Stopping distance Bike Vs Car

Andy Bonwick · Dec 7, 2006

Of course you can't.
"The hardest you can brake is just before the rear wheel leaves the ground."
Is that better?
Click to expand...

That sounds right to me.

steve auvache · Dec 7, 2006

Andy Bonwick wrote

Ask the OP who made the statement.
Click to expand...

OK then.

Oi Bonwick!!

Is your bike a shaftie or is it chain driven?

Andy Bonwick · Dec 7, 2006

Andy Bonwick wrote

OK then.

Oi Bonwick!!

Is your bike a shaftie or is it chain driven?
Click to expand...

Both.

Scraggy · Dec 7, 2006

TOG@toil wrote:

What impresses me, now that I've got a bike with ABS[1], is just how
hard one can brake in wet conditions. I haven't cut the ABS in yet.

[1] I presume it's working.
Click to expand...

Chaps may find this interesting:

Lifted from BMW Club Mag, who lifted it from Motorad.
ABS comparison 100kph dists in meters.

Bike Dry Poor Wet Wet
Road Surface Variable
R1200R 37.4 42.9 43.0 58.0

K1200S 39.8 46.8 40.9 58.5

F800S 40.7 48.9 44.2 53.0

KTM990
Adventure 41.8 48.1 46.4 58.0

CBF1000 43.0 49.1 44.1 59.9

Duc ST3s 39.3 51.5 46.6 60.5

Varadero 40.7 49.2 44.8 63.5

VStrom650 41.6 52.5 44.8 63.3

Sprint ST 44.0 52.0 45.1 63.1

ZZR1400 41.7 52.6 45.0 69.0

FJR1300A 49.1 54.4 50.3 69.4

There are various notes and comments on some of the bikes, which, if
anyone's interested I'll put up.

Ben · Dec 7, 2006

In my motorcycle training course this summer, after we had all practiced
emergency stops from 50kph, the instructor did the same in his car, and
stopped in about 2/3 of the distance the best had managed on bikes. The car
was a Mercedes SLK, though.
Click to expand...

And the bikers were, presumably, all novices. Proves nothing.

What impresses me, now that I've got a bike with ABS[1], is just how
hard one can brake in wet conditions. I haven't cut the ABS in yet.
Click to expand...

I know from checking that my car[1] requires less braking distance
than my GSXR1000. I've tested this into the same roundabout at the
same speed. Four big fat tyres and ABS really help.

Admittedly, it takes a lot less skill to simply stand on the brakes in
the car so it might just be me being crap on the bike.

[1] http://www.ford.co.uk/ie/fiesta/-/fie_0508_body_st/-/-/-/972031

Beav · Dec 7, 2006

Wobble said:

Excuse my ignorance.
"legs feel"?
Click to expand...

Look to your nick.

--
Beav

VN 750
Zed 1000
OMF# 19

Beav · Dec 7, 2006

Dr Ivan D. Reid said:

But mass balances out in the equations:

F=m*a; F_max=m*g*CoF => a_max=g*CoF where F is force of braking, a is
deceleration, g is gravitational acceleration "constant" and CoF is
coeeficient of friction. i.e. maximum braking force is a function only
of the CoF of the tyres, not the mass.

What Eiron is arguing is that it's more likely that a bike's rear
wheel will start to lift before a_max is achieved. If the CofG is
distance
r away from the front axle, at an angle th from the horizontal, the
potential
torque backward along r is m*g*cos(th)*r. The torque forward from the
braking force is F*(horizontal distance of CofG above axle) = F*r*sin(th).
Note that because of the behaviour of sin and cos around zero, the torque
from the mass is always backward while the torque from braking is forward
for
th>0 (CofG above axle) and backward for CofG below axle -- obviously if
the CofG is below the axle the vehicle dips rather than rises under
braking.

The rear wheel will start to lift when the two torques balance
(assuming CogG above axle) i.e. m*g*cos(th)*r = F*r*sin(th) =
m*a*r*sin(th)
or g*cos(th) = a*sin(th) i.e. a=g/tan(th); Since tan(th) is monotonic
with
th, the larger th, the larger tan(th) and the lower the value of
deceleration
a which will cause the CofG and thus the rear wheel(s) (assuming a rigid
chassis...) to lift.

Now I've got to get back to my Boosted Decision Trees and Gene
Expression Programming. Play nicely, kids.
Click to expand...

And I've got to go and have a lie down

--
Beav

VN 750
Zed 1000
OMF# 19

Ace · Dec 8, 2006

<folds>
Click to expand...

You have a collar-bone that you can fold? Wow, that beats me hands
down.

--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ GSX-R1000K3 (slightly broken, currently missing)
`\\ | //' BOTAFOT#3, SbS#2, UKRMMA#13, DFV#8, SKA#2, IBB#10
`\|/`
`

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