Thanks Kevin. Yeah, I typically do spares and not backs as well. Usually test doneness by doing a "mini tear" test with my finger. General temp info is handy. Between the two, then maybe I would do a manual test, tearing off a rib.
If I want to do high temp rib cooks just looking for a general temp to start watching. Knowing that temp alone won't tell me when it's done. Thinking that a high temp cook to 200 deg or so on spare would or could be a watch point or foil point.
Just more info. Don't know if it will change my method. Really have found that Therma Pen handy though, cooking in and out of doors.
Johnny - I would leave things alone at 250 deg or so cook temp but start checking for doneness around 4 hours in with baby backs. I find they can get done quicker than I expect sometimes. Then again if you are doing a 3-2-1 method you will be checking before then anyhow. I have had times when baby backs at 250 to 300 deg have been pretty much done at 4 to 5 hours instead of the typical 6 hours plus.
Ray