24h Karting Spa-Francorchamps: The Importance of Strategy in Rental Kart Endurance Races

So what do you need to successfully compete in Rental Kart Endurance Races? Obviously a couple of fast drivers that can consistently get fast laps in and can do long stints without loosing focus. And depending on the duration and number of kart changes, likely some luck with the karts (or at least avoid bad luck). And then there is the strategy around pitstops, which can easily become a win or lose factor and becomes all the more important for longer races with a low amount of mandatory pitstops, especially when those pitstops do not have a minimum time limit.

Case in point: 24h Spa Francorchamps. The rules only mention 7 mandatory kart changes and 1 mandatory technical stop. Obviously, there are extra pitstops needed for re-fueling (minimum of 9) which brings the minimum number of pitstops to complete the race to 17. None of these pitstops have an end-2-end minimum time limit as is common these days for many other endurance races. There is a timer to control the minimum time taken by the actual kart change, but that timer does not cover getting into the pits, getting weighted, driver change and getting to the kart change area.  The one technical stop has a timer set to 4 mins 30 secs but again does not include getting into the pits, getting weighted and getting to the technical stop area.

Looking at the timing results from the 2023 edition of the 24h Spa shows some amazing differences between the length of the pitstops taken by the top teams compared to what our team managed to accomplish. And I’m not talking about a 2-3 secs difference either.  The winning team Hola Lulu Racing managed to perform their kart changes (including driver change) in an average of 1 min 40 secs.  Our team KM Juniors spent an average of 2 min 4 secs.  That’s 24 secs per kart change multiplied by 7 kart changes, which comes out to a whopping 168 secs or almost 3 full laps!!!  Some other Rookie teams had pitstop times similar to ours, so it wasn’t just our team that lost time.

Even worse is the difference in the 9 re-fueling pitstops: as a rookie team we decided to perform a driver change during each re-fueling stop (so stints where about 90 minutes) which added extra time for the driver change but if a driver loses focus or gets tired doing double stints you lose the benefit of a shorter pitstop anyway.  Obviously, the top teams were able to do double stints of 3 hours so did not perform a driver change during re-fueling.  Still Hola Lulu Racing took an average of 49 secs for their re-fueling stops while ours took an average of 1 min 24 secs. Even subtracting 10-15 secs for the extra driver change, that is still a HUGE difference.  Losing a whopping 35 secs each time multiplied by 9 re-fueling pitstops comes out to 315 secs or more than 5 laps…  If we compensate for the extra driver changes, we still lost 20 secs per pitstop or 3 extra laps…

So where did we lose all that time? After reviewing footage as well as having a detailed look at the pitstop area at the Spa track, the answer is pretty simple: pitlane maximum speed. The rules clearly state the maximum speed in the pitlane is 18 km/h. The total length from the very start of the pitlane to the re-fuel/kart change area is ~140 meter. If you drive that entire length at exactly 18 km/h it would take you 28 secs. If you slow down too much and drive through the pitlane at a leisurely 10 km/h it will take you 50 secs or an extra 22 secs!!!  If you drive just a little bit over the speed limit at 20 km/h you will gain 3 secs. Really taking your chances and driving 25 km/h gains you almost an extra 8 secs.  Just in case you’re wondering:  yes, there was somebody checking speed through the pitlane with a speed gun. But slightly exceeding the speed limit resulted in a warning, so I’m sure top teams were playing with the limits…   As a Rookie team we were too focused on not breaking any rules to avoid penalties (a drive-through for speeding) but considering the above it is likely more beneficial to take your chances and slightly exceed the speed limit each pitstop and maybe get a drive-though penalty once per 24h…

Another big learning from our first experience at the 24h Spa: since you’re bound to get 1 or 2 ‘bad’ karts it is crucial to assign a driver to those karts that can best handle a ‘bad’ kart. Obviously, your instinct might tell you that you should assign your best drivers to the better karts so they can set good consistent lap times and gain places. But the fact is that when you pair a less experienced driver with a bad kart, they will not be able to drive consistent lap times and they’ll end up loosing so much time that it can’t be compensated by what your best drivers achieved in the good karts.  If there is one thing that distinguishes the top drivers from the rest is that they can still get a decent result when they get assigned a bad kart.  Most experienced drivers can get a decent lap time out of a good kart.  And since in a race like 24h Spa you’re stuck with a ‘bad’ kart for 3 hours, loosing an extra 1-2 secs per lap because the driver cannot handle the kart properly, really takes you out of contention.  

Unfortunately, our team experienced that issue: after climbing up to P20-P25 we got a really bad kart and unfortunately the next driver in line was one of our younger drivers. Even considering the kart had serious issues (we had to come in twice for 2 different repairs and lost 10 minutes just for those) his average lap time was still 1 to 1.5 secs slower than what the team that had the kart just before us were able to get out of it on average. So if we had put our best driver in that kart we likely had not lost that extra 1 – 1.5 secs per lap which considering we had that kart for 3 hours, would have avoided us loosing another 3 laps, even when considering the younger driver would have been a bit slower in a good kart as well.

One other thing we've learned the hard way: unless the kart really brakes down (engine fail, flat tire, etc...), coming in for maintenance on the kart is likely just going to make you lose more time. We came in for mainteance at the end of qualifying: no improvement. Then when we got the bad kart on Sunday morning we decided to come in because average lap times were off about 2 secs. Lost 6 minutes changing one of the engines. Result: no real improvement. Later on we came in again to fix the steering (loose bolt). Lost 4 minutes. Again: no real improvement in lap times. What we should have done instead is change the driver to a faster/more experienced one to limit the time we lost with this bad kart.

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So if you take all these learning and apply them to our final result:

1) Faster pitstops:  - 8 laps

2) Put faster driver in bad kart: - 3 laps

3) No kart mainteance unless kart really brakes down - 10 laps

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Current result:  P35 – 37 laps down

New result:  P10 – 16 laps down

That would have been P10 overall and P2 in the Rookie Class !!!  Obviously other teams also had their share of issues so it is always easy to say what should have been done in hindsight but it does show how much strategy calls can make a difference in these kind of endurance races.

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Obviously there are many other tips and tricks that can help. For instance you can gain time by re-fueling under FYC / Safety car but to do that effectively you need to:  1) be within the time gap where you can get to the next kart change without an extra re-fueling stop.  2) come in as soon as the FYC / Safety car starts, as many other teams will have the same idea and you might end up having to wait in a queue to get re-fueled. This requires constant monitoring of the race by the team manager so he/she can quickly tell the driver to pit.   This also goes for wet conditions, especially if there is just a big shower after which the track dries up again.  Pitting during the wettest part can gain you quite some time if timed properly.

Unfortunately we're not participating in the 24h Spa 2024 but I hope someone can use the above knowledge from our first participation to get a better result. CU at the track.