Used and amused: £70k BMW M3 CSL vs McLaren 12C

Typically, Thorney deals with 12C geometry that’s easily knocked out of alignment, or wear items like upper arms, lower arms and Z-bar links. There are, of course, horror stories, including gearbox failure related to input shaft issues. McLaren replaces the gearbox for £27k, but Thorney has developed its own driveshaft seals, input seals and bearings and, says Thorne, “we can now repair any gearbox around the world for £7500”. Cam phasers are prone to wearing, especially if engines are revved hard before fluids are warmed or run low on oil. That’s a top-end rebuild for £10k. So, yes, 12C ownership can be ruinous if things go really wrong.

But Thorney charges £95 per hour plus VAT and servicing should average around £1500 annually over three years – about £500 for a small service, £2500 for biggies. Thorney also offers warranties for £2850 annually to isolate owners from unexpected shocks.

When you go to drive the 12C, its fine breeding is immediately apparent: you lift a dihedral door, step over a chunk of carbonfibre tub and sit down with backside lower than knees and fantastic visibility through a widescreen windscreen. Press the starter and the twin-turbocharged V8 rouses with its belchy industrial monotone – lacking exoticism perhaps, but now a telltale McLaren signature.

Unusually delicate steering makes this potentially intimidating car feel surprisingly benign – slower and more natural than a Ferrari 458’s, and significantly more feelsome than both it and even the 720S. The ride quality also stands out, soaking up imperfections while taking nothing from this car’s eagerness to carve through corners. It feels low, wide and on the nose, with a striking lack of mass over the front axle. Despite McLaren’s march of progress, a 12C remains fearsomely rapid. The first cars had 592bhp and 443lb ft, but all were offered the 616bhp upgrade soon after (with the same torque rating), which, I think, also smoothed out a sometimes shunty delivery. There’s still lag to a significant 3500rpm or so, but it kicks hard enough thereafter to get the rear tyres spinning and feels downright furious at 7000rpm. There’s no question that this feels a pure-bred supercar, something that parking it alongside a BMW – even a very special one – only highlights.

While Thorney is more associated with M3 race cars, it does maintain road cars and probably sees a CSL every three months. Although it is based on the regular E46 M3, the CSL driving experience is amped up by significant detail changes: spot them by the unique 19in wheels, new front bumper, carbonfibre roof and ducktail bootlid; feel them by 110 fewer kilograms, the revised chassis and a 3.2-litre straight six bumped 17bhp to 355bhp. You sit, of course, far higher than in the McLaren on bespoke fabric bucket seats, a reminder of the BMW’s proletariat origins. They tilt you slightly forwards – odd initially, but natural soon after.

If you’re fond of nit-picking, you’ll think the CSL has rubbed its head together with the entire class. It rides quite firmly at low speed, if far from teeth-clenchingly so, the automated manual gearbox can feel unbearably lumpy if you refuse to adapt (just lift like it’s a manual and avoid tight parking spaces) and the initial steering response seems lethargic after the McLaren (even if it is fitted with a faster rack than the regular E46’s).

But the CSL remains a fabulous drive, with the suspension feeling taut yet still elastic enough given just a little speed, and the gnarly mechanical edge of the automated manual climaxing with full-bore sledgehammer shifts that are key to the CSL character. This is also a beautifully balanced chassis, with crisp front-end bite and bags of traction, if still a resolutely rear-biased, exploitable edge.

At the core of it all is the S54 motor. It’s smooth, pretty quiet and not particularly potent at typical speeds (a CSL is actually a little lighter than a 12C, at 1385kg, but has 261bhp and 170lb ft less and serves both figures much higher up the rev range) but pin the throttle and there’s the most fabulous honk from the unique carbon airbox and white-hot fury as the rev needle winds to 7900rpm. It’s the old-school M experience, where you have to wring the car’s neck to truly key into its capabilities, and thus you feel all-consumed by the experience.

Thorne describes the E46 as the best race car chassis BMW has ever made, in large part because, he says, it was designed as a race car first and road car second. But he’s also under no illusion that the McLaren is in an entirely different league: whether it’s construction, handling, design and, above all, performance, the McLaren remains three times the machine.

The trade-off, naturally, is drastically reduced running costs. Thorney charges £75 per hour plus VAT labour for BMWs, and servicing alternates between Inspection 1 (£400-£600) and Inspection 2 (£500-£700). CSLs, Thorne says, are generally robust cars. The cracked boot floor issue so common to M3s oddly doesn’t afflict the CSL: Thorne has seen only one, but has repaired 30 regular M3s. Nor is the Vanos variable valve timing issue notorious of the previous, E36 model a problem.