Emergency braking: Clutch or de-clutch?

[Metastable]

I'm with P.dath on this one.

Your limiting factor when you are emergency braking is how hard you can hit the brakes. The engine isn't going to provide any significant deceleration in an emergency. It becomes second nature if you practice enough to grab the clutch and the brake at the same time..... while you are grabbing them you stab the rear and as you quickly load the front you start to reduce pressure on the rear if you are on a sportbike.... a cruiser is different, you'd stay on the rear with more pressure.

This all has to be second nature and you can't be thinking through it. You need to practice A LOT and you need to practice from whatever the fastest speed you ride at.... otherwise you won't know what your bike will do until it is too late.

Another advantage like P.dath said, if you have the clutch pulled in, then you won't accelerate accidentally. Also, be careful with parking lots, they can be dusty and the front will lock much easier... just be ready to let go of the front brake, so that you don't tuck it.

[CookMySock]

Locking up the front affects bike stability.

Locking the rear affects stability too. If you do manage to lift the rear wheel, ANY braking during that time whatsoever with the clutch in will completely stop the rear wheel turning, with the resultant mini-slide to restart it once it touches down assymetrically. If you are really unlucky this mini-slide will turn into a maxi-slide and then you are on your arse.

Dealing with an obstacle on the open road at 120k mid-corner is completely different to experimenting in a carpark, and in the end its the former that kills motorcyclists. There is also the situation that most of the time the disaster is averted by the time you have scrubbed 50k off your speed, so coming to a complete halt is not relevant.

in the wet, actively shut the throttle and apply both brakes firmly and evenly, releasing somewhat either to steer if you judge that to be safer than braking in a straight line, or if you detect any step-out, wriggle, or otherwise.

In the dry, actively shut the throttle and engage brain fully if it wasn't already, and belt both brakes really fucking hard and then modulate them to deal with any unfolding dramas as they arise. The bike will buck and dance around, but it will pull up a lot quicker than you think. You don't have time to piss around the the clutch, and your left hand fingers are better off wrapped firmly on the bars carving some expertly laid-out curve that gets you around the situation, because plain as day you are unlikely to be completely stopped before you reach it.

If you are going to practice this, and you should, get on the track and do it please, or else you might end up under a truck going in the opposite direction.

[Crasherfromwayback]

First the brake. HARD

First the brake gently and squeeze it progressively and smoothly harder to avoid locking the front wheel.

[bogan]

People are of all different heights, with different arm lengths, and different size hands. A lot of bikes simply can't be adjusted to achieve this. And even then, I'm not sure that is a good idea, as it makes learning to blip and brake while changing down difficult. You really (for a road bike) should be able to operate both the throttle and the front brake at the same time, as opposed to either or. But that is my personal opinion, and others will think differently.

In my opinion one of the first things any new bike owner should do is adjust the levers to suit their riding position. If they ain't set up right, you can get fatigue much quicker, loss of brake feel and less control under braking, etc. If it still ain't right look at getting some different bars/clip-ons (I tried grinding the stops off my clip-ons for more adjustment, then eventually went to dirtbike style bars on my current bike). I mean, you wouldn't ride with a helmet the wrong size, your bike should fit just as good.
You can still blip, and operate them both at the same time (not that I can see why you would need to), just not under heavy braking, at which point you can just slip the clutch for a bit on downshifts if needed.

[CookMySock]

First the brake gently and squeeze it progressively and smoothly harder to avoid locking the front wheel.

And I guess there is the matter of compressing the front forks in a sane manner.

[Crasherfromwayback]

And I guess there is the matter of compressing the front forks in a sane manner.

Well if you brake like that, that'll happen. Goes hand in hand.

[p.dath]

Locking the rear affects stability too. If you do manage to lift the rear wheel, ANY braking during that time whatsoever with the clutch in will completely stop the rear wheel turning, with the resultant mini-slide to restart it once it touches down assymetrically.

The thing is, if your emergency braking to a complete halt the rear wheel shouldn't be having weight come back on it till the bike is at a near standstill.

Dealing with an obstacle on the open road at 120k mid-corner is completely different to experimenting in a carpark, and in the end its the former that kills motorcyclists.

You can't emergency brake hard mid corner in the situation you describe. The bike needs to be upright and the rider balanced before commencing emergency braking. If you are mid corner and commence an emergency brake the bike will stand up and there is a good chance you'll go wide on the corner and go off the road.

Obstacle avoidance going around a corner is a different issue. I would not advocate anyone pull in the clutch and engage both brakes in that scenario.

There is also the situation that most of the time the disaster is averted by the time you have scrubbed 50k off your speed, so coming to a complete halt is not relevant.

I guess we'll have to agree to disagree. I believe there is both a need for emergency braking to a complete halt, and "brake and escape".

In the dry, actively shut the throttle and engage brain fully if it wasn't already, and belt both brakes really fucking hard and then modulate them to deal with any unfolding dramas as they arise. The bike will buck and dance around, but it will pull up a lot quicker than you think. You don't have time to piss around the the clutch, and your left hand fingers are better off wrapped firmly on the bars carving some expertly laid-out curve that gets you around the situation, because plain as day you are unlikely to be completely stopped before you reach it.

We'll have to agree to disagree. Humans have a limited cognitive resource, and in an emergency it is usually used on the danger, not a thought out response. That's why emergency braking needs to be an automatic response - you have little cognitive ability to process what to do at the time.
Learning to engage the clutch immediately, being a single action, sounds a hell of a lot easier than learning to modulate your front and rear brake based on the feedback from the bike.

I'm also of the opinion, and I know it is not easy to achieve in an emergency, that you should not have a death grip on the bars. So I would not agree that you should have your left hand "tightly" wrapped around the bars. Have a tight grip however does cause the bike to "dance" around as you say, as it turns your body into a pivot around the bars, as the energy transfers via your arms, rather than in a straight line through the bike.

If you are going to practice this, and you should, get on the track and do it please, or else you might end up under a truck going in the opposite direction.

Although I do advocate practice on a track, I personally believe the kind of braking you do on a track is completely different to emergency braking on a road.
Typically on a track you brake from much higher speed, so the time for weight to transfer from the rear to the front is much less. Also on a track you typically do not want to bring a bike to a halt - what you are trying to do is to reduce your speed for entering a set of corners (not for a straight line) and to set yourself up for the next set of corners. Also on a track you typically want to be able to drive out of a corner - once again, completely different to the situation on a road where you are braking to save your life.

First the brake gently and squeeze it progressively and smoothly harder to avoid locking the front wheel.

+1. This is my preferred approach as well.

[cheesemethod]

You should not be concerned about locking up the rear under emergency braking. If you are braking hard the rear often locks up, because the weight comes of the rear tyre. As the rear tyre has less and less traction with the ground it becomes easier and easier to lock up. At this point the rear brake has pretty much no input. Hence it makes no difference weather it locks up.

You're making the assumption that all emergency braking is done upright on a flat piece of perfect asphalt in the dry. A while back on my 400 suzuki I was heading toward a roundabout a touch too quick, then realised I had to stop for traffic coming from my right. It wasn't raining but had done so quite heavily about 15 minutes before. The rear locked up and slid to the left with the camber of the road. I ended up stopped just before the give way lines facing 45 degrees to the right of straight, barely managing to hold the bike up. I was very lucky that I didn't end up on the ground. So I have to disagree with you there, it makes a big difference if you lock the rear up, especially in less than ideal circumstances.

Likewise pulling the clutch in should not have an impact on bike stability while emergency braking. Pulling the clutch in removes power from the rear wheel. The rear wheel has little weight on it, and little traction, and hence little drive. And ideally, you want the rear wheel to have no drive - otherwise it is fighting the brake.

The fight between the engine and the rear brake is one that the rear brake will always win (unless you are still on the throttle). I prefer to still have the driveline engaged as it gives me a buffer which prevents the rear wheel locking up.

[george formby]

Locking the rear affects stability too. If you do manage to lift the rear wheel, ANY braking during that time whatsoever with the clutch in will completely stop the rear wheel turning, with the resultant mini-slide to restart it once it touches down assymetrically. If you are really unlucky this mini-slide will turn into a maxi-slide and then you are on your arse.

Dealing with an obstacle on the open road at 120k mid-corner is completely different to experimenting in a carpark, and in the end its the former that kills motorcyclists. There is also the situation that most of the time the disaster is averted by the time you have scrubbed 50k off your speed, so coming to a complete halt is not relevant.

in the wet, actively shut the throttle and apply both brakes firmly and evenly, releasing somewhat either to steer if you judge that to be safer than braking in a straight line, or if you detect any step-out, wriggle, or otherwise.

In the dry, actively shut the throttle and engage brain fully if it wasn't already, and belt both brakes really fucking hard and then modulate them to deal with any unfolding dramas as they arise. The bike will buck and dance around, but it will pull up a lot quicker than you think. You don't have time to piss around the the clutch, and your left hand fingers are better off wrapped firmly on the bars carving some expertly laid-out curve that gets you around the situation, because plain as day you are unlikely to be completely stopped before you reach it.

If you are going to practice this, and you should, get on the track and do it please, or else you might end up under a truck going in the opposite direction.

Glad you mentioned another scenario. I don't think I have ever had to bring the bike to an emergency stop on a dry, straight, well surfaced bit of road. Certainly had to scrub off speed & change my line quickly but that is relatively simple.

Emergency braking mid corner, in the wet, on a dodgy road surface or in limited space requires a huge amount of thought, instantly. To have a hope you need to know how the environment will affect the bike before the emergency presents itself, you have to be riding "aware".

In this case I do what I have too, front brake, rear brake, clutch or de-clutch, slide the back end to straighten the bike up etc, whatever it takes to keep the skin on. But it all starts from knowing whats under your wheels & around you before you react.

The best technique is the one that works at the time. IMHO

[p.dath]

You're making the assumption that all emergency braking is done upright on a flat piece of perfect asphalt in the dry. A while back on my 400 suzuki I was heading toward a roundabout a touch too quick, then realised I had to stop for traffic coming from my right. It wasn't raining but had done so quite heavily about 15 minutes before. The rear locked up and slid to the left with the camber of the road. I ended up stopped just before the give way lines facing 45 degrees to the right of straight, barely managing to hold the bike up. I was very lucky that I didn't end up on the ground. So I have to disagree with you there, it makes a big difference if you lock the rear up, especially in less than ideal circumstances.

I did say you need to have the bike vertical and be centred on the bike beforehand ...

The fight between the engine and the rear brake is one that the rear brake will always win (unless you are still on the throttle). I prefer to still have the driveline engaged as it gives me a buffer which prevents the rear wheel locking up.

The problem is the fight results in the braking distance being increased - not what you want in an emergency stop.

[oneofsix]

I did say you need to have the bike vertical and be centred on the bike beforehand ...

Interesting take because the bit that took my attention from cheesemethod's post was the chamber. Even if the bike is upright the chamber could slide the rear wheel out. Its when the rear tries to pass the front that scares me.

[cheshirecat]

No matter what method is taken to brake bear in mind the human brain requires a thousand repetitions of the same action before it becomes a subroutine, ie happens on reflex without having to think about it.

So if practicing allow time to perfect, don't expect a few attempts in a car park or race track to do the job. What the brain does in an emergency is not always what you want.

[cheesemethod]

I did say you need to have the bike vertical and be centred on the bike beforehand ...

And that's how I started. I'm saying the camber of the road is what I think caused the bike to slide out to one side. Now while I have control over whether my rear brake is locked or not, I sure don't have control of the shape of the road under me. Perfect world techniques are rubbish, especially in New Zealand, because we are so rarely on perfect roads in perfect conditions.

The problem is the fight results in the braking distance being increased - not what you want in an emergency stop.

If the rear wheel were to lock regardless of clutch in or out, how would that make any difference to the stopping distance? (Note this is using your argument, not mine, I still don't think the rear should be locked at all)

[bogan]

The problem is the fight results in the braking distance being increased - not what you want in an emergency stop.

have you read the article in the OP? There was half a meter difference over 40m, I don't think the testing done is enough to say that pulling in the clutch is better in the best case scenario, and no evidence to say it is better in others.

[george formby]

have you read the article in the OP? There was half a meter difference over 40m, I don't think the testing done is enough to say that pulling in the clutch is better in the best case scenario, and no evidence to say it is better in others.

Yeah, I think squeezing both levers probably results in a fractionally quicker reaction & possibly a slightly more confident brake squeeze but I do not think their is a physical effect on the bike, not enough info to imply that anyway.