I just pulled the rotors and calipers from my '97 Astro AWD to replace the whole thing. Took the rotors to the shop to have them turned, and was told that they didn't have the right adapter to accommodate the composite hub.
I then took the rotors next door to the garage and was told by two people - independently - that they had to be turned on the van or they would not turn true.
Back at the auto parts store the guy said that wasn't necessarily so. He said that technically, yes, you should turn them on the van so that everything is perfect, but that it is possible to get a good true job otherwise.
Does it make a huge difference? Since I have to put everything back together to drive the van to the garage to have the rotors turned I went ahead and made an appointment for two days from now to just have them do the job - it's only about $40 more than I would pay for the parts myself and I trust the shop's work - but I'd like to know how big of a deal this is.
TIA,
Karl