The Port Elizabeth resident won the 48km PE Masters & Ladies Cycling Club road race on Saturday, which started at Grass Roof Farm Stall by Sardinia Bay, lapped through Maitlands and ended back at Grass Roof.
She then added a victory in the Longmore Classic at Crossways on Sunday.
Although two victories in two days were something special, Shirley realised that competing on consecutive days might not have been a wise decision.
“I tend to push quite hard in the beginning, and in the second half of Sunday’s race I started to feel the effects.
“My legs were getting tired and it also got hot out there, so it was important to manage my pace.
“I also wasn’t at full fitness. I would have suffered less if my training and preparation were where it should have been.
“It worked out for me, though, and I’m glad for the result,” said Shirley, who was second in the Steeltek MTB Classic in early November.
She won the Longmore Classic by a comfortable 16-minute margin, beating Karen Kemp into second place. Melissa Swanepoel was third.
Shirley had no mechanical problems on the course and said she had not experienced too much pressure.
“Melissa pushed me a little in the beginning. She was in front of me for the first two kilometres, but I managed to catch up and overtake her,” she said.
“I’m glad I could maintain the gap, because there were some strong riders. Fortunately, everything worked out for me.”
The 44-year-old Shirley said the single track at the start and near the finish may have favoured her.
“Being a cross-country rider, that’s where I do well. There was a fantastic section of single track in the beginning, which is where I was able to get that decent lead.
“The last six to eight kilometres of the route were also a downhill single track, which is where I picked up the pace.
“I noticed I was falling a bit behind on my tempo because I was trying to keep up with two guys, but I caught up with them on that last stretch.”