc shop and brought some 8x datasafe dvd-r dl disks, i only have a standard hp drive that came with my desktop. After reading through loads of guides ect i tried to no avail to burn some backups at 2.4 speed all of them were coasters and comming up with dirty disk error, i thought i would give it one more go with the current set up but couldnt be bothered to burn it 2.4 so burnt it @ 8 speed all went well with the burn so i put the disk in my xbox and it went to the black screen as it was b4 so i thought oh here we go again but then to my amazement it loaded up and worked fine, i have burnt another couple of backups at this speed and they all work fine. Just thought i would share this experience maybe someone would be able to shed some light onto why the faster speed works with the cheaper disks. and also wondered if anyone else has had this experience before.