TEENAGERS ON MOTOR
Dave Williams
-> brake, that I never used the back brake, I.E. not properly utilizing
-> both brakes.
Proper utilization of the back brake is to keep from rolling when
you're at a stop light. Otherwise, you should be able to stop hard
enough to lift the rear wheel clear of the ground, whence it doesn't
matter if you're using the rear brake or not. <grin>
Noemi Berry
> Proper utilization of the back brake is to keep from rolling when
>you're at a stop light. Otherwise, you should be able to stop hard
>enough to lift the rear wheel clear of the ground, whence it doesn't
>matter if you're using the rear brake or not. <grin>
i've heard this argument many times, and it always leaves me with
two questions. i have always wondered why people say they don't use
the rear. ok, so 75% + of your braking is in the front, and max
braking is when you've done a "stoppie". but until the time the
rear wheel leaves the ground, isn't that rear brake contributing to
your stopping? up to 25%? i guess i don't see any reason NOT to
use it, though many people say they don't.
also, i suppose MSF advocates using both for a Good Reason.
at the very least, i don't see any reason NOT to use both.
forgive me for dredging up another cyclical discussion (if this is).
but i've been reading r.m. less than a year and haven't seen this
cycle yet :-).
noemi
-------------------------------------------------------------------------------
no...@cs.ucla.edu KotSBL '82 kawasaki kz305csr dod #443
4580 miles to ride until NM (Next Motorcycle)
reduce traffic: increase your speed
-------------------------------------------------------------------------------
Jonathan E. Quist
>In "A Twist of the Wrist," Keith Code introduces the concept that each
>rider, at any given time, has $10 of concentration, to "spend" on
>whatever they want. Once the $10 is spent, there is no more (ie, human
>concentration is finite).
Unless you have a BMW, in which case you can spend as much as you want,
or a Harley, in which case you've already spent your $10.
--
Jonathan E. Quist INTERACTIVE Systems Corporation
j...@i88.isc.com Naperville, IL
'71 CL450-K4 "Gleep" - "Worth the Oppression"
DoD #094 "I'm not mad; just terribly, terribly hurt." HDM #007
Mark Joseph Andy
[noemi :-) asks about rear brake usage]
I ride on both the track and the street, and I find that I use
different braking techniques for both. On the street (on my Seca) I
tend to use both brakes. I'm almost never stopping with full power,
and use the rear brake to help out and fine tune the front brake. On
the track, I very rarely use the rear brake. The few times I have
have been when I thought that the front wouldn't slow me fast enough.
Also, on the track, usually engine braking is all the rear brake I
need. Also, I'm concentrating on being smooth, while slowing down
fast, and getting to a proper gear, as well as lines, position, etc.
I really don't have time for the rear brake. Now that I'm riding an
RZ on the track (no engine braking), I may modify this a bit, but at
present it seems that there are other areas where I have much more
room for improvement.
Mark
| Mark J. Andy WERA NV #813 AMA #700560 |
| ma...@cmu.edu KotR DoD #813 |
| Co-founder/Rider, Team RISC and Two Geeks Racing |
| '82 Seca 650 (street), '85 RZ350 (track), '78 KM100 (commute-in-snow) |
| I want RZ350 parts like steering damper, fork brace, SS lines, etc... |
Robert Fridman
> > Proper utilization of the back brake is to keep from rolling when
> >you're at a stop light. Otherwise, you should be able to stop hard
> >enough to lift the rear wheel clear of the ground, whence it doesn't
> >matter if you're using the rear brake or not. <grin>
>
> i've heard this argument many times, and it always leaves me with
> two questions. i have always wondered why people say they don't use
> the rear. ok, so 75% + of your braking is in the front, and max
> braking is when you've done a "stoppie". but until the time the
> rear wheel leaves the ground, isn't that rear brake contributing to
> your stopping? up to 25%? i guess i don't see any reason NOT to
> use it, though many people say they don't.
>
Since the rear wheel is offloaded, it looses traction (it only gets
about 25% of the available traction that is) which means it would take much
less force to lock up the rear wheel (about 25% of the force it would take
if rear wheel was not offloaded ;).
As it was mentioned before in this group, a locked up rear wheel will
tend to slide since the traction it experiences is equal no matter which way
it goes. Now, since a sliding rear wheel goes wherever it wants to or
wherever the road and the chassi push it, chances are that it will move
out from the line of motion since the road is not perfectly flat and the
chassi is compressing from the front breaks (ie: fishtail). So if by this
time your heart has not blocked your throat and started asfixiating you, you will
realize that the front wheel is pointing straight ahead (assuming you
countersteer correctly) and the rest of the bike is pointing to the side
while both of you are actually going forward with some speed. Don't forget
that you are on a motorcycle (and not a bicycle) which weighs about 500lbs + you.
Now, if you release the rear brake and the back wheel regains traction, it
will prefere (in fact insist) on traveling along the path of least
resistence, which in this case is to the side remember (since its already pointing
that way). But your front wheel is pointing forward! So as a compromise
between your front and rear tyres, your motorcycle will sort of flip over
and buck you off!
Voilla, you are experiencing a high-side!
The morale of this story is that the rear break does not offer signifficat
stopping power in a HARD stop from speeeeed. The chance of it getting locked
up is so high in a pannic stop that it is not worth risking it. Use the rear
at very low speeds only.
RF.
Martyn J. Wheeler
>Hmmm, $10 bills for concentration and ice cream cones for wheels. Am I
>Mr. Analogy or what? :^)
So how many ice cream cones do you get for $10, and how much of that
goes to the AMA Museum? :-)
--
Martyn
---------...@unx.sas.com----(Martyn J. Wheeler)----DoD #293------------
SAS Institute, Inc: (919) 677-8000 ext.7954 H: (919) 839-0092 (Raleigh, NC)
"If you spin, you deserve to die" -- Mike Hawthorn
"I love competition, but I hate conflict" -- Alain Prost
Kenneth J. Hendrickson
This is such a good idea--I wonder how long it will take before this is
standard on all bikes. I'm a conservative, and I think big government
is bad government, but this is one case where some stinking lawyer might
be able to do some good: pass a law mandating anti-skid brakes (at least
on the front) for all new motorcycles.
--
"Arguing about predestination is virtually irresistible." --RC Sproul
Ken Hendrickson N8DGN/6 k...@usc.edu ...!uunet!usc!pollux!kjh
Chris Malcolm
>>you should be able to stop hard
>>enough to lift the rear wheel clear of the ground, whence it doesn't
>>matter if you're using the rear brake or not. <grin>
>i have always wondered why people say they don't use
>the rear. ok, so 75% + of your braking is in the front, and max
>braking is when you've done a "stoppie". but until the time the
>rear wheel leaves the ground, isn't that rear brake contributing to
>your stopping? up to 25%?
>also, i suppose MSF advocates using both for a Good Reason.
>at the very least, i don't see any reason NOT to use both.
It is true that in good conditions a maximum stop needs only the front
brake, since the rear wheel is on the point of leaving the ground. Now
let us suppose that you are called upon to do a 1/2 maximum stop,
which we _assume_ happens to be a 1/2G, and that under this braking
effort it happens that 60% of the weight is on the front wheel, and
40% on the back. If you stop with only the front wheel you are
retarding one bike weight at 1/2 G with the wheel bearing 60% of its
weight, and consequently require a coefficient of friction of 50/60 or
.83 to stop without losing the front wheel. If you stop with (say)
equal braking on each wheel (this is not the optimum case), then you
will need 25/40 or .63 coeff of friction to stop the back wheel
skidding, and .42 to stop the front wheel from skidding.
So, now let us suppose two bikers braking at 1/2G side by side, one of
them using only the front wheel, and one using 50/50 (non-optimal)
front/rear braking. They are both stopping at the same rate. Then
their wheels encounter a little patch of slightly greasy road with a
coefficent of friction of .8 -- still quite a good value. The biker
using only his front brake goes into a front wheel skid and crashes.
The biker using both brakes still has a safety margin of (.8-.63)/.8 =
21%, and brakes quite safely to a stop.
Now let us suppose that the coefficient of friction actually drops to
.6. The stupid front-wheel-only biker still crashes of course. The
50/50 two-wheel braking biker goes into a rear-wheel skid. These are
easy to control if you are going in a straight line, and he stills
comes safely if excitingly to a stop.
And the third biker, on the Moto Guzzi with linked brakes, didn't even
skid, and didn't even have to think about balancing the braking :-)
In other words, when doing less than the maximum stop, using both
brakes, even distinctly non-optimally, gives you substantially more
safety margin against skidding.
And just recall where you are most likely to find patches of greasy
road? That's right, at halts, where cagers and Harleys :-) like to
leave their mark, not to mention the residue of the occasional
accident.
(And if using both brakes is beyond you, you'ld be a lot safer on a
Moto Guzzi.)
--
Chris Malcolm c...@uk.ac.ed.aifh +44 (0)31 650 3085
Department of Artificial Intelligence, Edinburgh University
5 Forrest Hill, Edinburgh, EH1 2QL, UK DoD #205
John Robert Nadzam
being a lowly undergrad I'll be taking off for the summer, somewhere in
the pennstate area in 2-3days. You can e-mail to me I just wont get it
for 3 months.
see ya in about 6,000 mi
NADZ
DoD #528
Thomas Price
>
> [stuff deleted about the dangers of using the back brake and locking
> it up when it's out of line with the front, and high-siding]
>
>The morale of this story is that the rear break does not offer signifficat
>stopping power in a HARD stop from speeeeed. The chance of it getting locked
>up is so high in a pannic stop that it is not worth risking it. Use the rear
>at very low speeds only.
Jerry, Mojo, anyone, I thought that the MSF answer to this was to
get into the habit of straightening the bike up and getting on both
brakes.
If someone would like to make a reasoned argument that doing so is
not the best thing to do with a modern sportbike (on the street)
I'd like to hear it.
(Additionally, if anyone would like to contradict the MSF flat out, that
might be interesting, although I doubt I'd agree. That is, of course,
presuming that I've correctly represented the MSF's position.)
Tom
PS I skidded my rear wheel in a turn once, but when I hooked up
again, it was very controllable -- probably because I run a Conti
Blitz on the back (ugh!) and it's never sticky enough to flip me :-)
******************************************************************************
tp...@cs.cmu.edu | Mr Ethical | "Tune in, turn on, drop out" - Timmy Leary
1981 KZ440LTD | DoD #518 | "First do no harm" -- Hippyocrates
******************************************************************************
Sean Casey
have? I wonder how small and lightweight it could be. Being able to
simply jam both brakes is an extremely attractive concept. I wonder if
it could be made small enough to fit most bikes?
Sean
--
|``Wind, waves, etc. are breakdowns in the face of the
Sean Casey | commitment to getting from here to there. But they are the
se...@s.ms.uky.edu | conditions for sailing -- not something to be gotten rid
U of KY, Lexington| of, but something to be danced with.''
John Robert Nadzam
my .02$
I dunno, I find my rear brake very useful, Yes I know my front brake
provides the majority of my braking power, but I often use it to help
bleed off speed in corners I've gone into too fast, to help me jockey my
suspension in corners, to sit at red lights and make my rear end bounce
up and down........well,
but yes I have taken the MSF and I do find it very helpful in stopping
quickly.I didn't notice how much I missed that 25% untill recently
(read:now) my rear brake is inoperative due to the fact I think I have
air in the lines somewhere.
NADZ
DoD #528
Dances With Bikers
>This makes me wonder. How much extra hardware does a bike with ABS
>have? I wonder how small and lightweight it could be. Being able to
>simply jam both brakes is an extremely attractive concept.
Attractive perhaps, but a good way to dump it, even with ABS. Because
all current ABS systems work on a lock-release-lock-release cycle, they
ONLY work when the bike is vertical. If you rely on ABS in a corner the
lock-release-lock-release cycle will work more like lock-slide-crash.
Whether the crash is a low side or a high side is left as an excersize
for the student with an ABS bike.
--
Blaine Gardner @ Evans & Sutherland 580 Arapeen Drive, SLC, Utah 84108
blga...@javelin.sim.es.com uunet!javelin.sim.es.com!blgardne BIX: blaine_g
DoD #46 My other motorcycle is a Quadracer. FJ1200
Dave Tharp CDS
>>you're at a stop light. Otherwise, you should be able to stop hard
>>enough to lift the rear wheel clear of the ground, whence it doesn't
>>matter if you're using the rear brake or not. <grin>
>
transfer of weight to the front wheel under racing conditions is close
to 100%. If you watch the GP riders on TV braking at the end of a
straight, light is often seen under the rear tire. Keith Code teaches
his students to ignore the rear brake entirely at the California
Superbike school. The restriction on this technique is that it must be
done with the bike bolt upright, and on smooth, dry pavement. Locking
the front wheel leads to immediate disaster, and in a corner, traction
is shared between cornering forces and braking forces. Therefore, in
racing, braking and gear selection must be done *before* entering a
corner because all traction is spent in cornering forces if you're doing
it right.
>i've heard this argument many times, and it always leaves me with
>two questions. i have always wondered why people say they don't use
>the rear. ok, so 75% + of your braking is in the front, and max
>braking is when you've done a "stoppie". but until the time the
>rear wheel leaves the ground, isn't that rear brake contributing to
>your stopping? up to 25%? i guess i don't see any reason NOT to
>use it, though many people say they don't.
>
On the street, the surface conditions seldom approach a good racetrack,
and your mission does not require maximum cornering speed. The rear
brake must be used in combination with the front brake, particulary on
loose surfaces. Learning to use both brakes to produce best braking
performance under varying road conditions is difficult and only comes
with lots of riding experience. For example, in deep gravel or on sandy
surfaces, the rear brake is much more effective because the front will
wash out immediately (unless, of course, you're on a steep downhill on
one of the above surfaces, in which case either brake with crash you).
Riders with off-road experience have an advantage over street-trained
riders, because they know how to deal with variable surfaces.
>also, i suppose MSF advocates using both for a Good Reason.
>at the very least, i don't see any reason NOT to use both.
>
The MSF folks have the right idea, but they cannot possibly teach all
the necessary techniques of braking in the brief time alloted to them. The
best that they can do is to try to give you some ideas that might keep
you alive during the time in which you are gaining experience.
>no...@cs.ucla.edu KotSBL '82 kawasaki kz305csr dod #443
Oh, you might add '55-'69 BMW 500 and 600cc twins to the SBL. They're
kickstart only, but are incredibly easy. And the seat height is
adjustable on the solo saddle down to about 27".
-----------------------------------------------------------------------------
| Dave Tharp | DoD #0751 | "You can't wear out |
| da...@loowit.WR.TEK.COM | MRA #151 | an Indian Scout, |
| '88 K75S '48 Indian Chief | AHRMA #751 | Or its brother the Chief.|
| '75 R90S(#151) '68 CB450(#751) | AMA #524737 | They're built like rocks |
| '65 R50/2/Velorex '57 NSU Max | | to take the knocks, |
| | (Compulsive | It's the Harleys that |
| My employer has no idea. | Joiner) | give you grief." |
-----------------------------------------------------------------------------
Jonathan E. Quist
>Is a Moto Guzzi the *only* motorcycle with anti-skid brakes?
>
>This is such a good idea--I wonder how long it will take before this is
>standard on all bikes. I'm a conservative, and I think big government
>is bad government, but this is one case where some stinking lawyer might
>be able to do some good: pass a law mandating anti-skid brakes (at least
>on the front) for all new motorcycles.
You never heard of a small manufacturer by the name of "BMW"?
And no, this would not be a good thing a law required anti-lock brakes
(there's no such thing as anti-skid, no matter what they tell you) on
only the front wheel. Might actually cause more accidents then it
would prevent. You need the ABS on the rear, for stability. If you
lose braking traction on the rear, but still have good braking traction
on the front, the rear end get's envious and decides it wants to be
in front instead. That's why there is a law requiring rear ABS on some
vehicles (like passenger vans, which have brakes designed to handle
max gross weight, but spend most of their time near empty weight, making
wheel lockup much more likely).
Technical issues aside, there are some of us who _like_ to be permitted
to control our machines; some who occaisionally want to lock a rear wheel
to break the rear end loose.... and some of us who are simply willing
to accept the responsibility of learning our limits and staying within them.
David Svoboda
|The biker
|using only his front brake goes into a front wheel skid and crashes.
Just a small point: a front wheel skid != a crash. I suggest that if you
find yourself terrified by skidding the front, take a ratbike out in the
rain and learn how to do it. Just because you lose stability for a
moment doesn't mean you can't regain it the next (let off the damn brake,
okay? :-), and a front skid doesn't cause a highside. It's not
comfortable, exactly, but you don't have to crash, either.
I dropped my beloved Connie twice, emergency braking in the rain, before
I said "screw it", and practiced sliding with her. (Those double disks are
*powerful*.) I haven't made a braking mistake since. And, of course,
there are the slippy-slide sessions with the ratbike on an icy parking lot
in the middle of the winter. (Wear armor, and don't care about the bike. :-)
Don'cha just hate it when ya drop a new bike before ya make the first
loan payment? :-(
Dave Svoboda (ru...@gagme.chi.il.us) | An Angel on a Harley pulls
90 Concours 1000 (Mmmmmmmmmmmm) | across to greet a fellow
81 KZ550 Rat (The Little Engine That Could) | Rolling Stone.
AMA ...let me get it out..oh yes... 583905 | He says, "Where ya been,
DoD #0330 "LtF,FtL Geeks R Us" | where ya 'goin?" -- R Waters
Ed Green - Pixel Cruncher
> Therefore, in
>racing, braking and gear selection must be done *before* entering a
>corner because all traction is spent in cornering forces if you're doing
>it right.
To pick a nit, on the street, braking and gear selection should be done
before entering a corner, also.
>On the street, the surface conditions seldom approach a good racetrack,
>and your mission does not require maximum cornering speed.
OTOH, on the track, unexpected hazards never approach those on the
street. Since emergency straight-line braking is often necessary on
the street, seldom with any warning (unlike entering a turn on the
track), using the technique best suited to that, for all one's braking,
reenforces the technique, and the skill with which it can be applied.
IMHO, that technique is 100% concentration on the front, including
letting off when it starts to slide.
---
Ed Green, former Ninjaite |I was drinking last night with a biker,
Ed.G...@East.Sun.COM |and I showed him a picture of you. I said,
DoD #0111 (919)460-8302 |"Go on, get to know her, you'll like her!"
(The Grateful Dead) --> |It seemed like the least I could do...
Tim Keller
>will prefere (in fact insist) on traveling along the path of least
>resistence, which in this case is to the side remember (since its already pointing
>that way). But your front wheel is pointing forward! So as a compromise
>between your front and rear tyres, your motorcycle will sort of flip over
>and buck you off!
>
>Voilla, you are experiencing a high-side!
>
>The morale of this story is that the rear break does not offer signifficat
>stopping power in a HARD stop from speeeeed. The chance of it getting locked
>up is so high in a pannic stop that it is not worth risking it. Use the rear
>at very low speeds only.
>
> RF.
the front brake and the rear wheel is locked, you have three forces: the front
braking force, the rear tire sliding force, and your momentum acting through
the center of gravity of the bike (above the wheel axis). When the rear tire
slides to the side your cg shifts out of line with the front tire, and the
only thing preventing you from "passing" your front tire is the force exerted
by the sliding rear wheel. When you release the rear wheel, there is no longer
any force opposing this "passing" effect. Your cg is now to one side of the
bike and instead of your momentum compressing the front forks as it would if
your cg was in line with the front tire, it simply pivots the bike around the
steering column and the front axle. Thus the "bucking" effect, and a rather
unpleasant feeling of freedom from the bike.
I suppose you could argue that by releasing the front brake you might
be able to unlock the rear wheel, but something tells me you'll crash either
way. Maybe that's why the MSF instructors told us to keep that rear wheel
locked once you lock it.
Tim,
Charlie Preston
It sounds almost like the buses in this area. It especially effective for
warning pedistrians and drivers who have windows open.
David H. Wise
>>you're at a stop light. Otherwise, you should be able to stop hard
>>enough to lift the rear wheel clear of the ground, whence it doesn't
>>matter if you're using the rear brake or not. <grin>
>
>i've heard this argument many times, and it always leaves me with
>two questions. i have always wondered why people say they don't use
>the rear.
Me too. Even though I can get by using only the front (or only the rear!)
the majority of times I brake, I always use both to keep in practice. That
one time when maximum braking can save your life, you'd better do it right.
Both wheels at impending skid for the entire duration of the maneuver. You
just can't stop quicker than that.
> ok, so 75% + of your braking is in the front, and max
>braking is when you've done a "stoppie".
Unless your bike doesn't do stoppies. Lots of bikes lock the front wheel
first.
> but until the time the
>rear wheel leaves the ground, isn't that rear brake contributing to
>your stopping? up to 25%? i guess i don't see any reason NOT to
>use it, though many people say they don't.
>
>also, i suppose MSF advocates using both for a Good Reason.
>at the very least, i don't see any reason NOT to use both.
The front/rear ratio varies with time. When you start to brake,
the rear wheel still has a lot of weight on it. As the forks compress,
some of that weight shifts to the front, and you can increase front
braking force if you want, but you _must_ decrease rear braking force.
To get the most braking, this is a delicate balancing act and needs
mucho practice, and it's different for every bike.
>
>forgive me for dredging up another cyclical discussion (if this is).
>but i've been reading r.m. less than a year and haven't seen this
>cycle yet :-).
I use the metaphor of a blender with a small outlet at the bottom. Sure,
you keep throwing new things in the top, but most of the stuff inside goes
round and round quite a few times before it leaves.
>noemi
>-------------------------------------------------------------------------------
>no...@cs.ucla.edu KotSBL '82 kawasaki kz305csr dod #443
> 4580 miles to ride until NM (Next Motorcycle)
> reduce traffic: increase your speed
>-------------------------------------------------------------------------------
--
--
David Wise (DoD#427, dav...@orca.wv.tek.com, Packy -- 1980 CX500C)
Dave Tharp CDS
Yes, it's the only bike whose brakes are so bad that they cannot be
locked, and which has so little power , the rear tire cannot be spun.
>
>This is such a good idea--I wonder how long it will take before this is
>standard on all bikes. I'm a conservative, and I think big government
>is bad government, but this is one case where some stinking lawyer might
>be able to do some good: pass a law mandating anti-skid brakes (at least
>on the front) for all new motorcycles.
>
>--
least as much sense as this post.
Dave Tharp CDS
>This makes me wonder. How much extra hardware does a bike with ABS
>have? I wonder how small and lightweight it could be. Being able to
>simply jam both brakes is an extremely attractive concept. I wonder if
>it could be made small enough to fit most bikes?
>
battery. The big hydraulic actuators are the main problem. The pickups
consist of gear-like gismos on the wheels and what appears to be a
reluctance coil on the brake mounts. The computer box is under the
seat. The rear actuator is behind the right footpeg, and the front is
buried under the tank behind the radiator.
Martyn J. Wheeler
>Is a Moto Guzzi the *only* motorcycle with anti-skid brakes?
>
>This is such a good idea--I wonder how long it will take before this is
>standard on all bikes. I'm a conservative, and I think big government
>is bad government, but this is one case where some stinking lawyer might
>be able to do some good: pass a law mandating anti-skid brakes (at least
>on the front) for all new motorcycles.
A couple of points:
1) Moto Guzzis do not have "anti-skid" (by which I assume you mean
anti-lock) brakes, they have linked brakes. So do Goldwings and (I
think) a few others. What this does is to operate the rear brake disc
and one of the front discs with the foot pedal, and the remaining
front disc with the hand lever. You can still lock up the brakes if
you stab them.
2) Lawyers are the reason we *didn't* get anti-lock brakes in the US
until BMW, then Honda & Yamaha, were brave enough to say "stuff the
product liability suits." Putting safety improvements on some bikes
in your line and not others is tantamount to admitting you make some
unsafe bikes, at least in US law.
Anyway, (I suppose this is a third point?) you only *need* anti-lock
brakes if you are deficient in braking skills. What about the Honda
TCS -- should that be mandatory? I assume you ride an ST1100, because
it's the only safe bike? I suppose you would also support passing a
law installing governors on bikes so they can't exceed the national
speed limit? Brakes are still limited by the laws of physics, which
(simplified) say "you can't brake really hard while leaned over."
Law student, are you? :-)
S.Fielding-Isaacs [WWFO Eng Wordsmith]
>In article <1992May14....@cs.ucla.edu> no...@maui.cs.ucla.edu (Noemi Berry) writes:
>>
>>> Proper utilization of the back brake is to keep from rolling when
>>>you're at a stop light. Otherwise, you should be able to stop hard
>>>enough to lift the rear wheel clear of the ground, whence it doesn't
>>>matter if you're using the rear brake or not. <grin>
>>
>>i've heard this argument many times, and it always leaves me with
>>two questions. i have always wondered why people say they don't use
>>the rear.
>
>Me too. Even though I can get by using only the front (or only the rear!)
>the majority of times I brake, I always use both to keep in practice. That
>one time when maximum braking can save your life, you'd better do it right.
>Both wheels at impending skid for the entire duration of the maneuver. You
>just can't stop quicker than that.
Yet Another Cyclical Argument (YACA).
Until recently, I was of the "use only the front brake" school of thought.
I have years of experience riding modern sportbikes and racing. I firmly
believe that in a panic situation, using only the front brake is the
correct action. By definition, one only has split seconds to react
(because if one were prepared, one wouldn't be in a panic situation, would
one? :->). In this sort of situation, those actions which we have
practiced and mastered will go a long way to saving us. In this case,
the full-bore stop with the front brake.
I would venture to say that 95% or better of street riders don't know
the limits of their front brake. Consequently, they use it timidly or
not to its full capacity. The only way around this is to practice
high-speed and low-speed full-bore stops.
Even after you have mastered this skill, you still have to worry about
processing what is happening around you, choosing which one of your
escape routes will keep your ass intact, and making sure that no one
else is going to clean your clock while you execute your avoidance
maneuver.
Lots and lots to think about, while your adrenaline is kicking in,
and you are trying to hold that front brake at impending lockup and
keep your weight positioned so that you can move the bike rapidly.
You have NO time to waste. No concentration to waste on the rear brake.
Some argue (the MSF proponents out there) that practice makes a big
difference, that you get better braking from using both brakes.
I would argue in response that this is in a test-bed condition.
Real life really agrees so nicely with the test strip. It is near
impossible to simulate the rush of adrenalin (unless you want to
dig up that inhaler :->) that you get when your life is threatened.
I think it evident that the vast majority of people would have a
great deal of difficulty writing their name intelligibly after
such an incident. It is too much to ask of the average rider that
s/he feather the rear brake in proportion to the weight shift
(so as to prevent rear wheel lockup). It's just not going to happen.
Most riders will just jump on that rear brake and lock the rear,
unable to steer the bike with any confidence.
>> ok, so 75% + of your braking is in the front, and max
>>braking is when you've done a "stoppie".
>
>Unless your bike doesn't do stoppies. Lots of bikes lock the front wheel
>first.
>
>The front/rear ratio varies with time. When you start to brake,
>the rear wheel still has a lot of weight on it. As the forks compress,
>some of that weight shifts to the front, and you can increase front
>braking force if you want, but you _must_ decrease rear braking force.
Having said all I have said above, I rode my old roommates Beemer.
What a piece of junk (R75/6 I think). Front brake was a total joke.
Just had to use the rear brake a lot (while carrying a passenger).
Seemed like it didn't have a hope in hell of lifting the rear under
braking (and it was in good to excellent mechanical condition).
So I suppose that I must narrow the focus of my comments/statement
above. If your bike is anywhere near a modern sportbike I think
you should be using the front brake to the exclusion of the rear.
Point being that a well-used front brake will outperform a poorly
used front and rear brake combination.
However, in the event that you ride a bike with a less than optimal
weight distribution I can see that one would have to make the
best of a bad situation and use the rear brake. I think the
MSF comments are pertinent here. I think that they should consider
revising their curriculum in the light of advances in technology
and construction of bikes. Also keeping in mind that test-bed
conditions to not approximate the reactions of riders in real-life
crises.
--
Stefan Fielding-Isaacs me: (415) 599-4876 me at them: (415) 688-9400
dba Live-Wire Technologies (a consulting technical writing firm)
AMA/CCS #5, Regional Lightweight Supersport, Superbike, Grand Prix Champion
mail: race-r...@formula1.Corp.Sun.COM to join motorcycle roadracing list
Noemi Berry
>the rear wheel still has a lot of weight on it. As the forks compress,
>some of that weight shifts to the front, and you can increase front
>braking force if you want, but you _must_ decrease rear braking force.
but WHY?! (said the annoying five-year-old repeatedly)
not that i don't believe you, but i don't understand why holding that rear
brake will make any difference. provided you were to use the front
brake with maximum effectiveness (not always a given, i know), why
must you _decrease_ rear braking force? at the very worst, won't
it just become ineffective as the forks compress and weight is shifted
forward, or will it truly hamper the front braking?
a lot of answers to the rear-brake-usage question have gone by, including
$10 allocation of concentration (Code's method, a la Ed Green), "because
if you lock the rear and release it you high-side" (not exactly an
*answer*!), because MSF says so, because it's not useful on the racetrack
... the usual DoD consensus! :-)
i am inclined to agree with MSF about using both, but learned
a lot from going on a rear-brake "diet" for 2 weeks, that is,
only using the front. i learned that i was getting a LOT more
braking from the rear than i thought (in a normal street situation)
(hence my question about why people say they don't use it), and
that i was cheating with the rear to create the illusion of smooth
front braking, and that really, my "front braking technique" is
an oxymoron.
and so i find myself in MSF:RSS to get the very basics in (again),
more for braking technique than anything. just in time -- before
my experience level tips over into the "i know what i'm doing"
skepticism, and out of the beginner's "tell me more, fill me
with knowledge O Great Ones" open mind. :-)
>I use the metaphor of a blender with a small outlet at the bottom. Sure,
>you keep throwing new things in the top, but most of the stuff inside goes
>round and round quite a few times before it leaves.
heh heh.
noemi
-------------------------------------------------------------------------------
no...@cs.ucla.edu KotSBL '82 kawasaki kz305csr dod #443
4440 miles to ride until NM (Next Motorcycle)
Mark Slagle
[...a lot of hand-waving arguments for front brake only...]
> and construction of bikes. Also keeping in mind that test-bed
> conditions to not approximate the reactions of riders in real-life
> crises.
When I was up in BC a few years ago, riding at an extremely high
rate of speed between Prince George and Jasper (daylight til around
11pm, neat), a good sized elk dashed into the road in front of me
and grew roots when he saw me. I got on both of my brakes hard,
let up some on the back one, and had the front tire howling like
a banshee all the way down to about two or three miles an hour.
At this point I was about fifteen feet from the beast who, seeing
that I was just some speed-crazed hoodlum on a motorcycle, lost
interest and pranced off into the woods. Heaving a great sigh
of relief, and rushing like a freight train on adrenaline, I
forgot to put my feet down. The stories about adrenaline strength
must be true, because I eventually got a foot off the peg and
onto the pavement and caught the bike and hauled it back from
about thirty degrees lean without more than a grunt. Of course,
I then almost dropped it over the other side from the momentum
and vertigo, but soon was able to negotiate it over to the side
of the road and onto the side stand whereafter I hyperventilated
and thanked all the deities I could think of until I got back on
the mellow side of my self.
So what's the point of this ramble? Well, I was about fifteen
feet from becoming an antler ornament for an animal about as
big as a good sized, ten-year old Cadillac Coupe de Ville. It
is my contention that if I hadn't used both brakes, I would now
be road kill in the middle of nowhere Canada where the pavement
never wears out. If I hadn't taken the time and effort to practice
panic stops over the years, I would not have the great pleasure of
regaling you all with this tale (some would no doubt find that an
improvement, but I will stubbornly disagree). So don't give ME
that crap about real life not being unlike test conditions. Sure
it's different: In the test you don't die if you fuck it up.
That's the difference. But the brakes still work best when you use
both. You use only one if you want, but I want to stop before
planting my face in elk intestines.
--
----
Mark E. Slagle PO Box 61059
sla...@lmsc.lockheed.com Sunnyvale, CA 94088
408-756-0895 USA
Mark Slagle
> not that i don't believe you, but i don't understand why holding that rear
> brake will make any difference. provided you were to use the front
> brake with maximum effectiveness (not always a given, i know), why
> must you _decrease_ rear braking force? at the very worst, won't
> it just become ineffective as the forks compress and weight is shifted
> forward, or will it truly hamper the front braking?
As you apply the brakes the weight of the bike shifts to the
front wheel. The reduced weight on the back wheel causes it
to be more inclined to lock up and skid. When the back wheel
is sliding already it has the unpleasant tendency to slide
sideways as well as in the direction of travel. This is due
to the condition of being in a state of unstable equilibrium
with respect to the hinge at the front forks, sorta like trying
to hold a pendulum upside down. You can do it, but it's not
easy and requires constant corrections to keep it there. This
distracts from the task at hand, which is not hitting some
obstacle in your path.
Now, not only does having the rear wheel out to the side make
it a hell of a lot more difficult to stop (and it takes farther),
the rear wheel also has the disconcerting tendency to grab the
pavement abruptly if you let off the rear brake when it is out
there. This causes the unwary rider to do a Superman imitation
over the "high side". Speaking from experience, this is only
enjoyable for the first few moments. Upon performing an expert
three point landing on the pavement, the experience becomes
somewhat less delightful thereafter. You may confirm this
information for yourself if you wish, although I do recommend
against it.
Michial Gunter
>The front/rear ratio varies with time. When you start to brake,
>the rear wheel still has a lot of weight on it. As the forks compress,
>some of that weight shifts to the front, and you can increase front
>braking force if you want, but you _must_ decrease rear braking force.
The main reason the force at the front tire increases (and the force
on the rear decreases) is that the bike is attempting to rotate about
its center of mass:
\ _
\ \
---------------- ---> | (Rotation about the center of mass.)
| | /
| X | <--
xxx ^ xxx
x x | x x
x x | x x
x x | x x
<---xxx | <---xxx
|
|
Center of Mass
Try braking hard on a bicycle. No compression of suspension (unless your very lucky)
but the amout of force on the tires shiftes. In fact a bicycle is a
good place to practice maximum braking (and the only one I have at the moment:-(().
not that i don't believe you, but i don't understand why holding that rear
brake will make any difference. provided you were to use the front
brake with maximum effectiveness (not always a given, i know), why
must you _decrease_ rear braking force? at the very worst, won't
it just become ineffective as the forks compress and weight is shifted
forward, or will it truly hamper the front braking?
As the amount of down-force at the rear tire decrease, you better
decrease the force you expect it to exert to slow the bike down,
or it will do it for you (by sliding.)
LF @ C * DF
C = Coefficient of friction
(fixed for a given tire and surface --- that is, not fixed enough)
LF = Lateral force
DF = Downward force
Friction comes in two flavors: static and sliding. Static is
higher is all cases and is much higher for a tire.
You don't slide as long as @ is <=. When that is not the case the
back tire is going to slide causing a drastic decreases in the amount
of available stopping power there as well as the more troublesome
problems of the rear sliding out of line with the front.
mike
Mike Coleman
[about practicing front wheel skids]
I was intrigued by this, so I did a little playing with it in the parking lot
a few minutes ago. In runs starting at about 15-20mph, I applied either the
front or the rear brake and was able to lay long skids without any feeling of
side-to-side instability. Front skids were more unnerving because the front
end would start "chattering" (vibrating heavily) when the wheel hit a
less-slick spot. I should add that the concrete in the parking lot was very
smooth, making skidding easy.
Mike
--
--Mike Coleman (col...@cs.ucla.edu), Ringmaster, Boelter Hall Roach Circus--
It could be worse--you could be bicycling in Florida.
Dances With Bikers
>>Is a Moto Guzzi the *only* motorcycle with anti-skid brakes?
> ^^^^^^^^^^^^^^^^
>Yes, it's the only bike whose brakes are so bad that they cannot be
>locked, and which has so little power , the rear tire cannot be spun.
For heaven's sake, don't let Mike Tiberio know about this, he's been
doing pretty well racing one of the beasts. :-)
Al Bowers
>>The front/rear ratio varies with time. When you start to brake,
>>the rear wheel still has a lot of weight on it. As the forks compress,
>>some of that weight shifts to the front, and you can increase front
>>braking force if you want, but you _must_ decrease rear braking force.
Actually, it varies as a function of wheel loading and braking force.
time is only because there is a time constant in the raction to the
forces applied.
>but WHY?! (said the annoying five-year-old repeatedly)
A thought experiment. If you *SLAM* on the front brake, the wheel
locks and you go down. Now, if you apply progressivly more and more
front brake pressure, the forks compress, the front wheel loads up and
you can achieve higher front brake lever force without locking the
front wheel (with control) than if you simply jerked on the lever and
locked the wheel. The reason is that with the additional load of the
weight shift, the wheel could continue to turn the brake with that
amount of braking. Without the weight shift, there wasn't enough
available traction to keep the wheel turning.
>not that i don't believe you, but i don't understand why holding that rear
>brake will make any difference. provided you were to use the front
>brake with maximum effectiveness (not always a given, i know), why
>must you _decrease_ rear braking force? at the very worst, won't
>it just become ineffective as the forks compress and weight is shifted
>forward, or will it truly hamper the front braking?
Now as the weight shifts forward, you have less available traction at
the back. So ease up on the rear.
>a lot of answers to the rear-brake-usage question have gone by, including
>$10 allocation of concentration (Code's method, a la Ed Green), "because
>if you lock the rear and release it you high-side" (not exactly an
>*answer*!), because MSF says so, because it's not useful on the racetrack
>... the usual DoD consensus! :-)
The most important thing that the MSF emphasizes is that using both
brakes is best. The reason they do this is the result of the data
from the Hurt report. Now, here is where the divergence of opinion
occurs. Both the MSF and Code/CLASS/whoever-racer are right. The
reason has to do with the equipment being used. No matter how hard
you try, you will find it impossible to do a stoppie on a Goldwing
Aspencade. In this case, there is still a significant portion of the
weight being carried by the rear wheel. In this case it is a very
good idea to use the rear brake, balanced with the front (the front
will still carry more braking). Most modern sportbikes carry so much
weight bias and have such exceptional brakes that _lifting_ the rear
wheel off the ground in a all-out-front brake only stop that use of
the rear brake is _entirely_ superfluous. Cruisers likewaise have
their own requirements.
Now here is where it gets sticky. You never know when you will be
confronted by a brain-dead cager attempting to make you and their door
handle occupy the same point in the time-space continum. You might be
solo on your GSXRZFJFZRVFR whatever. And in this case, if that is the
only way you ride, you'll possibly do the correct thing (provided you
_know_ what the right thing is to start with). If you are out on your
first ever ride on a XLH after learning to ride on a G00F2, you'll
probably have a problem cause you didn't use enough rear brake. On
the otherhand, if you've just gotten off of a KZ1300, and are getting
familiar with a ZX-6, you have the converse problem.
>i am inclined to agree with MSF about using both, but learned
>a lot from going on a rear-brake "diet" for 2 weeks, that is,
>only using the front. i learned that i was getting a LOT more
>braking from the rear than i thought (in a normal street situation)
>(hence my question about why people say they don't use it), and
>that i was cheating with the rear to create the illusion of smooth
>front braking, and that really, my "front braking technique" is
>an oxymoron.
In this case, you have your particular machine well dialed in and
understand that a dual brake usage is suited to it. This is *A GOOD
THING*. If you tried this same experiment on a sportbike, you'll find
that there isn't too much difference. Or, conversely, if you try it
on a cruiser you'll find that a lot of rear brake is required to
optimaize your stops.
>and so i find myself in MSF:RSS to get the very basics in (again),
>more for braking technique than anything. just in time -- before
>my experience level tips over into the "i know what i'm doing"
>skepticism, and out of the beginner's "tell me more, fill me
>with knowledge O Great Ones" open mind. :-)
:-) indeed. But always being open to ideas and discovering what works
best is a good attitude to have. Especially, if you are doing
something unfamiliar. And that can be something as simple as new
tires on your old bike, or a different bike, even of the same model.
Who knows, the brake pads might be different and react different
compared to what you are used to.
So not only does the style of what you ride affect the way you
approach problems, but the differences in equipment also should affect
you approach. You must adapt to your surroundings. And you should
try not to adapt to the brain-dead cager's door handle. IMHO.
Safe riding.
--
"Hokey religions and ancient weapons are no match for a good blaster
at your side, kid." - Han Solo, Star Wars
Al Bowers bow...@rigel.dfrf.nasa.gov
Iaido Takamine Hobie 16 Rossignol Alfa GTV6 Ducati MHR DOD #900