It will be the fourth time Shirley tackles the event. Last year he managed to break his personal record when he clocked 6:31:16.
“Winning it for the third time in a row will be a great achievement,” Shirley told In the Bunch.
“I know I will be up against some stiff competition, such as Jason Meaton, but I will just have to pace myself properly.”
The 48-year-old said he would need to hold his own through Longmore up towards the King of the Mountain challenge.
“It always goes up fast there and there is a lot of climbing. Getting to the top of the mountain in good shape will be my goal.
“The youngsters will probably try to take it there and push the pace a bit. I also know that I’ll be marked and they’ll try to get away from me there.
“Then going down towards the Elands River we may ride against a headwind. I will just have to keep my head down and ride, which is what I do best.
“I do a lot of wind training which helps a lot in a race like this. Last year I rode on my own from there,” Shirley said, as he beat the second-placed Steven Venter by a comfortable 14 minutes.
Shirley admitted he did not have the same level of preparation as last year, but said he would just “try to ride my own race”.
“Hopefully I have the legs. We’ll have to see how it goes. My number one aim is to ride my own race and if it goes my way I will be up there. If it doesn’t then I will just have to fight another day.”
Despite a possible lack of preparation Shirley said he remained fit.
“I have been doing a lot of multi-sport, which includes running and swimming. I have not done the kind of mileage that I did last year due to an injury which hampered me slightly.
“I have still however put in many miles, just a little bit down from last year.”
The Trans Elands was one of the toughest races he would normally take part in, Shirley said.
“It is a big race and there is a lot of preparation that goes into it. It is probably one of the toughest ultra-distance mountain-bike races on my calendar.
“But I am confident in my abilities if I stick to my game plan.”