Together with Pipo Derani, the Action Express Racing Cadillac driver holds a slender three-point advantage over Wayne Taylor Racing with Andretti Acura drivers Ricky Taylor and Filipe Albuquerque ahead of the decisive 10-hour enduro at Road Atlanta later this month.
AXR's only win of the season to date came at the Sebring 12 Hours, after a multi-car incident in the closing stages boosted the car Sims and Derani shared with third driver Jack Aitken from fourth to the lead.
But it has been a consistent points scorer in the first season for the new hybrid GTP cars having registered additional podiums at Laguna Seca and Watkins Glen.
However Sims concedes that, having not added to its podium tally in the last three races, the 2023 campaign hasn't always gone smoothly for AXR.
Despite setting fastest lap at Mosport, the Cadillac ended up seventh as its strategy failed to pay off. A warm-up crash for Sims on cold tyres at Road America required hasty repairs and compromised a race that they would start from pole, ending up sixth, while a brake issue at Indianapolis that took most of initial practice to fix left AXR on the backfoot all weekend before recovering to fourth.
"Maybe the end results have been reasonably consistent, but it feels – and I’m sure everyone is the same – like we’ve left a lot of points on the table in quite a few races," Sims told Autosport.
"I’m somewhat surprised honestly that we are leading the championship going into the last round, but I think it’s probably just the reality for most if not all of us up and down the pitlane with the new cars that we just haven’t been able to execute a good solid weekend every time.
"Some of those errors or mistakes are down to us, sometimes it’s just been unfortunate racing scenarios.
"We’ve all had our issues through the year, and it seems like we’ve come out the other side of those in a slightly better position than the others so far."
Sims will rejoin Corvette Racing next year to race the new Z06 GT3.R in IMSA's GTD Pro class and said signing off on his season with AXR with the title "would be phenomenal and honestly right up there with the biggest achievements of my career".
However, he recognises the tight nature of the competition, with the top four crews in the championship split by just 38 points, means nothing can be taken for granted in what is effectively a winner-takes all scenario.
"Obviously it can all change, even with just one round to go, because the points are so incredibly close that positions in the championship can swing quite dramatically in the last race," he said.
"But I would have taken a lead going into the last race even if it was by a minute margin if we looked at things at the start of the year.
"It would be pretty amazing but it’s a big task still, don’t get me wrong.
"We’ve got the Porsches that are in very good form at the moment and the Acura is fast, we’ve had decent results during the season but I think it’s anyone’s to win because IMSA racing is like that."
