Downhill corners are most dangerous

Wide entry, late apex safest on-road Downhill corners most dangerous

A combination of downhill slopes and corners is the most dangerous for riders, according to one of the most comprehensive motorcycle crash studies in the past 35 years.

The study by the Virginia Tech Transportation Institute for the American Motorcycle Safety Foundation used 100 riders with five video cameras on their bikes for several months and over half a million kilometres.

It produced a lot of data which is still being processed and analysed.

The Virginia Tech study is the first major crash survey since the comprehensive and often-quoted Hurt Report of 1981.

Obviously motorcycles have changed a lot since then. They are lighter and more powerful, have better tyres and handling and many have rider tech aids such as ABS, traction control, etc.

We have already looked at some of the findings of the Virginia Tech study here.

But there is one important aspect we wanted to investigate further.

We knew that corners were a danger for riders, increasing the likelihood of a crash or incident by two.

However, the report says that if it’s downhill it increases the risk by four.

Why are downhill corners risky?Wide entry, late apex safest on-road

It is most likely because riders are not using their brakes correctly.

When you brake for a corner, the weight shifts forward and compresses the forks.

This is even more pronounced if the corner is downhill as you have to brake harder to counteract gravity and there is already more weight over the front wheel.

With the springs compressed, the forks cannot deal with surface irregularities as fast or efficiently as they can when they are in their normal position.Downhill corners most dangerous

If riders hold their front brakes through a downhill corner and hit a bump or have to readjust their line, the bike cannot react or steer properly.

It’s a reminder that we should get all of our front braking out of the way before entering any corner.

Some riders still prefer to hold a bit of rear braking through a corner, but never front brakes.

And remember the word of world champion driver Stirling Moss: “It is better to go into a corner slow and come out fast, than to go in fast and come out dead.”

13 Comments

  1. Downhill corners are no more dangerous than the rider.
    If you know what you are doing, you don’t give them a second thought,
    it comes naturally how to handle the road.

  2. While I’m sure this study has found some valid reasons for reporting what it has, I think the biggest cause of accidents in downhill corners is the riders visual anxiety.

    The riders eyes/brain see and register a situation that ‘scares them’ and this causes many riders to do things that they wouldn’t typically do in a corner they were more comfortable with. Things they do are: stand the bike up (usually by applying even more brake pressure), look straight in front of them rather than through the corner and leading with their shoulder, feeling like the laws of physics are going to fling you off into the trees which gives them that uneasy feeling of the unknown and being outside their comfort-zone.

    Personally, I think that braking can actually stabilise the bike entering a downhill corner. But the braking needs to be done with some finesse and with both brakes – using only the front brake makes the bike sit up and go straight, whereas using the rear brake as well (proportionately) helps cornering stability by pulling the bike back into the corner. If the bike has a linked system, only the front brake should be used.

  3. Consider using a lower gear than normal when going downhill. This increases the revs into the area which gives more engine braking. This allows you to control the speed using a more subtle method of speed control, being throttle control.

    I have basically eliminated the need to brake downhill by using my gears and throttle more actively.

  4. You can’t brake as quickly so you have to brake early. That is the most important thing you need to know about downhill braking. If too much front brake is used on steep downhills (where there is good traction) the bike could flip over forwards. The bike won’t flip over forwards from using the rear brake so rely on it more than you would on a level road. The combination of front end dive and the angle of the hill could make you feel like you are going to fall over the front of the bike and some riders may react incorrectly. Front end dive while braking is caused partly by weight transfer and partly by the angle of the telescopic fork front suspension (mechanical dive). The rear brake contributes to weight transfer but it doesn’t cause mechanical dive. On steep downhill corners the bike may speed up when the brakes are released so you may have to use the rear brake through the corner to maintain a suitable speed.

    If there is gravel or anything slippery on the road when braking in downhill corners the wheels will slide. If the front wheel slides it will turn the bike the wrong way and you will run wide (possibly into oncoming traffic or off the road) or fall over. If the rear wheel slides it will turn the bike in the direction that you want to go but you will have to vary the brake pressure to control the slide. In these situations I sometimes use only the rear brake. If your bike has non-adjustable ABS it will back off the brakes leaving you with almost no braking at all. ABS on the rear brake is possibly the stupidest thing that has ever been fitted to a motorcycle. Every situation is different, so it is hard to give definite ‘rules’. You need to be able to adjust to the circumstances and vary your braking as necessary. But most of all; – You can’t brake as quickly so you have to brake early.

    1. Probably one of the reasons that a lot of crashes happen on downhill corners is because riders aren’t aware of how much earlier you have to brake. It creates a false illusion. You could be braking at the maximum possible for your bike on that corner but because you have to brake more gently and over a longer distance than you usually do it makes you feel like you are being overly cautious (‘chicken’). Then you may tell yourself to go harder next time, with disastrous results. And remember, ABS does not improve the braking capabilities of the bike. If you brake too late it will do nothing to help you. It simply backs off the brakes and you will overshoot the corner.

    1. It depends on the system, Robert. On early systems both controls applied both brakes. You could not use either brake on its own. That was a really stupid idea because in situations like those described here you may want to use the rear brake only, especially if there is gravel or something slippery on the road. I would avoid buying a bike like that. On modern linked systems the hand lever applies both brakes, and the foot pedal applies only the rear brake. These systems shouldn’t cause any problems. Does anybody know of a recently released current model bike where you can’t use the rear brake on its own?

      I see no reason for having linked brakes on a motorcycle. I have always considered them to be a lazy persons braking system because you can use one control instead of two. However, if you do that you don’t have full control over how much braking is applied at each end. My preference is to have completely independent control of the brakes without any electronic interference (ABS), because I am good at it.

      1. There are many reasons by linked brakes make sense and improve braking, especially in corners, but the main reason is that two wheels braking actually stabilises the bike entering, and throughout, a corner – using only the front brake makes the bike sit up and go straight, whereas using the rear as well (proportionately) helps corning stability. The linked braking systems are very good at doing this, especially the proportionment of the pressure. For those riding a long time like me, if you remember, it’s one of the reasons you gently used the rear brake in the corner – to help pull you into the corner… We were also told to always told to finish your braking before the corner – to avoid ‘straight-lining’!

        So I would suggest that you should and can use brakes in corners, just understand what you’re doing and how much pressure to apply. And yes, (before the howls can be heard), tyres do have a finite level of grip, much of which is being used during cornering, and which can be overcome with the application of the brakes as well, (but I think you’ll find it is far greater than what you might expect).

        What I’m saying is ‘be balanced’ in the use of the brake when cornering; loading the front wheel actually gives more grip as there is more force on the tyre (just like what happens in an emergency braking manoeuvre) and this will provide more adhesion in the corner.
        Unfortunately, it also means the suspension is compressed and so uneven surfaces (bumps or dips) can upset the bike a little more easily, but typically this isn’t the cause of accidents because the loading of the suspension is part of the force being applied to the bike in a corner anyway…

        The biggest cause of accidents in corners is the riders visual anxiety. The eyes/brain see and register a situation that ‘scares’ them and this causes many riders to do things that they wouldn’t do typically in a corner they were more comfortable with. Things they do are: stand the bike up (usually by applying even more brake pressure), look straight in front of them rather than through the corner and leading with their shoulder, feeling like the laws of physics are going to fling you off into the trees.

  5. Arh ha, and that multiplies in the wet, and for those of us who tow a trailer on long haul adventures, it can be down right nerve racking.

    Speaking of which, catch ya all in 3 weeks, off to the apple isle, bike and trailer. Riding, fishing eatin and tasting the good drops, sleep then repeat.
    Have a Merry Christmas and a safe yet rockin New year, to all.

    Ride free and safe.
    GOB

  6. I suspect mainly a combination of (a) a fear of downhill; I see many who are not comfortable with significant downhill in general, and the downhill “offs” I’ve witnessed have all contained an element of panic, and (b) misjudged braking, as you say…

    1. 100% agree. The number of riders who look like they crapped themselves as they come into a downhill corner is so high. Usually they crash because visually they had scared themselves and totally threw away their normal cornering approach and panic instead. Riders don’t trust the bike, themselves or the road. This comes with experience, advanced and honed skills and always following tried and true cornering methods.

  7. Push forefoot on footpegs, lift butt a tad pushing your weight further back in downhills. Head centre behind bars, not over the front. Relax. Breathe. Loosen grip. Look for next corner or section. That should help for starters.

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