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Braking on Corners


XO71
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Hello everyone.


Last night on my daily commute home by car in stop-start traffic, a situation arose in which I wondered what I would have done on a bike.

Rounding a curve on the A2 at around 60mph, the cars in front started braking, as I did too, all in good time, but I dropped to under 40mph before the road straightened. I know it's not really something you should be doing in a car either, but on a motorcycle I understand the consequences can be horrendous.


I was told when tootling around at not much above walking speed that I should use the back brake if absolutely necessary, but in a situation where heavy braking or carrying on at speed toward braking traffic are the only two options, you wouldn't want to use the back brake. Is that right? So, what would seasoned riders do in such a situation? Is it a matter of looking further ahead down the road and anticipating such situations?


Many thanks,


Mark

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You can brake in a corner, but it's a trade off, ie you can brake much less. In your general bike training it's easier/safer I think to just go with the "don't touch the brakes in a corner" mantra.


In general road riding I'd be inclined to agree with your final statement. Aim to stop in the distance you can see to be clear. And most of that heavy braking would need to be done once you'd got the bike back upright.


For everything else I guess there's swerving..... (also not ideal but better than sliding)

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Thank you, gents. I see motorcyclists going through at 100 mph or so, and worry for their safety. I'm not interested in that kind of riding, but the experience yesterday made me think.

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You can brake gently but you would need to decrease the lean angle proportionally otherwise the bike would flop down onto the road. But don't overthink it, you would probably do it automatically. Some would just stand the bike up and hit the brakes.

I remember my cousin saying years ago that he touched the brakes in a corner and the bike stood up! As if the bike did it on it's own :D

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Thank you, gents. I see motorcyclists going through at 100 mph or so, and worry for their safety. I'm not interested in that kind of riding, but the experience yesterday made me think.

 

Bikes are more stable over 100mph - much safer.

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Bikes are more stable over 100mph - much safer.

 

Absolutely, gyroscopic stability and all that. On the other hand, the bike becomes slightly less stable upon impact with the rear end of a bimbling car driver oblivious to your approach. Don't get me wrong, as someone who admires anyone who manages to keep a bike upright for more than ten seconds, I am full of respect for the guys who can ride like that. Just, I know I'm never going to try!

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Bikes are more stable over 100mph - much safer.

 

Absolutely, gyroscopic stability and all that. On the other hand, the bike becomes slightly less stable upon impact with the rear end of a bimbling car driver oblivious to your approach. Don't get me wrong, as someone who admires anyone who manages to keep a bike upright for more than ten seconds, I am full of respect for the guys who can ride like that. Just, I know I'm never going to try!

 

😉

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Your main problems with braking in a corner are the laws of physics, as you have lean angle you loose available friction due to the forces acting through your tyre, when your upright all of the grip is available for braking as you lean you take up a percentage of that which increases with the lean, depending on how hard you brake the bike is going to want to stand up and move weight goes to the front which under heavy braking will prob upset the stability.


You can brake in a corner and it can be used to help get you round a corner but your best off trying to avoid it.

Edited by Bender
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Thanks for the input, everyone. I was interested in how people cope with such situations. I suppose the answer is obvious, and the same as in any given situation; that anticipation of the road conditions ahead will allow a measured, un-panicked and timely response, minimising the likelihood of locking a wheel, which is where things go downhill.


I hope you'll forgive me, but the physics of the situation interest me (it's my job!). The reason the bike tends to stand upright as you brake on a curve is that, since the bike is in contact with the ground, only it has a force acting on it to undergo the centripetal acceleration necessary to travel around the curve. Under braking, the rider will tend to obey Newton's 1st Law of motion, and carry on in a straight line, unless they essentially pull on the bike to help them round (which they will hopefully do!). The result is an increased moment about the point of contact with the road acting to make the bike upright. In fact, this moment exists even without braking, since the bike's centre of mass is above the point of contact (again, hopefully!). This explains why you sometimes see a motorbike travelling on upright after dumping a rider, although you don't with a bicycle due to the relatively low centre of mass. This means that the bike requires some input to remain banked (subtle counter-steering?). Presumably, increasing this input would allow the bike to remain banked under braking. Not that I'm going to try. :D

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Braking harder and leaning more together is fine until you run out of grip which on a UK Road with Street tyres is likely to happen quickly, look at some YouTube video where racers on track, getting it wrong, usually involves them being catapulted high-side, as the bike looses grip then regains it or if they lucky simply sliding away from them


Look at trail braking


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Edited by Bender
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Well if I understand correctly you would not be leaning that much on such a corner (as it is not that tight), so you will still have braking available to you, not 100% braking but more than enough to stop at that type of speed. The tighter the corner, the more you would lean the less braking available to you. However, tight corners on roads are taken very slowly so you would still be able to stop in time, unless you are riding over the limits then yes you probably will fall off, so ride at the right speeds and lean angle and all should be fine. But always put the motorbike as straight as possible to increase braking available to you.


Always try to approach corners wide as well so you can see whats around it sooner, but if the corner is real tight I would not recommend going too wide because idiot driver love coming onto your lane in tighter corners so just take them slower.



https://www.youtube.com/watch?v=nthXJElRxrU[/url]

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  • 2 months later...

Is it a matter of looking further ahead down the road and anticipating such situations?

 

This. This is basically all you do for 35-40 mins on your MOD 2, and the rest of your biking life! Always assume that the people in front/behind/side roads are out to end you.


Anyway I try to shave speed off in the car and on the bike by breaking before the bend. Braking is an automatic thing tbh but i think i usually use the back break if just shaving a little off and reserve the front break for twistier upcoming bends where i need to drop a gear or so as well. You'll know the sort, the bends that have warning signs beforehand. Believe the signs.


Even on less bendy bends i also at least ease off the throttle slightly just in case something is going on up front I couldnt see! its all in the anticipation!

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Slow in.... fast out. When there are a series of bends, set yourself up as you leave one to enter the next. It should be smooth and progressive, not jerky. And as ever, always be able to stop in the distance you can see to be clear. That's it.

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Thanks for the input, everyone. I was interested in how people cope with such situations. I suppose the answer is obvious, and the same as in any given situation; that anticipation of the road conditions ahead will allow a measured, un-panicked and timely response, minimising the likelihood of locking a wheel, which is where things go downhill.


I hope you'll forgive me, but the physics of the situation interest me (it's my job!). The reason the bike tends to stand upright as you brake on a curve is that, since the bike is in contact with the ground, only it has a force acting on it to undergo the centripetal acceleration necessary to travel around the curve. Under braking, the rider will tend to obey Newton's 1st Law of motion, and carry on in a straight line, unless they essentially pull on the bike to help them round (which they will hopefully do!). The result is an increased moment about the point of contact with the road acting to make the bike upright. In fact, this moment exists even without braking, since the bike's centre of mass is above the point of contact (again, hopefully!). This explains why you sometimes see a motorbike travelling on upright after dumping a rider, although you don't with a bicycle due to the relatively low centre of mass. This means that the bike requires some input to remain banked (subtle counter-steering?). Presumably, increasing this input would allow the bike to remain banked under braking. Not that I'm going to try. :D

 

Have a look at Total Control by Lee Parks. He explains the physics of motorcycle control very well.

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I know most will probably frown upon it but I loves me abit of trail braking, but to the topic of this thread generally say you are doing 60 mph on an a road bend which wont be all that tight I'd guess that the braking needs would be within the available grip limits at the given lean angle, and it wouldnt necessarily mean that the bike would stand up.

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The bike will naturally stand up as you are transferring weight from the rear to the front wheel. You can counteract the bikes tendency to drift wide in this situation by adding more counter steer.

Go out and practice it. Get it into a bend and lightly use the front brake until you feel the bike going wide. Then add more counter steer. You’ll tighten back up.

Practice with differing pressures of front brake.

It’s a good skill to get good at

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I know most will probably frown upon it but I loves me abit of trail braking, but to the topic of this thread generally say you are doing 60 mph on an a road bend which wont be all that tight I'd guess that the braking needs would be within the available grip limits at the given lean angle, and it wouldnt necessarily mean that the bike would stand up.

 

...me too! Must be a zx6r thing. possibly as we have no engine braking :lol:

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Thanks for the input, everyone. I was interested in how people cope with such situations. I suppose the answer is obvious, and the same as in any given situation; that anticipation of the road conditions ahead will allow a measured, un-panicked and timely response, minimising the likelihood of locking a wheel, which is where things go downhill.


I hope you'll forgive me, but the physics of the situation interest me (it's my job!). The reason the bike tends to stand upright as you brake on a curve is that, since the bike is in contact with the ground, only it has a force acting on it to undergo the centripetal acceleration necessary to travel around the curve. Under braking, the rider will tend to obey Newton's 1st Law of motion, and carry on in a straight line, unless they essentially pull on the bike to help them round (which they will hopefully do!). The result is an increased moment about the point of contact with the road acting to make the bike upright. In fact, this moment exists even without braking, since the bike's centre of mass is above the point of contact (again, hopefully!). This explains why you sometimes see a motorbike travelling on upright after dumping a rider, although you don't with a bicycle due to the relatively low centre of mass. This means that the bike requires some input to remain banked (subtle counter-steering?). Presumably, increasing this input would allow the bike to remain banked under braking. Not that I'm going to try. :D

 

Spot on, as said best avoided but you can brake & apply more active steering input ( counter steering ) to keep the bike on the same curve, eventually though we run out of grip.

My take on the op question is the same as most, distance you can see to be clear etc but in an absolute emergency I'd stand the bike up on maximum brakes ( if there's road) then turn in off the brakes, which I had to do the one time going into Goddards way too fast at Donnington Park.

I do try to get all my braking done before turning though,you know, ideally

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If you'd like some more bike physics @x[mention]XO71[/mention] When I'm riding an outfit I mean a normal sidecar with a chair, when I roll off or brake the outfit starts to turn right with no input from me on the bars :lol: the limit is when the front loses grip & you go straight on or eventually gamboll to the left :shock:

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