Ritek 8x burning slow vs 4x tdk!



Recently got a spindle of Ridata(Ritek) 8x +R. I was burning a DVD about 30 minutes using TDK(Ricoh) 4x +R. After the switch, the Ritek took 8 hrs and it is only 66% done. I am using Liteon 851s (GS0H firmware) with dvd shrink 3.1. Nothing else has changed with regards to my PC. Has anyone had issues after a switch like that. Any suggestions would be great. Thanks in advance.