QUESTIONS & ANSWERS

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New Zealand Motorcycle
Safety Consultants,

PO Box 26-036, Newlands, Wellington,
New Zealand
 
Ph 64-4-478-5024
Fax 478-6197

 The Question:
Daniel Giffney wrote
In the carpark that I've been practising in I tend to lock the rear wheel up a lot when doing an emergency stop.
I tend to think that it is because of the surface (that is, smooth, new and tarred), but I have been told otherwise.
Any comments?

Our Answer:
In real life, on many bikes you will get such dramatic weight transfer to the front during emergency braking that the rear wheel will be either off the ground or become so light that locking it up will be unavoidable.

It's obvious that if the rear wheel is off the ground, the front will be giving you 100% of your braking, so learning how not to lock the rear wheel is pretty worthless for that kind of bike anyway.

So you have to learn just how much retardation the rear wheel will give you in an emergency brake on your bike, and the only way to do that is PRACTICE. (You know: Practice, Learn, Live. The more your practice, the more you learn, the more you live.)

What we say to our pupils about back brake use in an emergency is as follows:
"About 85% of your braking comes from the front wheel."

"If you divide your concentration by trying not to lock the rear wheel in an emergency, you are likely to neglect the most important front brake and get much less than 85%, a serious problem in a crash situation."

"If your back wheel locks, you lose about 50% of its braking power. Since it is only giving you about 15% of your braking anyway, you lose (about) 7.5% of your bike's braking power. This still leaves you using 92.5% of your bike's braking ability if the front is used properly but the back is locked."

"If you lock the front wheel because you are not concentrating on using it properly, you lose a major portion of your braking power and are very likely to crash."

"You may be a God and, in a full-blown emergency, be able to control the back brake and prevent rear wheel lock-up while getting the most out of the front brake. Very, very few of us are Gods so we suggest that, in a crisis situation where you encounter that delightful phenomenon known as IQ Dump, go for the front, hit the back and forget about it, concentrating on getting the most from the front."

Failing that, buy a bike with ABS....



The Question:
I was travelling down a 60 zoned road. (literally since it was a downhill) when I spotted a lady and two kids ahead standing by the side of the road.


"Hmm", thinks I. "They look like they want to cross. I wonder if they’ll see me."

Then they started crossing the road. Oh, did I mention there were traffic lights only five metres away, but they didn't wait for them or choose to cross there?

At this point they were on the far side of the road, but I had my eye on them and my hand covering the brake … just in case.

As I get a bit closer the lady sees me and stops.

"Great!", I think.

Now, you all probably know about the point of no-return. That’s the point at which if something pops out at you, there's no way you're gonna stop in time.

Well, guess what... Yep, just as I pass this point, junior decides he'll run across the road...

"$#@!", thinks I as I slam on the brakes. Bike slows down, I increase brake pressure..

"Oops! Too much!" The front end skids and I release pressure slightly.

Now, at this point you're probably thinking, "Hang on, why didn't you swerve?"

Well, it’s a good thing I didn't swerve. Suddenly, Junior sees me, screams his lungs out - and stops.

At this point I'm on the right hand side of the left hand lane. Junior is about in the middle almost to the left of the left hand lane… then he suddenly turns and scoots back the other way! Fortunately, I'm going slow enough that he makes it back and I'm able to putter pass to the left of him.

By the look that was on his face, he'll probably never do it again.

Did I do the right thing? Should you swerve in this sort of situation? I reckon if I had swerved instead of braked, we'd have had kid pancake on the road... as it is, we just have two people with brown pants…

Our answer:
Since you can't swerve under hard braking you have to either decide to swerve or brake. Virtually all riders, when combining IQ Dump with the fact that they are about to hit a little 'un, will go for the brakes rather than trying to swerve.

And as you discovered, this is usually by far the best course of action when dealing with an errant pedestrian.

It's an interesting point whether a blast on the horn helps here as, while it may scatter the pedestrian out of the way, it can also scare the pedestrian so much s/he freezes!

It helps if you have the sort of back tyre that squeals if locked. That noise seems to work on the pedestrians subconscious and they don't freeze but scatter out of the way.

The worst thing is, pedestrian/bike crashes are usually the pedestrians' fault but it's not uncommon for both pedestrian and rider to be killed in them!

Of course, some riders say that when faced with a collision with sheep like pedestrians, if there's more than one, aim for the fattest. It'll absorb the impact better..... J


The Question

Steve wrote
My question is this: How much gravel will it take to low side in a turn, and will you eat pavement with one rock?

Our Answer

The answer is yes and no!

Right, now that I have your full attention...

In some ways, if you hit a road surface hazard in a corner (why didn't you see it, you naughty person you!) then it depends on how you hit it (glancing blow/full on), how far you are leaned over, how well shaped the object is to be kicked out from under your tyre, etc.

The simple truth, as too many experienced riders can tell you, is that anything foreign on the road surface can possibly knock you off when cornering. That's why you scan the road surface carefully as you ride - not directly in front of your front tyre (that's dangerous) but in an in/out movement with the major focus on the Vanishing Point - the very last bit of the corner that you can see.


The Question

Rick Helm wrote
I've a CBR1000FL. I'm getting a high frequency 'tingle' from my left handlebar.Yesterday I took it out for a day run, after an hour it got so bad that it was uncomfortable to keep my hand in place. Gradually it clearly began to affect the nerves in my hand and arm, so it became painful to operate the clutch. In the end it was agony to pull the clutch lever and I could barely keep going - I got to a motorway and headed home, my left hand on my knee!

Our Answer

A high frequency vibration from your bike is not likely to cause the degree of problems you are experiencing.

This leads me to the conclusion that the "high frequency tingle" is actually a physical reaction in your body, almost certainly the result of a bad riding position causing poor blood supply or damage to the nerves.

It is important to realise that what you are getting is probably a type of RSI (Repetitive Strain Injury) caused by the continual movement of muscles etc when the wrist is poorly positioned.

When riding, ensure that your wrists are not bent at an angle (often caused by sitting too far back on the seat). When you are riding the bike, there should be an imaginary straight line running down your forearm across your wrist to your knuckles. The brake and clutch lever should be adjusted appropriately to ensure this. If that imaginary line bends at the wrist, you have a problem!

If this problem keeps occurring you must either do something about it or give up riding. It's as simple as that. RSI is a very nasty injury and can disable you for life!

That's your good news for the day.
J

NB: If it wasn't for the severity of the symptoms you reported we'd suggest you look at the adjustment of your bike's chain and check to see whether a wheel is out of balance, or the back wheel is out of alignment.

Michael Hawkins, an Australian rider, once told us of a similar problem he had with a Ducati ST2. It was his second such bike.

On the first Ducati, the tingle set in after the bike had been in for its 5000km service. Michael assumed the tingle was caused by him holding on too tightly. Then he noticed that while the image in the right hand mirror was fuzzy, the image in the left was clear. So he took the bike back to the dealer.

The dealer's service manager told Michael the vibration was due to "engine harmonics". Unconvinced by this, Michael took the bike elsewhere.

At the next shop it was found that the front wheel needed rebalancing as a weight had fallen off, the back wheel was out of alignment, and the chain was too tight.

Once those problems were corrected, the tingle disappeared, as did the fuzzy image.

On Michael's second ST2, the fuzzy image and tingle set in after the 10,000 service - only to disappear after the chain was adjusted correctly - again by a different dealer.

Michael says he draws two conclusions from this:
- the tingle was related in some way to the chain being too tight.
- the employee who adjusts chains at his Ducati dealer needs educating.


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