King In The Corners - Which style of bike is best in the bends?

Conventional wisdom would say the best bike on a racetrack – or at going round corners on tarmac – is a sportsbike. And, certainly in terms of lap times, that would make intuitive sense – after all, there’s a reason sportsbikes are also called race replicas. Over the years a lot of development has gone into making road-legal sportsbikes look, sound, go, stop and handle just like race bikes. In fact production-based racing blurs the line between road and track so successfully, Yamaha MotoGP rider Maverick Viñales, riding pretty much a stock, road legal R1-M, was faster at last year’s Portimao tests than five-times world champion Jorge Lorenzo on a 2019-spec MotoGP M1. Tidy.

And that’s why sportbikes have the frame, suspension and brake specs, steering geometry, weight balance, ground clearance, engine performance, electronic aids and riding positions they do. And also why adventure bikes don’t win races. At least, on tarmac.

But what about if, instead of focussing solely on lap times we also drill down a bit into the act of cornering itself. If we take a variety of styles of bike – three-wheeler commuter, retro, adventure bike, mid-capacity all-rounder and hyper-naked – can we zoom into their behaviour in the bends and identify hidden strengths that are overshadowed by sportsbike hubris?

And, as a broader point, does the style of bike we ride influence the way we go round corners?

Bennetts Bikesocial is going to find out.

To help us do this, we’ve assembled a collection of metal, wires, humans and gaffer-tape at Bedford Autodrome, near, er, Bedford.

The metal is a broad representation of the most popular styles of bike:

Suzuki’s GSX-R1000R is a great representation of the litre sportsbike class; a well-developed, well-rounded, neutral handling and vice-free 198bhp inline four sports machine. Corners are what it does.

Ducati’s Streetfighter V4 S is peak hypernaked; not quite a Panigale V4 S with the fairing taken off and flat bars fitted, but 205bhp of V4 close. Will the flat bars offer better steering leverage and feel over the sportsbike?

Honda’s Africa Twin Adventure Sports sits in the adventure bike sweet spot, with a sophisticated chassis and wafty suspension married to a 100bhp parallel twin motor. Will the tall riding position and agile 21in front wheel deliver more pace in the corners?

Yamaha’s Tracer 7 is a ridiculously brilliant combination of loopy 72bhp 689cc parallel twin and a forgiving, easy-going chassis and riding position. Is it the perfect blend of performance, handling and ergonomics for maximum pleasure?

Royal Enfield’s Interceptor was the most popular retro of 2020, putting out 46bhp from its 648cc air-cooled parallel twin in a genuinely classic chassis and geometry set-up. Will its relatively benign power delivery and simple aesthetic give it the edge in bends?

Piaggio’s MP3 comes with an extra wheel at the front, offering extra cornering stability. With a 43bhp single cylinder and a twist ’n’ go transmission, will three wheels have more cornering nous than two?

To measure the subtleties of the bikes’ cornering abilities, we also need an expert datalogger and a track rider – so we’ve enlisted the help of Bob Gray and Bennetts BikeSocial’s Web Editor, Michael Mann.

Bob’s day job is being Dean Harrison’s crew chief; he’s also a technical author and an expert in chassis dynamics. Bob has brought with him a 2D datalogging device, as used in MotoGP, to plot the bikes’ dynamic behaviour.

Michael is an experienced track day rider, and routinely rides a wide variety of models. Today, his brief is to ride all the bikes to a given level of effort.

We’ve decided to focus on a few key areas of bike cornering behaviour in a few specific sections of the lap – the chicane (T1 and T2) and the hairpin (T4). They are:

• Lap times – not relevant other than to show which bike was quickest overall, for context. But still could be interesting...
• Top speed towards T1 – taken from the straight before the first turn into the chicane; it matters because it’s context for the bikes’ braking performance and subsequent corner speed.
• Braking distance and most speed scrubbed off – slightly inconsequential measurements but, again, helps provide context for the first corner apex speeds. The faster you’re going, the earlier you have to start braking.
• Peel-in distance before T1 – the distance between starting to turn and the apex of T1; shows confidence in steering.
• Braking force – measured in g. The harder you brake, the bigger the number.
• T4 minimum speed – the lowest speed reached in the hairpin. The higher the number, the better the bike in the corner
• Lean angle in T1 – the first apex of the chicane
• Lean angle in T2 – the mid-point, and biggest lean, of the chicane
• Lean angle rate of change between T1 and T2 – how agile or flickable the bike; how quickly it can transition from full lean left to full lean right.

Lap times

First surprise of the day and it’s the naked Ducati posting a better lap than the race rep Suzuki. But then maybe it’s not so surprising when you consider the Streetfighter is more powerful than the GSX-R, has better quality suspension and brakes, better electronics, is lighter, and is geared to produce more low-down acceleration. It also has the benefit of a more upright, less committed, flat-bar riding position – at a fairly short, point-and-squirt track like Bedford Autodrome’s southern circuit layout, that’s a combination the even sporty Suzuki just can’t match.

Next surprise is Honda’s lolloping Africa Twin lapping quicker than a Tracer 7 – admittedly, the Yamaha is giving away 28bhp to the adventure bike, but instinct would suggest the Honda’s 21" front wheel, top-heavy weight from its 24-litre tank and soft, long-travel suspension would tip the scales in favour of the lighter, conventionally-tyred Tracer. But it doesn’t.

No surprises at the back of the grid and the modestly-endowed classic and super-commuter. But the lap times set up what we’re hoping to discover – that just because a bike isn’t shaped and built like a race bike, it can still throw up a few surprises in the corners.

Top speed into T1

Top speeds run in order of horsepower and the corner exit onto the straight makes it a bit of a drag race. Given all the reasons listed above, it’s less of a surprise to see the Ducati beating the GSX-R on track top speed too – and Bedford’s straights just aren’t long enough for the better aerodynamics of the Suzuki to come into play. Worth noting the Ducati is almost twice as fast as the Piaggio.

Braking into T1

This is the distance between hitting the brakes and the T1 apex, the total speed scrubbed to the apex, and max brake force.

Michael is the last of the late brakers – for a different feature on the same day (see Eye Tracking). Michael was actually braking later on the Tracer than BSB runner-up Jason O’Hallaran. And we can clearly see he’s got more confidence in the Ducati’s front end and brakes than the Suzuki, braking later and from a higher speed than the GSX-R – partly down to better brakes, tyres and forks, but also possibly because of more confidence in the Ducati’s upright riding position under braking. Hard braking on naked superbikes that run sportsbike geometry, suspension and brake systems, but have flatter, higher bars and put the rider’s weight over the front end more, tend to give more weight transfer and feel more secure – as if they’re ‘pinning’ the forks into the tarmac from above.

But the Ducati and Suzuki are close – because 1.2g is pretty close to the limit of road tyres, road suspension and electronic intervention (MotoGP bikes at T3 at Red Bull Ring in Austria pull 1.5g – and that’s with carbon brakes, slicks and the best riders in the world on board!).

The Africa Twin brakes a good deal earlier than the Tracer, but that’s not just because it’s travelling faster. The Honda has a 6.6% higher top speed but needs 22% more distance to slow to the apex – this is where its extra weight, suspension travel and Michael’s confidence in the Honda’s 21” front come into play.

The Piaggio and the Royal Enfield are the opposite: The Interceptor is 20% faster than the MP3, but there’s only 8% difference in braking distance – suggesting Michael has a lot more confidence in the Enfield’s front end as he gets to his peel-in speed, but has more confidence in braking harder with the Piaggio’s pair of front wheels.

Chicane lean angles

At first sight this is a right old random mess of data. These are lean angles taken from the first and second apexes of the chicane, and the only definitive constant is the Piaggio, dragging its undercarriage and physically limiting cornering before the limits of grip from the front two tyres are reached. Maybe if the track was wet it’d be a different story, but in the dry there seems to be little case to be made for the extra security of two small wheels at the front of this particular wagon in terms of cornering joy.

Of the rest, the Tracer is probably showing its true colours best; a lightweight, flickable, funky machine with enough chassis nous and ground clearance to be capable of being properly Mann-handled about, but without the intimidation of either nearly 200bhp and 150mph potential, or the gangly worry of tall, soft suspension and a skinny front tyre. In many ways it’s an optimal bike in the chicane, allowing Michael to fully get the Tracer’s measure and maximise its potential. With a relatively low top speed it’s easier to estimate speed and set-up for the first part of the chicane.

The other outstanding number is the Ducati’s lean angle at the middle apex of the chicane – the rest of the figures are fairly close, within a few degrees, but the Streetfighter seems to have a significant edge as it maxes out in the middle apex. This is all about confidence in grip as much as steering, as the bike is picked up and pushed down inside one second. With a few more laps Michael might have got closer with the GSX-R, but then his numbers on the Ducati would also have improved. As a baseline control, it shows the Ducati has an out-of-the-box advantage.

With a whole 10° less angle on the Africa Twin – in T2 even the Interceptor beats the Honda – this is where skinnier dual purpose tyres really count against the adventure bike.

Angular rate of change in T1/T2

This is a measurement of flickability, for want of a better word – it’s the rate of change of lean angle between the apex at T1 and T2, or how quickly the bike can steer from full lean to full lean; the bigger the number, the quicker the bike rolls from left to right and vice-versa.

The number of degrees is a rate of angular change, not the actual degrees of change. So if a bike is stood upright and we let it fall on its side, it will rotate through 90° (along its roll axis). If it takes 1 second to fall over, then its angular rate is 90°/s (degrees per second). If it takes 0.5 seconds (because you pushed it over), the angular rate increases to 180°/s even though it’s still only rotating though 90°.

So in the Ducati’s case, lean angles in T1 and T2 are 33° and 46°, so in total the bike revolves through 79°. It took 0.94s to do it, hence the figure of 84°/s.

In terms of actual time, all the bikes go from full lean right to full lean left in just under a second.

Speed at apex T4

T4 is a V-shaped hairpin – tight in, opening out on the exit. Unlike the chicane, T4 exaggerates different corner styles according to the bike’s overall chassis dynamic, rather then specifically emphasizing edge grip or trail braking. Which is why the Honda wins, perhaps unexpectedly. With its limitations in grip, suspension performance, weight transfer and engine performance, Michael takes a wider, sweeping approach which plays to the Honda’s strengths (or minimizes its weaknesses) – hence the highest apex speed (or maximum lowest speed).

The Ducati, in contrast, is all about 205bhp point-and-squirt – Michael drives it to the peel-in point, turns, and fires it out again; maximum lean angle on a sweeping line is not the fastest way to get the Streetfighter through a corner. And, in that sense, it’s perhaps less enjoyable in this kind of corner. If you’re faced with an Alpine pass packed with hairpins, perhaps the Ducati would be more tiresome than an Africa Twin.

The Piaggio is struggling with ground clearance limiting its apex speed – it physically can’t corner any harder. And the Yamaha again wins points for being a game contender.

CONCLUSION

The winner, on paper, is the Ducati Streetfighter; Michael has more confidence in it, it manages to deploy its 205bhp in a way that allows the rider to extract a lot from it without being intimidated. The Suzuki is less impressive in the corners, and shows how far the naked streetbike class has come in terms of meeting the needs of today’s sporting rider on track – perhaps suggesting litre sportsbikes are evolving themselves out of the realm of delivering the best riding experience for handy track day riders.

But the real winner here is Yamaha’s Tracer 7. Unhindered by off-road-style wheel and tyres sizes, tall suspension and masses of horsepower, the simple parallel twin shows how effective – and how pleasurable – useable, real-world performance can be.

But the real answer to who’s king in the corners is – and this sounds like a fudge – we all are. Modern tyres, brakes, suspension, electronics and understanding of bike dynamics has given all bikes the capacity to achieve cornering performance undreamed of only a few decades ago. There are very, very few bikes can’t be ridden with a cornering confidence that would’ve had us in the hedge back in the 1990s. And for that, we should all be thankful.