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Cornering perfection

Science behind cornering
Marc Abbott
22 Jul 2015

Getting it right will make you faster and safer, so it's time to take a look at the skills and science of cornering.

It makes little difference what type  of rider you are – the skills required to quickly dispatch corners, either   alone or in a group, are universal. And essential. Colin Batchelor of Total Cycle Coach explains it in a nutshell: ‘In a sportive you’ll be with riders you don’t know and often on unfamiliar roads. Poor cornering technique brings the risk of obstructing others, crashing, losing control or slowing down unnecessarily, not to mention wasting energy. In a race, it’s a vital skill that will not only keep you and your fellow racers safe, but also keep you in contention.’

Even when riding on your own, skilful cornering will increase your enjoyment and boost your performance. With an understanding of how to make the most of your momentum, and a grasp of the underlying scientific forces involved, you’ll give yourself the best chance of staying upright and getting to the final hill with the energy reserves you need for that decisive attack or one last dig to beat your personal record. 

The perfect approach

Have you ever found yourself barrelling into a turn and wondering if you’ll make it safely out the other side? Ex-WorldTour rider Dan Lloyd explains the essentials of setting yourself up for the perfect turn: ‘Try to judge how sharp it is. If you can’t see where the road goes, look at the treeline, and avoid drain covers at all costs, even in the dry.’

‘You also need to look at the conditions,’ Batchelor adds. ‘Is there loose gravel? Has the corner been patched up? Is it wet? Your plan should be to go in wide while riding on the drops, clip the apex and exit wide. And if you can’t see the exit, you’ll need to scrub off more speed coming into the turn.’

Road bike descending skills

The message is that the approach to the corner is the critical part of the process, determining whether you glide round with speed and grace or make a potentially expensive hash of it. Once you’ve assessed the road surface and have a decent idea of where your exit is, the crucial skill in entering the corner is the safe and efficient use of the brakes. ‘Brake before you get to a corner, not when you are in it, unless it’s totally unavoidable,’ advises Batchelor.

‘I tend to move into the middle of the road for left-handers,’ adds Lloyd. ‘Once I’ve checked there’s nothing coming up behind, I’ll take up that position and make sure all the braking’s done before entering the corner. That’s especially important when it’s wet. The wheels will wash out from underneath you if you grab the brakes when you’re already committed and leant over.’

Slowing yourself down in good time for the corner relies upon an understanding of what your tyres are doing, and how your braking input affects the physics of your bike, especially if you’re hurtling down Alpe d’Huez. Professor Tim Gordon, head of engineering at the University of Lincoln, is an expert in vehicle dynamics. ‘When braking in a straight line for the corner, we feel a tipping forward,’ he says. ‘This has the net effect of loading the front tyre more than the rear. This load transfer compresses the front tyre, increasing the contact patch, meaning it has more grip and can sustain more braking force. That’s why you bias the braking towards the front to slow down more quickly. Taken to the limit, the rear wheel can lift, so it’s important to move your body weight rearwards to compensate.’

How you select where to turn in depends greatly on whether you’re in a closed-road event or not – the difference being the need to stay on the correct side of the road.

Batchelor offers this advice: ‘For a sharp corner, you need to enter as wide as is safe and aim to clip the apex, before exiting as wide as possible. And try to anticipate the gear you’ll need on the exit. If you come into it in 53/13, that’s a pretty big gear to start pushing after you’ve slowed for the turn. Also, riding on the drops lowers your centre of gravity, which improves grip and handling.’

All you need to do now is take the corner without falling off. The first thing to remember is to keep your outside pedal down, which will help with stability and prevent your inside pedal from digging into the road and upending you as you lean over. Then you’re at the mercy of your tyres and the road conditions, and this is where the science kicks in. 

Turning technical

‘In a “steady-state” turn, you have the force of gravity on bike and rider, plus a frictional force from both tyres generated where they meet the road,’ says Gordon. ‘What we’re concerned with here is called centripetal acceleration. If you corner to the left, you have to generate an acceleration to the left, which in turn generates a curving motion.’

The grip provided by the tyres when the bike leans over creates centripetal force – a lateral force towards the inside of the turn that’s balanced out by an inertial force (sometimes referred to as a ‘centrifugal force’) to the outside of the turn.

How to corner a road bike

‘The angle of lean is related to the turning radius, so making corrections mid-corner, relies on the skill of the rider,’ Gordon says. ‘Generally speaking, a low mass centre is more stable, but doesn’t affect the angle of lean, but if you’re taller it does have the effect of making the lean angle feel more pronounced.’

But is there a way of maximising the grip of your tyres by reducing your lean angle and still being quick through the bend? ‘The more you lean your bodyweight into the corner, the less the bike leans, and the less force is generated,’ says Gordon. ‘For a given curve, the force is dependent on the speed and the radius, but by leaning your body into the turn more, you can have less angle at the tyres, and by controlling this relationship you gain an extra degree of control.’

As well as adjusting your lean angle, you also need to read the road conditions, as cornering in the rain will obviously offer less grip. ‘I got nervous on wet roads,’ says Lloyd. ‘The problem with road cycling, as opposed to mountain biking or cyclocross, is that as soon as you get a bit of wheel drift, nine times out of 10 you’re going to end up on the floor. It makes it more difficult to know where the limits are, because if you find them you’re going to lose a lot of skin.’

The size of your tyres will have a big effect on the grip you have when rounding a corner, as Gordon explains: ‘Because tyres have a rounded profile that allows lean, most of the tyre forces are generated by what’s called “camber thrust”, the deformation of the tyre. Tyres with a 25mm diameter can potentially corner more quickly than 23mm tyres because there’s a bigger contact area. This depends on things like heat and road surface, but the larger the area of tyre in contact with the road, the higher the force that can be sustained before the tyre loses grip.’

‘There’s a sliding point with every tyre,’ says Steve Lampier of Team Raleigh-GAC. ‘And road conditions play a big part – you have to learn to read both. Newly laid asphalt will still have oil creeping up out of it, for example. If there’s gravel or potholes, you need to adjust your line before you go into the corner – and above all, don’t panic.’ Tensing up as you go into a corner will tend to make you grip the bars tighter, which will only make the bike more difficult to handle. 

Group think

When riding in a group you’ll need to make allowances and be prepared to adjust your approach to cornering. ‘For any given corner there will be an ideal line, but it might have another rider on it,’ says Batchelor. So you may have to change your planned line at the last minute, and there are ways of making this easier. ‘On a descent you’ll find the riders string out,’ says Lampier. ‘If you’re following the wheel in front of you and someone dives down the inside and pushes you wide, you’ll be better able to respond if you’re on the drops. But if the guy in front of you wants to go at a million miles per hour and you’re not comfortable with that, let him go. You should always tackle downhill corners within your own limit.’

Road bike cornering skills

Riding in close groups may also throw up a situation where you feel you need to brake mid-corner. ‘There are a few things you can do to manage your speed,’ says Batchelor. ‘Apply the brakes smoothly and gently, and keep the braking even across the front and rear. If you snatch either brake, that wheel is liable to slide out from under you. Push down on your outside leg as usual to aid traction. In extreme cases lean the bike more than you lean your body, so your backside is lifted from the saddle or moved to one side. This puts more weight over the wheels, giving you more grip. Importantly, breathe out and relax. This will help you retain control and, if you do come off, it could reduce the likelihood of injury.’

Get your cornering spot on and your speed, safety and riding enjoyment will improve dramatically. Plus, if you’re riding competitively, your chances of getting in a race-winning break or sprinting out of the final corner are vastly improved. Batchelor describes the scenario: ‘In a race, riders will often attack coming out of the corner, and if you’re losing position due to poor cornering you’re immediately under stress and using vital energy sprinting to regain contact. Practising your cornering technique is just as vital as practising sprinting or climbing.

Lampier is an old hand at crit races such as the Tour Series, where arguably the value of cornering prowess is at its highest. ‘The problem in UK crit racing is the whole “dive-bombing” situation. People dive down the inside or turn in very quickly in front of someone else. It’s a scary thing to do because you’re 100% committed, but it often works and you can learn to do it with experience. In a crit, you might go round the same corner 50-odd times, so confidence comes with familiarity.’ Dive-bomb someone on a descent in your next foreign sportive, though, and you might find yourself in a world of trouble – or at least on the receiving end of some serious verbal abuse. That said, the careful overtake into a corner is eminently possible providing you read the severity of the bend and time it right.

As for how you garner these cornering skills, Batchelor suggests, ‘Find a quiet stretch of local road and practise riding corners: sharp corners, shallow corners, left-handers and – if it’s safe and you have a clear view – right-handers, at a variety of angles and speeds.’

Finally, it seems that if you come from a certain sporting background, you might already have the edge. ‘We’ve a lad in our team, Brad Morgan, who comes from downhill skiing,’ says Lampier. ‘When we’re going round corners at 60kmh, he’s seeing things at a different speed because he’s used to doing it at 100kmh, so he’s really smooth. It’s the same with people from motorcycling – they see things differently to someone who’s come from the golf course.’

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