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Training for the Nürburgring 24 Hours: behind the scenes

Last year, our own Jethro Bovingdon tackled the Nürburgring 24 Hours in a BMW M4 GT4. But first he had to reacquaint himself with the epic circuit, and get to grips with the car he’d be driving there...

It’s early April at the Nürburgring. BMW’s marketing department have hired the Nordschleife exclusively between the hours of 8am and 4.30pm and have their eyes on setting some impressive lap times. In a workshop nearby, the cars are being prepped. The priority is the new M2, but the M division feels that the M4 CSL and M5 CS have plenty of time left in them. Their previous runs were heavily compromised by patches of damp and a mulchy leaf cocktail. I would love to be a fly on the wall for this little adventure. Who doesn’t want to see how these Nürburgring lap times are achieved? Even those windbags who moan about the ‘relevance’ of the Ring. 

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Yet for all the excitement I’m in a darkened room, dreading opening the curtains. You see, whilst a road car lap time programme operates from one corner of the Nordschleife car park, I’ll be on the other side testing a new M4 GT4 in preparation for the 24-hour race held in late May. The forecast yesterday was pretty good. Ish. But having been away from this place for probably five years, the idea of trying to get heat into a set of wet tyres whilst remembering all the little tricks and foibles of this monster circuit sounds vaguely hellish. I can’t hear rain being slapped against the window. There’s even a little glow around the edges that suggests it can’t be that bad. 

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> Nürburgring 24 Hours 2024 to feature 130 car grid, including a Dacia Logan

In fact, it’s even better than that. Sunshine! Not a cloud to be seen. Can this really be? More good news: the jeans I hung over the balcony no longer stink of sizzling steak (any regular at the Ring knows to hang their jeans outside after a visit to the Pistenklause). What a start to the day! With the worry of rain extinguished all I need to concern myself with is being quick enough, not crashing, remembering all the controls on the steering wheel and, maybe, to enjoy myself. How hard can it be? 

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So, this is Day 1 of my re-introduction to the Nürburgring 24 Hours and my re-introduction to driving around this wild place in general. Well, technically it’s Day 2. Yesterday I met the outfit running this media car, the highly successful BMW Team RMG, and looked around their immaculate premises located around 30 minutes from Nürburg in a town called Andernach. Team RMG was founded in 2010 by Stefan Reinhold, who has extensive history working in F1 and GT racing. The operation was set up to partner BMW as it prepared to once again join the DTM championship in 2012.

After a successful stint in DTM, the team has now focused on GT racing and did a huge amount of development work on the new M4 GT3 and ‘my’ car, the GT4. The trophy cabinets are bursting and empty champagne bottles line the entirety of the mezzanine structure above the workshop floor. We are shown videos and data from their GT3 drivers at certain key points and encouraged to try the simulator. It feels very serious. At this stage I just want to remember when the bloody track goes left and right. Even my teammate, Christian Gebhardt, the man who sets the Nordschleife times for Sport Auto’s Supertests and completes hundreds of laps per season, chuckles when we see how Dan Harper makes up a tenth of a second through Hatzenbach. 

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Christian and I will be joined by Auto Bild journalist Guido Naumann (also very quick and a former teammate of mine in a bog-standard Fiat 500 at the N24. We qualified 180th and dead last. However, we did beat the Prodrive DBRS9 in the race itself on our way to a glorious 148th-place finish) and BMW M’s project manager of driving dynamics, Jörg Weidinger. That means his day job is creating cars like the M5 CS. No wonder Jörg is always smiling and it explains how he’s quite so handy around this place. Today, he’s here to shakedown the GT4 and will be the man tasked with attempting the aforementioned lap records in the M2, M4 CSL and M5 CS. We have also set aside double stints in the night for him if it’s pouring with rain. You’re welcome, Jörg!

The rain has stayed away but it is freezing. Literally. I scrape ice from evo’s Fast Fleet M5 CS before meeting Team RMG and the rest of the guys, and the track itself is lined by deeply frosted grass and Armco glistening with icy crystals. The plan is pretty simple. Jörg will do a couple of shakedown laps, then Christian will do an out lap, a flyer and an in lap. I’ll go next, repeating the cycle, and then it’s Guido’s turn. Should all go according to plan we’ll then each get an eight-lap race-stint simulation. The N24 runs the Nordschleife in combination with the new GP track, but today we’ll just worry about the big beast. The new circuit is a place to grab a breather in the race itself, so if we can get comfortable on the real Nürburgring we’ll be in a good position come race weekend. 

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Those first few laps are tentative. It really is cold and slippery and we’re running a hard Pirelli slick. The GT4 is an awesome thing. Due to Balance of Performance regulations it doesn’t have anything like the punch of the road-going M4, but the sheer stability is confidence inspiring. It feels light, direct and very positive, but there’s no nerviness at all. The only real shock is remembering how physical it is to drive around this track at anything approaching racing speeds. The surface drags you in all sorts of directions, the kerbs are vicious and speeds are so high that everything feels critical. There’s literally no time to rest. 

The GT4 class has really evolved quickly, too. Corner speeds, even in these low temperatures and on a very durable slick, are extremely high. Where early GT4 cars looked like road cars that had been lowered a few millimetres and then decorated with a rather apologetic rear wing, the newest of the breed look like mini-GT3 racers. Flicks and louvres, big swan-neck wings, steering wheel with the complexity of a Le Mans prototype’s (well, maybe not but I like to think so) and an aura of toughness that only endurance cars possess. 

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Wringing everything the GT4 has to offer takes many, many deep breaths, quite a few expletives and a level of commitment that feels slightly deranged around this track. Lap times? Quicker than an M4 CSL (7:15.67). And it will do that all day and all night. At least that’s the plan. Lapping the M4 GT4 on an empty Nordschleife for a full stint is exhausting and an extreme challenge for a layman like me. To double stint in the dead of night with 160 other cars scraping splitters, bouncing over kerbs, kicking-up dust and grass and sometimes shedding bodywork on barriers and dripping fluids just where you don’t want them? That’s the magic of the N24. Hope I can still handle it.

BMW M4 GT4: in detail

Engine 

The M4 GT4 retains the 2993cc, twin-turbocharged straight-six ‘S58B30’ engine from the road-going M4, with up to 542bhp and 479lb ft of torque available, as per the M4 CSL. However, the GT4’s ECU can be manipulated to comply with Balance of Performance requirements at different championships. This isn’t a simple reduction in boost, and hence power, in every gear; instead the restriction might just be in gears one to four, for example.

Gearbox

Some GT4 cars now run full race sequential gearboxes with pneumatic shift, but the M4 GT4 sticks with the road car’s ZF auto, albeit with seven ratios instead of eight and a new motorsport program for faster shifts. It can still be used as a full automatic or operated with the paddles. In place of the fully variable M Differential there’s a Drexler limited-slip diff. There’s also a launch control function but this won’t be any use in the N24, which has a rolling start. 

Driver aids

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Many of the features of the M4 road cars remain in the GT4, although with unique programming for the higher forces delivered by race suspension and slick tyres. There’s a full DSC mode (good for wet weather but also useable in the dry), plus MDM mode, which still utilises the stability control. The driver can also elect to disable ESC and instead use the variable traction control system, which has ten settings. On a very cold test day, MDM felt very good indeed.

Lightweighting

BMW has collaborated with sustainable lightweighting experts Bcomp on the GT4, replacing carbonfibre components with new items incorporating natural flax fibres. Bcomp’s AmpliTex and PowerRibs products are used extensively for the interior, plus externally in the front splitter, bonnet, doors, bootlid and adjustable rear wing. The weaves look more like early carbon-Kevlar and F40 geeks would be pleased to see the patterns beneath the paint and decals. Safety is also improved as the flax-fibre fabrics don’t splinter upon impact. 

Suspension

KW supplies the two-way-adjustable motorsport dampers for the M4 GT4, with three options for springs from H&R. The dampers’ solid-piston design enables greater control of the hydraulic forces than a conventional damper. Anti-roll bars front and rear have five positions to help further tailor the balance and body control. 

This story was first featured in evo issue 310.

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