Thomson, who turns 51 next month, will be one of the older riders in the field for the 60km race, but said this didn’t bother him.
“I took some time off after the Epic. I want to try to give it a go but at the same time enjoy it at the Karkloof,” Thomson told In the Bunch.
“The younger guys definitely keep me on my toes. You have to be careful, because you often try to hang on longer than you actually should.
“Then you end up paying for it later because you are not able to recover as quickly as the young guys do.
“But I love racing with the youngsters and I enjoy mixing it up if I can.”
He is looking forward to the technical routes Karkloof offers. “The more technical the better, for me,” Thomson said. “I used to do a lot of cross-country and lap-racing, so I enjoy the technical side of it.
“I enjoy the shorter, punchier climbs – that is where I perform my best.”
Thomson racked up 152 caps for the Sharks between 1989 and 1998, 26 caps for Saracens until 2000 and he featured in four unofficial Test matches for the Springboks in 1996.
He became a “natural” in cycling when he took up the sport at the age of 35.
“Two years after I finished at Saracens I started cycling and I loved it. I took to it like a duck to water. It was easy in terms of injuries and on the body, as it was not weight-bearing.
“Cycling offered the full test of my aerobic ability. I missed that on the rugby field after I stopped playing and it filled that gap.”