There She Blows!

Riding a motorcycle has many challenges, some of which are thrilling and some of which are practical and some of which are just a little on the scary side.

Riding in general will expose the rider to airflow as the motorcycle moves forward and even on a calm day, the faster the ride, the more airflow the rider will be subjected to. This all makes sense to riders and there are various ways to minimise the effect of ‘wind’ or airflow on the rider by either using wind deflectors, windshields, laying prone and tucking in, or wearing motorcycle clothing that is relatively snug around the body and wearing a full face helmet.

The affect of all these aids is to either deflect the airflow around the motorcycle and around and above the rider or reduce the amount of resistance the rider produces when interacting with the airflow. This is essentially the basis of aerodynamics: make something that is designed, shaped & streamlined as possible so that it ultimately offers up the least resistance to wind. When air flows around a rider and motorcycle, the head on air ‘splits’ with some going either side and some beneath and over the top.

This airflow should move in a straight line but as it meets the rider and machine, it is diverted over the surfaces. As it does so, there are surface layers of air called boundary layers which depending on how clean, smooth & uniform the surface is, will generate different amounts of swirling air which is turbulence which not only causes drag at the surface but then is further creating turbulence as the airflows meet at the rear of the rider and machine. Ultimately the airflow around the rider should flow over as smoothly as possible and meet at the rear and continue in a smooth path. If that airflow is disturbed, it will create turbulence which will further create drag which add to the slowing down and discomfort.

A wind deflector or windshield make the airflow rise higher over the rider, although it is deflected more, it still retains its smooth qualities, therefore less drag.

A full face helmet acts as a smooth wind deflector, whereas an open face will add more resistance.

Loose clothing will offer a more undulating surface which will cause the airflow to alter rapidly, which causes more turbulence.

Being tucked in actually minimises the surface area of the rider to the air, therefore the air will flow over the rider and retain more of the smooth quality. As the total surface area of rider and machine is minimised, then the resistance to the airflow is minimised, therefore the turbulence is less and so drag is less.

This is the basis on which so much emphasis is placed on aerodynamics in racing cars and on racing bikes. If you can make a motorcycle and rider move through the air with the minimum amount of air resistance under varying profiles, then there will be less drag which will want to slow the bike and rider down. If there is less drag then there is less engine power required to overcome that drag, therefore there is more power available which means the rider can go faster.

This is all very well on a racetrack but what does this mean to a road rider and what happens when the wind in not calm.

Well, the same principles of airflow fluidity and that what would opposed that or restrict that fluidity apply. The problem is that wind is rarely uniform in direction and in speed, certainly this is the case at the road surface. Therefore the airflow that a rider meets can suddenly change direction, speed and density.

If riding on a windy day on an exposed road without any obstructions on either side, be them buildings, trees, hills, hedges or any large vehicles on the road, then the wind under normal circumstances will generally come from one direction at a relatively constant speed. (In this situation I am talking about a given wind on a given day. The reality is that wind can have lots of properties and which is influenced by other variables which will cause it to change.)

If the wind is coming from head on, then the rider will generally feel that as a stronger wind and may have some discomfort whilst being buffeted. The rider may ease this somewhat by tucking in and although there will be a greater demand from the engine, it will not be so noticeable for the road rider’s requirements.

If the wind is coming at an angle or from the side, then the steering may seem ‘loose’ and the motorcycle may drift away from its intended path, with the wind. I.e. the wind will blow the bike off course. The rider may slightly steer or lean into the wind to counteract this.

The key thing to remember here is that the rider should be ready for the wind, stay relaxed and be comfortable. Try not to over control or be too stiff in the upper body. Try to tuck in somewhat, stay relaxed on the controls, accept some minor movements and deviations and then make the corrections in a positive and smooth manner and if need be slow down in gradual phases which will help to stabilise the ride.

Anytime when the ‘riding package’ is changed from a solo rider and bare machine to either carrying baggage or pillions, the airflow around the motorcycle will change and the surface area will change, hence there is more likelihood of turbulence around the bike and more chance of the wind causing the rider and machine to be blown off course. Ride at a slower appropriate speed and at a speed that feels comfortable and always give yourself that extra margin of error. Be sure that suspension settings have been properly adjusted for the change in weight and be prepared that the steering will be lighter on the front due to the added rear weight.

Much more likely is if riding on a road that has obstructions on either side or large vehicles on the road, then the rider will be riding into fluctuating wind properties. It will be smooth, then blustery, gusty then calm, etc. Just as the air will have to flow around a rider and machine, it will also be forced to flow around obstructions, which will create large amounts of turbulence. In general, the larger the obstruction and the less rounded it is, the greater the turbulence will be.

As the air flows around an obstruction the airflow tries to meet behind on the ‘leeward side’ which is some way behind the rear surface of that obstruction. The space in between is a void of ‘calmer air’ which if you are a racer is the place you would like to be (Drafting) because you are able to travel at the same speed but for much less power.

Where the air meets is the start of a long trailing area of high turbulence, which when ridden through can be uncomfortable and can cause the rider to be blown off course. Hence if riding along with a strong crosswind and there is a large building in between the rider and where the wind is coming from, the rider can ride from a ‘smooth’ area to a ‘very rough‘ area which can be quite disconcerting, especially if the rider is not prepared for it. Riding through this area or even if riding through the void can actually cause the rider to be ‘sucked‘ off course.

Again the key here is to be prepared for it, note where the wind is coming from and estimate how strong it is. This can be done by looking at the surroundings for pointers: trees, leaves, flags, windsocks, blowing debris etc. Give yourself extra space to allow for minor deviations and if necessary reduce speed which will stabilise the ride.

Any obstruction to the wind will create varying degrees of turbulence and one of the most hazardous situations is when either overtaking a large vehicle or being overtaken by one. The large vehicle either is the obstruction to a strong wind which creates turbulence or by its speed is generating turbulence around the vehicle. 

The rider can encounter the ‘blow’ or ‘suck’ and should be prepared for the rough ride, reduce speed if appropriate, allow extra space and steer away, do not over control and stay relaxed…which be may easier said than done.

Another key point to consider in high winds is not only how the motorcycle will be effected but also how other vehicles will be effected. Many drivers will not be used to driving in high winds and may also be blown off course and high sided vehicles are particularly susceptible to the wind effects. The rider should always monitor their own riding but also make extra space for other vehicles and make allowances that other drivers may be struggling with the conditions also.

Probably the final thing to consider is how the strong wind will create flying debris or surface debris on the roads. Especially when riding on roads with nearby trees, the rider should pay particular attention to falling debris and any on the road which may destabilise the ride.

Every rider should factor in the weather and the wind and how that may potentially effect the ride. Consider the route and potential areas of turbulence, also how other vehicles may be effected. In some cases it might mean that a rider may choose not to ride, especially if they are not confident…and this is, by no means anything to be ashamed about.

Allow extra space between vehicles, especially large ones, stay relaxed, do not over control and reduce speed if necessary, bearing in mind that most motorcycle accidents in these conditions are more to do with over control or not allowing or factoring for space or debris. 

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