This thread appeared on the SabMag list. Merlins
explanation
of why you should use the rear brake is definately
worth
reading.
QUESTION:
From: Honda Sabre and Magna Motorcycle Owners
[mailto:SABMAG@MITVMA.MIT.EDU]On Behalf
Of Phil Ross
Sent: Tuesday, July 18, 2000 4:45 PM
To: SABMAG@MITVMA.MIT.EDU
Subject: Re: Maggot sightings at WIMC;
Mid-O races (long) (fwd)
OK, question time. My feeling is that a stoppie really isn't maximum
deceleration--or is it? Wouldn't a front brake at 3/4 lockup
(vs impending
lockup, which is going to put the tail in the air) together
with the rear
at impending lockup (thus larger contact patch) give you a quicker
stop
than a stoppie? But yet, if you can loft the tail of a VFR with
linked
brakes ... would ABS work any better? Hmmm.
--
Cheers--Phil
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Phil Ross pwr(a)infinet.com
Columbus, OH
AMA#637232 COP#0016 IBA
SS1K, BBG, 50CC
1985 VF1100S V65 Sabre, "The Couch Rocket"
==============================================
ANSWER:
From: Honda Sabre and Magna Motorcycle Owners
[mailto:SABMAG@MITVMA.MIT.EDU] On Behalf
Of Marc W. Mauss
Sent: Tuesday, July 18, 2000 4:49 PM
To: SABMAG@MITVMA.MIT.EDU
Subject: Re: Maggot sightings at WIMC;
Mid-O races (long) (fwd)
The answer is: You're right. I sent the following off-list
the other day.
It explains how and why you're right. BTW, size and number
of
contact areas have NOTHING to do with it.
Let's assume that the total weight of bike and rider is 700 lbs.
Let's assume an initial front/rear weight distribution of 50/50.
Let's assume a coeficient of friction of 1.00 (just to make the
numbers
simple) and that both tires have the same coeficient of friction.
In this situation, before applying brakes, each wheel has 350
lbs of
downward pressure (50% of 700), and therefore (with c of f =
1) will
maintain traction with up to 350 lbs of braking force.
Each wheel will
slip on the road surface (lock up) if MORE THAN 350 lbs
of brakeing
force is applied.
When you start braking, weight is transferred to the front wheel.
You soon reach the point of 60/40 weight distribution -
420 lbs on the
front and 280 lbs on the rear. At this point, (again with
a C of F = 1)
the front wheel can sustain 420 lbs of braking force before
locking up,
while the rear can only handle 280 lbs of braking force.
You then reach a point of 80/20 weight distribution, with the
front whell
bearing 560 lbs and the rear bearing only 140 lbs. At this
point, the rear
wheel can only take 140 lbs of braking force before locking,
while the front
wheel can take 580 lbs of braking force.
By the time you reach a weight transfer of 100/0 (all the weight
on the
front wheel, as in a stopie), the rear wheel will lock with any
braking at
all, while the front can take 700 lbs of braking force before
locking.
At all times, the sum of rear wheel breaking and front wheel
braking is 700 lbs (using the 700 lb weight and a C of
F = 1), but as
more weight transfers to the front, the front wheel gets
more traction,
while the rear wheel gets less.
If you're trying to stop in the shortest possible distance, you
want that
700 lbs of braking force applied until you stop. When you
start braking,
the front can only provide 350 lbs, increasing to 700 by the
time the rear
wheel lifts. But up until that point, you're "wasting"
available braking
traction by not using the rear brake.
Merlin
(formerly Marc W. Mauss)
RRR01
Honorary CSA Consul to Cyberspace
MSF Instructor
Coram (Long Island), NY
'83 Sabre V45 "Just for Fun"
'85 Shadow VT1100C - "Barney" (it's PURPLE)
(hers)
'86 Shadow VT1100C - (hers)
'86 Shadow VT1100C - "Little Wing"
'84 Voyager 1300 - not yet running
Cordura IS a fashion statement.