Same here. Writing time on 24x and 52x is the same. I noticed that no matter 52x write the data faster, the lead-in and lead-out takes extra time to finish and the final times for 24x and 52x are the same. But I think this is normal. Besides I do not need to write faster than 24x but this is CD
It should have difference between 4x and 16x.
Check the program you use to write disks. When I use nero when I set the settings and set the writing speed to 8x and then I hit new to add the files I want and then hit burn and when the settings window appear it is again on 4x and I should set it two time to 8x to write on 8x speed otherwise it will write to 4x.
Make sure the problem is not of that kind.