DTS Harsh Ride

Well, there appears to be no way to manually switch modes (ref. Service manual), and without a DTC being set, there is also no way to determine if there is a problem with the RSS selecting the correct mode for the surface/speed. It still seems to be too harsh on smooth surfaces, but performs great on rough roads. I will need a tech scanner to check if all functions are working properly. Thanks.

The scanner needed is the certified GM version programmed for this specific vehicle's suspension and Bosch CVRSS, which is damn hard to find outside a GM shop (and usually only a Cadillac dealer at that, and they sure don't lend them!). As for a wheel shop that will do on-car balancing, no luck with that here. I checked thickness and runout on both front rotors - thickness on both had no measurable variation around the surfaces (less than 1 thousands of an inch variations). I cleaned all caliper bracket, rotor and wheel mounting surfaces, and installed the rotors on the car. The right one was right on (no measureable runout laterally or vertically). However, the left one showed a lateral runout variation at one point of 5 thous, with no vertical runout. When I mounted the wheels and checked the wheel runouts, I got the same results. According to GM, this variation is well within spec. I changed the pads, just to be sure - still no joy. Like I said before, this is puzzling - the only conclusion I can draw is that no company makes a perfectly round perfectly homogeneous tire for this car, and that the smallest torsional imperfection reacts badly with this RSS. But thanks anyway.