I also have G015 215/65/16, no complaints.
If you have time, and if it's possible, raise the car a bit. It helps.
Also try to invest in a sumpguard, there are some nasty bits of road in Baviaans.
Take a whole day for Baviaans's eastern side, and western, for that matter, there's lots to see.
On the eastern side, watch out for the Fortuners and Cruisers with Caravans coming thru in the passes, it's narrow in places.
If there was a lot of rain, they'll probably not let you drive West-East. Have a plan "B".
There is 1 water crossing wich can be a problem......
Fill up before you enter Baviaans, there is no petrol inside. (Take spare fuel if you can, especially if you are driving around a bit).
If you are looking for a place to stay on the Western side of Baviaans, I can recommend Verberg Herberg.
Inside Baviaans, there are quire a few places, but Makkedaat (Caves) is something special.
Zuurberg is a nice pass. (any Avis car can do it.

) It is a bit rough(washed out) in places.
Avoid Ann's Villa if you want to sleep over. (northern end of Zuurberg). It's a dump.
There is a "museum" of some sort, try your luck, we didn't have time.