Braking Distance of Cycles

In message
, at
17:05:48 on Mon, 16 Aug 2010, thirty-six
remarked:
There are no figures, each machine and person is individual, the
advice is to never go so fast as you cannot stop within the distance
you can see to be clear on your own side of the road. This takes
account of machine, rider and conditions which are all VARIABLE.

Including whether it's uphill or downhill; which by observation has a
much more significant effect upon cycles than motor vehicles.
--
Roland Perry

In message , at 08:56:37 on Tue, 17
Aug 2010, Nick Maclaren remarked:
It would be
quicker to dispense with the brakes and just go Flintstone style.

As I have just posted, the 34% figure is due to loss of control, and
is accurate for many (or even most) cyclists. You aren't going to
reduce that, HOWEVER efficient your brakes are. It may be as high as
50% if you ride in a deep crouch with your knees around your ears,
and is higher for a recumbent, or with heavy weights in rear panniers,
of course.

To what extent are cyclists with a child on a seat, or in a trailer
behind, inhibited from doing an "emergency stop" because of the effect
it might have in unseating their passenger?

I won't even mention those cyclists with a bag of shopping hanging from
each side of the handlebars.
--
Roland Perry

In message , Roland Perry
writes
In message , at 08:56:37 on Tue, 17
Aug 2010, Nick Maclaren remarked:
It would be
quicker to dispense with the brakes and just go Flintstone style.

As I have just posted, the 34% figure is due to loss of control, and
is accurate for many (or even most) cyclists. You aren't going to
reduce that, HOWEVER efficient your brakes are. It may be as high as
50% if you ride in a deep crouch with your knees around your ears,
and is higher for a recumbent, or with heavy weights in rear panniers,
of course.

To what extent are cyclists with a child on a seat, or in a trailer
behind, inhibited from doing an "emergency stop" because of the effect
it might have in unseating their passenger?


IME, it doesn't make a lot of difference, if anything, a child in a rear
mounted seat improves matters as you have more weight where you want it
over the rear wheel. Yes, it is high up, but it's also further back,
which makes a big difference. Even just moving your weight back by
slipping off the back of the saddle helps.

Re trailers, it seems to depend where the trailer mounts to the bike.
I've a cargo trailer that mounts to the top of the seat tube. Under
braking there is a tendency for it to reduce the downward force on the
rear wheel. In general use it doesn't seem to make a difference, but I
have had situations with it heavily loaded (say 50- 80kg) braking hard
on moderate downhill where it did lift the rear wheel.

I've a kiddie trailer that mounts to the rear axle. This doesn't seem to
cause any issues at all.

I won't even mention those cyclists with a bag of shopping hanging from
each side of the handlebars.

They always have the possibility of extra emergency braking from the
bags and the front wheels.
--
Chris French

**** off.

**** off.

snip

On Aug 17, 9:59*am, "David" wrote:
**** off.

Now there is a good debating style (not)!

"Derek C" wrote in message
Now there is a good debating style (not)!

I wasn't debating (much like you on all of your posts.).

Nick Maclaren wrote:

I have used drum brakes, which are largely unaffected by wet. As
Bicycling Science points out, an upright cyclist will go over the
handlebars at 0.5-0.7 g, depending on the bicycle, rider and style.
However, that DOESN'T mean that you can brake at that, safely,
because a bicycle becomes uncontrollable when the weight on the rear
wheel reduces enough that it starts to skid. A maximum safe
deceleration of 0.35-0.5 g is a reasonable figure, comparable with
the Highway Code level of conservatism.


Not true, a bicycle is perfectly controllable and you can brake right up
to the point where the rear wheel has lifted clear of the ground.
Cyclists can do it and you will see motorcyclists doing it too (known as
a stoppie)
http://en.wikipedia.org/wiki/Stoppie

Like skid control in cars and many other things related to
driving/riding its a massive advantage if you've practised first outside
of an emergency first to get it right. Otherwise you risk either having
to let go of the brakes or go over the bars if you can't balance the
braking with the rear wheel lift.

Before I fitted the rear wheel clip on my Brompton I twice braked hard
(pedestrians stepping out, one on the steep downhill of Park St in
Bristol in the wet) and ended up both times with the rear wheel folded
under when I had come to a stop. That couldn't have happened if I had
been braking at less than the speed which lifted the rear wheel
substantially off the ground. I really recommend cyclists should go out
and practice it is an empty car park rather than try to learn it when
you are in an emergency though.

http://www.sheldonbrown.com/brakturn.html

Tony

In message , at 09:32:56
on Tue, 17 Aug 2010, chris French
remarked:

It would be
quicker to dispense with the brakes and just go Flintstone style.

As I have just posted, the 34% figure is due to loss of control, and
is accurate for many (or even most) cyclists. You aren't going to
reduce that, HOWEVER efficient your brakes are. It may be as high as
50% if you ride in a deep crouch with your knees around your ears,
and is higher for a recumbent, or with heavy weights in rear panniers,
of course.

To what extent are cyclists with a child on a seat, or in a trailer
behind, inhibited from doing an "emergency stop" because of the effect
it might have in unseating their passenger?


IME, it doesn't make a lot of difference, if anything, a child in a
rear mounted seat improves matters as you have more weight where you
want it over the rear wheel. Yes, it is high up, but it's also further
back, which makes a big difference. Even just moving your weight back
by slipping off the back of the saddle helps.

I wasn't really asking about the physics - more the psychology.

But presumably the physics of a child sat between the saddle and the
handlebars is worse than if they weren't there?

I won't even mention those cyclists with a bag of shopping hanging
from each side of the handlebars.

They always have the possibility of extra emergency braking from the
bags and the front wheels.

I'd have though that from the Physics point of view it would make them a
lot more unstable and even more prone to an "over the handlebars"
moment. But I was asking mainly about whether the rider would be
inhibited from very sudden braking for fear of dumping the shopping on
the road - and it's not going to make steering any easier (as I found
out in Cambridge when a cyclist like that ploughed straight past me when
I was halfway across a pedestrian crossing, with a cry that meant "sorry
I'm out of control, save yourself while you still have time")
--
Roland Perry