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 Motorcycle Safety
 General Discussion
 Panic use of the brakes
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James R. Davis
Male Administrator
17333 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 12/23/2017 :  9:51 AM Follow poster on Twitter  Join poster on Facebook as Friend                        Like
I know, you all know that panic use of the brakes is a no-no and that the front brake is more effective than is the rear brake, but do you REALLY understand these life savings concepts?

By 'panic' use I mean excessive aggressive application - 'stomping on the rear brake pedal' and 'grabbing a handful' of the front brake lever'. Either, of course, can lock the brake, stop that wheel from rotating, and result in a skid. But aggressive use of the front brake will save your life, so the trick is knowing and using that lever with enough aggressiveness to just barely avoiding a skid. In the case of the rear brake pedal - it is NEVER, EVER, NOT ONCE IN YOUR LIFE appropriate for you be aggressive with that pedal.

Anybody who has ridden a motorcycle for a while knows that the front brake provides FAR MORE stopping power than does the rear. How much more?

If you do the absolute best job possible with your rear brake (ONLY) and don't skid that tire, the best possible deceleration rate you can achieve is about 0.4g's. If you do skid that rear tire the best possible deceleration happens to be almost the same (about 0.4g's) - until your rear end washes out to the side and you crash.

If you do the absolute best job possible with your front brake (ONLY) and don't skid that tire, the best possible deceleration rate is close to 1.2g's (if the road surface and tire rubber are good AND you don't end-over). If the front tire skids you have less than 1/2 second before you are eating asphalt.

Obviously learning and practicing front brake control is worth your effort.

This little factoid just might open your eyes: When you aggressively use your rear brake the rear shock tries to lift the rear tire off the ground!!! We can talk about that if you want to.

Alan_Hepburn
Male Standard Member
200 Posts


San Jose, Ca
USA

Honda

1994 GL1500SE

Posted - 12/23/2017 :  12:44 PM
Does this get modified at all when the bike has linked brakes? I use the front brake for most of my stopping, but do use the back brake as well - the pedal also applies pressure to the left front caliper so it does provide SOME front braking. Of course, with the sidecar there is less of a chance of low siding if the rear locks up!
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James R. Davis
Male Administrator
17333 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 12/23/2017 :  12:54 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Aggressive braking tries to lift the rear wheel off the ground whether linked or not. One thinks of shock absorbers as devices designed to keep the wheels on the ground, but with weight transfer occurring the shock cannot unwind fas enough so the wheel follows the rear of the bike in an upward direction. The result: chirping of the rear tire on the ground.

Almost always a good idea to use both brakes no matter the configuration of the linking system. The rear, not for stopping power so much as anti-slew to keep the rear wheel in alignment with the direction of travel.
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onthebeach
Male Standard Member
118 Posts


Arch Cape, Oregon
USA

BMW

R 1200 RT

Posted - 12/23/2017 :  12:59 PM
I would like to know if this statement would be modified for bikes that have ABS.

In an ideal world I would be such an experienced and practiced rider that I could apply brakes as good as, or better than,
ABS. I understand that this is difficult to do on dry pavement and even more so on wet pavement.

Right now in cold and wet Oregon my bike will spend a lot of time in the garage. When that great spring day shows up I should be out practicing. I certainly will do some, but I'm likely to also go out and enjoy being on the bike again. If I end up out for a ride and some car runs a red light and I need to stop as quickly as possible is maximum use of the front brake lever and having the ABS kick in the best strategy? This is a 2016 BMW R1200RT with linked brakes and ABS.

Your opinion on trying to make use of ABS technology to achieve the minimum stopping distance?
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James R. Davis
Male Administrator
17333 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 12/23/2017 :  1:11 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Believe me, you can skid the front tire with ABS by grabbing a handful!

The same for the rear tire.

ABS is wonderful for QUICKLY compensating for over-usage, but it isn't instantaneous. The proper name for ABS is 'mistake compensating device'.

Fastest possible stopping with or without ABS is FAST (but not panic) 'aggressive' (note my early admonition) use of both brakes, then moderating (not modulating) the rear. With ABS, however, as you approach the 'slip threshold' it activates while without you can go just a little farther and, thus, stop more quickly.

If you've ever seen the roadway following the application of an ABS system you've seen skid marks! They are just not dark and obvious. Accident Investigators call them 'incipient' skid marks. They are so faint that the wind will often blow them away in short order.
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Alan_Hepburn
Male Standard Member
200 Posts


San Jose, Ca
USA

Honda

1994 GL1500SE

Posted - 12/24/2017 :  3:05 PM
It would be interesting to see the difference that a sidecar makes in how much the rear wheel lifts. With a rigid connection to the bike's frame, and the sidecar's wheel being much closer to the rear of the bike than the front it seems to me that it might tend to hold the rear of the bike down a bit, especially when there's around 200 lbs of weight in the sidecar, on top of the sidecar weight itself. I do know that hard braking tends to slew the rig to the left due to the sidecar, although it's not as dramatic on the GL1500 as it was on the Ural!

My riding style has me using the front brake a lot more heavily than the rear brake to come to a stop, but I do use both pretty much all the time.
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rkfire
Advanced Member
1715 Posts


Stratford, CT
USA

Suzuki

Bandit

Posted - 02/01/2018 :  9:47 AM   Join poster on Facebook as Friend  
I practice using my brakes to the fullest that I can. I think it's the one skill that the average rider can master with a little effort.

Over the years I keep adding to those skills with other methods that I think are helpful in emergency braking.

I cover my brake and clutch lever always. It shaves a fraction off reaction time, and I don't believe I can otherwise predict say...a deer or animal encroaching. Traffic situations where I DO worry about the other motorists, I simply slow down 5-10 mph, which then shortens my stopping distance more than skill.

I llearned pulling the clutch lever shortens stopping distance, so cover that lever too, even though originally I covered it for comfort reasons. The symetry of my hands.

My bike has a shorter wheelbase (56 inch or so) and relatively tall. Trying to make it less wheelie prone, I lowered the bars, footpegs, and seat to lower my CG. That helps quite a bit to make it less stoppie prone as well.

Can't find it now, but I was in a discussion on here about getting to threshold braking quickly. There was somewhere a mention of taking 3/4 of a second sqeeze time to get to maximum braking, and I thought that was loosing precious stopping distance.

My next bike will likely have ABS, and when that happens, I'll practice with that bike as well. My hunch is, I will be practicing getting to threshold braking without kicking in the ABS system.

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James R. Davis
Male Administrator
17333 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 02/14/2018 :  11:36 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Sorry for the delay in response. Been under-the-weather for a few weeks and the e-mail server was dysfunctional as well - in other words, I didn't get notice of your post. Sorry.

In the thread on Threshold Braking (https://www.msgroup.org/forums/mtt/...PIC_ID=13990) I tried to make sure that riders understood that any braking effort that results is a deceleration rate greater than what it would be if your tires were skidding DEMONSTRATES that you are using threshold braking.

I also said that a worthwhile skill to develop is getting to maximum braking pressure (particularly of the front brake) as quickly as possible, but not so fast that you lock the brake as a result. Nowhere did I suggest that 3/4 of a second was a good time - it is NOT. The skill you want to develop is getting to maximum braking pressure in 0.4 seconds. A speed of 0.3 seconds will almost certainly lock your brake as weight transfer takes that long to reach the front contact patch (compressing your shocks).

I like your attitude and clear thinking.
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rkfire
Advanced Member
1715 Posts


Stratford, CT
USA

Suzuki

Bandit

Posted - 02/15/2018 :  10:48 AM   Join poster on Facebook as Friend  
Just to be clear, I wasn't implying at all the 3/4 second remark came from you James.

I just have the notion that braking is the one skill the average person can become expert, with a little practice and familiarity.
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James R. Davis
Male Administrator
17333 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 02/15/2018 :  12:15 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Absolutely correct. It is THE most important skill a rider can develop.
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