The Highs and Lows of the 25 Hours of Thunderhill

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Words by Mike Bonanni (Yost Autosport Driver)
Photos by BC Racing North America

The 25 Hours of Thunderhill; North America’s longest endurance race is no joke. Yost Autosport team principle Jordan Yost has always said “You have to know in January that you’re going to race the 25 Hour in order to have any chance at making it.” The race itself takes place the first week of December every year at Thunderhill Raceway Park in Northern California. Its cold and most years the race is thrown a curve ball from Mother Nature whether it be rain, fog, or both. The range of machinery spans from Spec Miatas and 100 horsepower Honda Fits all the way to factory GT3 spec race cars and top level prototypes providing an incredibly interesting race to not only watch, but be a part of, completely different from any other endurance race out there. Just finishing this race is something almost half of this year’s 65 car field didn’t accomplish.

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For Yost Autosport, it was our second consecutive year competing in the 25 Hours of Thunderhill. In 2014 the 25 Hour was the first race for our newly built BMW M3 race car and we are proud to say that in our first time out we finished the race. Now that completing the race was under our belt we came into the 2015 event with the goal of being competitive. The M3 received a complete teardown and rebuild after the 2014 25 Hour and we proceeded to race it in three other, shorter, endurance races throughout the year finishing on the podium in two of the three, winning our last event going into the 25 Hour. Confidence was high going back to this race with a much faster car and a lot more working knowledge learned from our first season of endurance racing.

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The team arrived Wednesday and spent the entire day setting up our pit area to create a comfortable and functional space for the team to remain comfortable and at the ready for 25 hours straight come race time. Thursday was spent double checking all major components of the car and by Friday it was finally time to hit the track. Practice was being run all day long with qualifying for the race scheduled just after nightfall. The weather was overcast with thick gray low hanging clouds covering the circuit, a contributing factor to our first problem of the weekend; our car was too loud. It may sound silly as race cars are generally very loud but this particular track and event have a maximum sound limit of 95db measured at 50 feet. This is a problem we did not have last year when the weather was much clearer. Overcast weather causes the sound waves to bounce off the low slung clouds and amplify. The track’s procedure when a car is too loud is to pull them off-track and let them back out after making modifications to quiet the car. We had come prepared with alternate exhaust tips that angle away from the side of the track where the microphone sits, a common fix among racers. This doesn’t actually make the car any quieter it just re-directs the sound but as long as the trackside microphone reads below the maximum limit the track doesn’t care. Unfortunately for us, it wasn’t enough and we were still too loud. We spent the entire day coming in, trying some sort of fix, going back out and failing each time. While a team member drove hours across different towns searching for universal mufflers we could install for an actual fix, our goal at the track was to find any temporary solution that would allow us to run at least a few laps of qualifying.

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When qualifying came around it was dark, and the first time any of the competitors got the chance to drive at night during the race weekend. I was in the car to qualify and this particular event has a very unique set of challenges for qualifying. One, it’s the only race that qualifies in the dark and it’s the first time people get to see if whatever light setup their car is equipped with actually works. Lighting at night was a major problem for us at last year’s race; we just simply underestimated what we actually needed. We learned from that and through three other night races this year developed a new light package that was far and above what we ran a year ago. Others on the track weren’t so fortunate and a lot of cars slowed their pace way down in the night simply because they couldn’t see and with 65 cars total on track at once, it’s virtually impossible to get an entire lap in without running into traffic. Such was the case for me in qualifying and unfortunately I couldn’t get a clean enough lap to match our practice times. Regardless I qualified the car 22nd overall, not what we were hoping for but we had 25 hours of racing to make up the difference.

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During qualifying our team member came back to the track with two gigantic glass-pack mufflers to hopefully fix our sound limit problem permanently for the race. The only problem was they didn’t quite fit nicely into our current exhaust setup and our only option was to have them stick out from the rear of the car about 8” past the body work. We added more turn-away tips as added insurance since we wouldn’t be able to test the new setup before the race. Fortunately for us our new exhaust setup, affectionately nicknamed “the chili peppers” did the trick and we ran the race without issue.

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The race itself started at 11:00am on Saturday preceding a big opening ceremony complete with military fly-over and all the cars and teams lined up on the front straight for the crowd to walk and check out, a very cool feature of this race for fans and teams alike. Jordan Yost was the driver in the car for the start of the race and was set to start from the outside of row 11. When the green flag dropped Jordan quickly made up a few positions and settled into a groove for his first of many hour long stints behind the wheel. During the first pit stop we got Barry Yost in the car for the first of his stints, followed by yours truly for hour three of the race. Once we all got a stint under our belts it was time to put Barry back in the car for a 2-hour double stint to bring us to sundown and the start of 14 hours of night racing. Jordan and I went back and forth each doing double-stints late into the night stopping every hour for fuel and every 3-4 hours for a new set of Achilles GS-328 race tires. I was in the car at 11:00pm when on the windshield, rain started to appear. Within two laps the rubbered up track was far too slippery and wet for racing slicks and we had to come in to the pits for our wet weather tires, the Achilles 123S street tire.

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We were excited to see that in the tricky wet and dark conditions our Achilles tires and new lighting setup brought us right to being one of the fastest cars on track. We were making up tons of ground on our competition and quickly climbing up the ranks. The rain was acting as unpredictable as it possibly could have been. Just as you were starting to see a dry line appear a little drizzle would start and make you question whether or not it’s the right time to make the move back to the slick race tires. By the end of my double-stint there was a definite dry line and since we were coming in for a driver change and fuel anyway we decided to send Jordan back out on slicks. This proved to be the correct move as he was immediately back to our normal dry pace. Halfway through his double stint the rain came back and Jordan was back in for another tire change back to the wets. Just as he got sent back out the skies opened up turning to torrential conditions that slowed the entire field down to a crawl. Fortunately it didn’t last too long and I was able to get back in the car at the tail end of the heavy rain. From that point forward the rain would stay consistent and the track remained wet for the remainder of the race.

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At this point it was around 6:00am and I was back in the car most of the way through another double-stint. We had officially broken into the top 10 overall and the next three positions were just a few cars ahead. We were circling around behind the pace car while the safety crews cleared two more wrecked cars (a common theme during the challenging wet/dark conditions) when I started to notice a clunking noise coming from the right front of the car. I reported back to the pits and since I was just about 20 minutes from coming in for a scheduled pit stop our plan was to inspect the right front during that stop. The car felt normal so I was completely okay with that. That’s when fate intervened and fogged up the inside of the windshield so badly that I could no longer safely navigate. I was simply following the tail lights in front of me and there was no way I could re-start the race under these conditions so I had to bring the car into the pits immediately so the windshield could get cleared. I had to be guided back to our pit lane by a crew member shining a flashlight that I could follow, like a T-Rex. During the sooner than scheduled pit stop the crew wiped the windshield and inspected the right front where we found a random bolt that had vibrated loose over the course of now 19.5 hours of racing. Unfortunately the loose bolt was beating up against the external reservoir of one of our BC Racing ZR series coilovers weakening the area where it mounts to the shock itself. When the crew went to tighten the loose bolt the weakened link broke right off and shock oil spewed everywhere. Normally we have a spare set of coilovers on hand just in case one gets damaged, but unfortunately a mix-up with UPS losing our spare set left us high and dry. Right as the sun was coming up, 20 hours now into the race we had to call it quits…all because of a loose bolt on a part of the car where you would never expect to come loose. That right there is the nature of this race though. Best we can do is learn from it.

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The silver lining in this race however was the realization that we were indeed accomplishing exactly what we had set out to do. Our car was yet again running flawless and strong up until the point of failure and in the wet conditions we were incredibly fast. We were 10th overall when we pulled in for our final pit stop, well on pace to finish in the top 5 overall by the end of the race, a massive testament to our hard work and the amazing products we outfit our car with. Unfortunately the only thing we were denied was the chance to validate it.

We will be back stronger than ever in 2016 with a brand new car! The 2015 25 Hours of Thunderhill was the final race for our beloved E92 M3 under the Yost Autosport banner. It is up for sale to make way for a brand new BMW M4 that you will see at the 2016 25 Hours of Thunderhill!

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As for our BC Racing products, we could not be happier, as has been the case since day one with this car. In 2014 we proved that BC Racing Custom Coilovers were up to the task of completing a 25 hour long race with their proven ER series coilovers. This year, with the release of their triple-adjustable ZR series coilovers we were able to back up their reliability with the added benefit of more fine-tuned adjustability. Our original set of ZR series coilovers made it through 15 hours of regular season racing and another 19.5 hours of this year’s 25 hour and they felt the exact same on our final lap as they did on our first.

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Our new BC Forged wheels did an amazing job as well! Prior to the release of BC Forged wheels we were having major failures and issues with other wheels and the BC Forged wheels not only look the part but are lighter and stronger than anything we’ve run before. It’s needless to say we are believers and will be Team BC Racing for life!

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