NASCAR legend Jimmie Johnson has given a first insight into the Coronado Naval Base street course that drivers will encounter next month.

Johnson headed to his native San Diego on Monday to check out the preparations for the one-off race, and got to drive around most of the track in a car after having some test runs on a sim rig – sending some early warnings to teams about the surface.

Next month's race will be the seven-time Cup Series champion's penultimate entry in the series, having already announced his intention to hang up his helmet after next year's Daytona 500.

Johnson will actually run double duty at Coronado, having confirmed that he will enter just his second career Truck Series race – some 16 years after the first, when he stepped into a truck at Bristol.

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Johnson opens up on 'challenging' Coronado course

Johnson told the San Diego Union-Tribune: “It’s going to be a challenging course. The first thing I noticed today is how rough the surface is. There’s grit and bumps. It’s going to be hard on tire wear. The surface is going to be rough, even though they are repaving some areas.

“What I think the course leads to is a great show. It’s made for mistakes and passing. If you get it wrong and get offline, there are some big penalties to pay. But there are high-speed areas with tight chicanes that are very challenging.

“There are areas to pass. There are good acceleration zones out of the chicanes. And there are three good straights and one long straight. So, you’ll be able to pass. But if you get offline, you could have problems.”

Johnson 'never thought' NASCAR would race in San Diego

“I never thought there’d be a NASCAR race in San Diego. I never even dreamed of it. How could they answer the questions of where and how? Then I started hearing rumors.

"I still never thought a street course was possible. Then, when Naval Base Coronado was mentioned as a possible site, it clicked.

“What is exciting is to be able to go out as a driver with San Diego being one of my last two races.”

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