Can only give you pointers from Jozi.
Lots of folk from Jozi ride out to Harties on the R512, then down past Pecanwood, over the low bridge & to the Wimpy / Caltex at the 4-way stop.
Or, N14 to Pinehaven, then to Hekpoort, Bekker Schools, into Magalies (super kak road, plus Magalies Wimpy is...