The 25 Hours of Thunderhill has become something of an outsized version of its former self. What began in the early 1990s as an amateur three-, six-and 12-hour event has transformed to what could be considered a 25-hour pro-am event.

It has been a gradual but undeniable transition over the years. In the early years, the majority of teams used the venerable Mazda Miata and the BMW E30. Those teams always brought lots of spares, but then they graduated to bring entire spare cars. The “arms race” led to advances in car-to-pits telemetry and real-time data transfer.

The escalation continued apace when teams really started gunning for the overall win, because the 25 Hours of Thunderhill was beginning to attract teams from all over the world. Winning the 25 Hours of Thunderhill really means something, so teams started showing up with factory built Porsche Cup cars. In fact, the Porsche 911 is still the chassis with the most overall wins at the 25.

Of course, change is a constant, and now the influx of prototypes and sports racers are beginning to change the face of the race again. The hardware that teams are bringing includes cars built by Ligier, Ginetta, Praga, Radical, and Norma. And, yes, some teams are even bringing two of those to have on hand for spare parts.

The interesting thing, and maybe what makes this race so challenging, is that those upmarket prototypes can only win if they can navigate a field of slower, production-based cars, many of which are homebuilt and campaigned by plucky amateur teams. Lap time deltas of up to 25 seconds are now common, which means that the fastest cars are passing the slowest cars every few laps. You don’t get that at either of the 24 hour races in Daytona or LeMans, or even a 12-hour at Sebring.

That added challenge is part of what makes a win at the 25 so special, and most assuredly what makes it difficult and so elusive.

To find out more about the origins of the race, we got hold of Jerry Kunzman who has been to every one of them since the beginning. He’s never raced in the event, but he’s seen it all. Why 25? Kunzman explains that — and a lot more — below.

NASA co-founder and NorCal Regional Director Jerry Kunzman.

Q: We heard the origins of the 25 stemmed from nothing more than staging a race at a time of year when the track wasn’t very busy. Can you describe how this whole thing got started?

A: It started in the early 90s. Back then, track dates were hard to come by. We accepted the first weekend of December for an event, because weekends during that time of year weren’t as popular, and so it was what the track could spare. We hosted the first NASA endurance, three hours at length. For about two to three years, that race held the first weekend of December, taking us into the late 1990s.

Q: How many years was it six hours and when did it go to 12 hours?

A: We went to six hours, probably in about 1995. Then in 1998 we picked up Timex as a sponsor, but they only agreed to a 12-hour race. We did that for five years (1998 – 2002). To go back to the first question, it turned out that this was an ideal time of the year. All entries were racers from regular classes during the year. Once the season is over, they could then “take a chance” on breaking or crashing their car.

Q: When did it go from 12 to 25, and why 25 instead of 24?

A: Immediately following the checkered flag of the 1999 12-hour, I looked at NASA co-founder, Ali Arsham, and said, “I don’t know about you, but I could easily do this for another 12 hours!” He agreed. It seemed easy … at least at the time. From that time on, we always knew we’d turn the event into a 24-hour race. The only question was when.

We had an awards banquet after the 12-hour, hosted at a restaurant in Willows. During the 2002 awards banquet, on my way to the podium — and after a few drinks — I just decided to announce, “Next year will be a 24-hour race!” But a second later, I laughed to myself as I thought, “24? Why not 25?” So, without telling anyone, and without consulting the track, I announced that, “Next year, this race will be 25 hours long!” An immediate round of cheers and applause broke out. It was then I thought, “Maybe I should have asked the track first?”

Thunderhill Raceway CEO David Vodden and Jerry Kunzman.

Q: What were some of the more surprising things you have seen at the 25?

A: Several things. First of all there’s always a stock car team that is most entertaining. Between spinning on a parade lap, shenanigans in the pits, and all the other rules they tried to break, we — the race officials — have had a never-ending source of entertainment. We probably should have just “uninvited them” to future events, but we’d really miss their antics.

We’ve had some pretty bad crashes, and we learned from them. This race, between darkness, mud, gravel, rocks, and a myriad of other things, brings up all kinds of issues never thought of before.

Q: How much of a role do you think the weather has played in the challenge and mystique of the race?

A: I personally haven’t driven in the event, or been part of a team, so all I can do is give you some observations. First, we’ve been seeing very good weather far more than harsh weather. Typically, it’s T-shirt weather in daylight hours and perhaps low 50s during the night. Even when it gets into the 40s, it’s tolerable with proper clothing, of course.

However, we have had just about every kind of unpleasant weather one can think of. We’ve had rain, snow, hail, freezing temperatures, high winds, and fog. On two occasions over almost 20 years, the fog was bad enough to cause a delay. Teams do have to plan for all contingencies, because you never know, especially with “microclimates.” Crewmembers can be wet and hands so cold, it becomes a challenge just to work. Undesirable weather is definitely a huge factor. It’s just the quantity that determines difficulty.

Q: Why do you think the 25 has achieved the level of notoriety that it has over the years?

A: Well, on one hand, I am a little surprised that there’s not more notoriety, but people really enjoy people stories, adversity, and challenges. There’s a tremendous amount of that that goes on. But without an in-depth television series, it’s hard to get fans to understand the massive challenges on every level. On the other hand, I am humbled and grateful that this, “little Nor Cal event,” is as cool and as big as it is now. I have no complaints!

Q: Who were some of the most famous pro drivers to race the 25?

A: Patrick Dempsey was registered one year, but I can’t confirm he ever showed up. Bryan Herta (IndyCar), Al Unser Jr. and Al Unser III, one Andretti, I think, Kurt Bush (NASCAR), Lynn St. James, Boris Said, Jean Alesi (F1), Simon Pagenaud, Randy Pobst, Greg Pickett (Trans Am), and a number of others.

Q: Why do you think those big-name drivers compete in the 25?

A: I am not sure. But I’d bet they heard of the fun-factor, so much more than other races.

Q: What do you hope to see at this year’s 25?

A: I can hope, and I can dream, but being realistic, my biggest hope is to have the most exciting racing. This is race is ripe for those with great tactics and strategy in an ever-changing environment. In terms of drivers, I’d like to see the growth of the club racer as well as some super stars from the pro racing world.

Image courtesy of Jerry Kunzman


    • You’re right. In the 1990s, I heard some people say, “hey that’s Donny Edwards,” and they were from New York. We broadcast all races back then on the Bay Area Sports channel, but it also went out on satellite, where these people saw him from their homes in NY. Everyone knows, Donny is an integral and entertaining part of the NASA family!

  1. Team Prototype Development Group has had legendary pro racers Davy Jones and Elliot Forbes Robinson driving the Factory Five Racing GTM in the 25 Hours of Thunderhill event in years past.

  2. Great event. I helped officiate one year and was asked to have a conversation with a competitor about a penalty after contact on course, He came to the tower with a case of whiskey ‘as a donation’. He was very disappointed to learn I don’t drink.

  3. Great event. Truly an endurance test on many fronts. So glad I got to run it several times and host it at Thunderhill Park. Could turn out to be our legacy Jerry if it continues to grow and attract global attention. Who else would have just done such a thing? “Two wild and crazy guys,” I suppose.

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