This article first appeared in the speedarticle Post in issue 001
Most of us car-folk are acutely aware of new trends and technologies that shape the current definition of the “sports car”. If you’re trying to shield your eyes from it all, there’s at least some sort of magazine, online thread, or ad, to spread the word. Between Koenigsegg’s routine use of captured alien technology, or BMW’s development of black-hole curb weights, we’re all generally aware of the current definition of the sports car.
However, there’s an automotive system that’s evolved under-the-radar. A system that’s received near zero attention from enthusiasts and media outlets, not even appearing as a blip on the nerdiest of forums. This engineering hallmark stands as the gatekeeper - hoisting certain models and brands into the tuning and Nurburgring limelight, or without it - banishing them to the realm of just old but gold. This collection of parts has single-handedly changed the definition of the sportscar over the last 30 years, and it’s probably the reason Your Dad Can’t Drift.
Over time, these components have turned widow makers into playful learning machines, trickling down into everyday sedans, too. I’m talking about rear multi-link suspension - meaning any rear suspension with three or more control arms for each wheel.
Before we get too into-the-weeds, I want you to think about your favorite production car. Whether it was in a YouTube video or you saw or one on the road, I can almost guarantee that if it’s older than around 1995, you’ve never really seen one in a continuous powerslide, at least not without a 100-meter wide runway and a certain Ben Collins behind the wheel. So, maybe your dad actually can drift, but outside of the occasional snow-flurry, he’s not familiar with comfortably playing around on the limit of grip. He’s had cars with more power than you, fewer driving aids, skinnier tires, bigger displacements, more torque, but still - there’s just no talk of winding off the lock like Chris Harris, or even wanting to be able to wind off the lock like Chris Harris.
Let’s dive into the engineering decisions that define this characteristic of the contemporary sportscar, and why it’s something you really want if you love driving.
Most European cars built before the mid-90s featured a layout known as “trailing arm” rear suspension. And when I say before the mid 90s, I mean just about every premium passenger car from the Hindenburg disaster through to the dot-com bubble. This is different from the “live-axle” used on older American cars, trucks, and industrial vehicles, too. Trailing arm cars usually feature a single large control arm per rear wheel. The rear wheel hub is fixed to this arm, and the entire arm pivots on one or two bushings placed forward of the rear wheel. Trailing arms are typically triangular in shape when looking up at the bottom of the car (on a lift), although in the case of Porsche, they’re often referred to as “Banana” arms, stretching out to the rear wheels from the center of the car, forming a slight arc along their path.
Even early 2000s trailing arm setups often do not feature any form of camber or toe adjustment in the rear. (Z3M Coupe I’m looking at you). Trailing-arm suspension tuning often requires significant fabrication, and the result will usually end up negatively impacting something else - such as unintentionally stretching the wheelbase or having extremely limited wheel travel. Oftentimes, the best way to make these trailing arm setups work is damage control - flat-out limiting their total range of motion. In racing, manufacturers will do everything they can to modify these setups to beat them into submission. The rowdiest E30 M3 DTM cars featured arms that looked like Frankenstein's monster, chopped up, heim-jointed, boxed-in, fully hot-rodded. And as tires have evolved from donuts, to squared-off, to ultra-wide aspect-ratios, the lack of precision a trailing arm provides has become the handling bottle-neck.
In a corner coupled with squishy body roll, a trailing arm sets up the outside tire square with the road as the car leans over. Added toe-in on the outside tire fights the loss of grip from the inside tire while pushing the rear end towards the inside of the turn. This system is also compensating for the tire slip-angle - the slight difference between direction of travel and the direction of the tire. If we freeze time in the middle of the turn, things are mostly hunky-dory, the issue then begins with the dynamics when the car changes direction. As the toe dramatically changes with ride-height during weight-transfer, as well as the camber racing to catch up with the body roll, the tires aren’t being consistently loaded across their width relative to the weight transfer. This leads to a rear end that creates an artificially low limit, as the tires aren’t being optimized and kept perfectly in sync with the road and the weight transfer. Keep in mind that this is all theory - add some real-world bumps and surface changes to the mix, and you have several millimeters of toe-change and a couple degrees of camber-change going on unnecessarily while you’re trying to extract the most grip and set up for the next turn.
Mercedes saw this drawback of trailing arm suspension on the horizon, and in the 60s began development of a multi-link rear system on their (gorgeous) C111 prototype. This used 5 arms per rear wheel in a “semi-trailing arm” configuration, with 4 of the arms dedicated to camber and toe control. Beginning in 1984, Mercedes would go on to ditch trailing arms entirely in favor of a true multi-link rear subframe with the debut of the W124 E-class. Trickling down from the executive W124, the baby-benz W201 190 sedans also received true multi-link in 1995 - just in case Mercedes hadn’t stepped on BMW’s toes hard enough.
The multi-link rear subframe in these Mercedes allowed ride quality to be plush - with gobs of suspension movement - while retaining handling precision with camber and toe being kept in check. In other words, a car with grip that is inert relative to its weight-transfer, giving it balanced and extremely predictable handling - now we’re getting somewhere.
In the case of BMW, this revolution was more of an evolution, with a semi-trailing arm configuration being adopted for the E36 3-series in 1992, ditching the E30s post-war trailing arm setup. BMW wisely kept costs down by using only 3 arms per side, with upper and lower arms setting the wheel camber, and the wheel bearing being affixed to a single-pivot point trailing arm. This was game changing for the ultimate driving machine, which was about to become the ultimate drifting machine. Come to think of it, I just saw that Adam LZ guy take on Formula D(rift) in his E36...
The E46 3-series rear system would be nearly identical to the E36 system, albeit with lighter, more cost effective, and as we now-know - more fragile construction. Now the M3 wasn’t just a great driver's car, it was a classroom. A few wrong moves wouldn't kill you thanks to the precision of the rear suspension. The car's progressive nature allowed owners to learn the limits and subsequently - learn performance driving and improve their skills. This opened up the pleasure of performance driving at the limit to a wider audience. This approach of cost-savings and suspension brilliance teed up BMW to create what would become the gold standard for rear suspension design in a passenger car, the E90 true multi-link rear subframe known internally as “HA5”.
Beginning production in 2005, this rear multi-link subframe from the E90 has been reinforced and widened to suit BMWs since. However the 5-arm architecture has remained exactly the same since 2005. Now, 20 years in the future, and even the 2025 M5 which weighs as much as a house and develops enough power to shred its 295mm wide rear tires, uses the same 5-arm rear suspension design.
While it’s not surprising that sedans from marques such as BMW have been incrementally sharpened for skidding around, the real winners from the multi-link paradigm shift are those which historically had the shadiest dynamics - cars which have had modern levels of horsepower the longest. The Porsche 911’s engine layout is near the worst-case scenario for a trailing arm configuration, and the combination of this weight distribution and banana-arms earned the 911 its widow-maker reputation. However, since the 993 generation, Porsche’s own multi-link suspension has been refined to bend physics, now allowing professional drivers and YouTubers-alike to slide 991s and 992s, dancing on the limit of grip with the motor out-back. The Ford Mustang shares a similar story - albeit fashionably late, adopting multi-link suspension in 2015.
So sure, Your Dad Can’t Drift, but next time your showing him a video of a car slithering about, or righteously leaving a car meet - probably something from the mid-90s and up - remember that it’s not just horsepower, tires, stickers, or balls, that are keeping it from shaming its owner. The multi-link rear suspension revolution transformed icons intended to flatter only the best drivers, into accessible driving machines for exploring the limit. That’s not to say there aren’t poor-driving multi-link cars, but you’re much more likely to get a second-chance in a vehicle with more than a couple of rear suspension bushings. And - probably more likely to make a big enough cloud of tire smoke to end up on the front page of more than a few people’s social media feeds.
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