One hundred MPH to zero.

[BliarOut]

What is the highway code figure?

A 996 Turbo just did this (datalogged) in 95M on Sky One's Zoom Zoom. A Caterham with no ABS only took 110M... Now, does this stimulate the old speed limits are out of date debate?

[J1mmyD]

There isn't a Highway Code figure for the simple reason that those speeds are illegal on public roads.

Using this www.nln.ac.uk/materials/downloads/rtf/Assignments_stopping_speeds.rtf the stopping distance should be 710 feet, or 216.41m sounds a bit on the high side, but probably correct for the HC figures

>> Edited by J1mmyD on Tuesday 18th April 20:41

[r5gttgaz]

96 metres @ 70mph.

[SamHH]

The Highway Code typical stopping distances only go upto 70mph: 75 metres. Looking at Autocar's road test data most cars stop from 70 in about 50 metres

[SamHH]

r5gttgaz said:

96 metres @ 70mph.

That's including thinking distance.

[madbadger]

I don't think the highway code recommends that you travel at 100mph.

It says that from 70 you will take 315ft or 96m.

Can 911s co 100mph on motorways, then?

[BliarOut]

madbadger said:

I don't think the highway code recommends that you travel at 100mph. It says that from 70 you will take 315ft or 96m. Can 911s co 100mph on motorways, then?

Easily

[madbadger]

Extrapolating the Highway code figures I make 100mph = 600feet, 180m.

/

[J1mmyD]

OK ... now that everyone's quoting figures way below the one I just worked out, you people have got me wondering .... according to the figures I've just found, thinking time alone takes you 33m.

Braking distance is a function of the sqaure of the total speed .... gonna work this out 'on paper':

thinking distance (feet):

1.1 * 100 = 110

braking distance (feet):

0.06 * 100 * 100 = 600

stopping distance (feet):

110 + 600 = 710

710 feet = 8520 inches = 216.408m

Am I wrong, or is the equation I've just got wrong?

[vonhosen]

The simple formula to use (roughly what the highway code does) for working out the distance in feet is

Divide the speed by ten & multiply the original speed by that. Half the result to get your braking distance in feet.

ie

100mph/10) = 10
10 x 100mph = 1000
1000/2 = 500 feet.

Thinking distance at about .7 sec = roughly 1ft per mph.

Therefore braking distance at 100mph = 500 feet.
Stopping distance at 100mph = 600 feet.

[turbobloke]

vonhosen said:

Thinking distance at about .7 sec = roughly 1ft per mph. Therefore braking distance at 100mph = 500 feet. Stopping distance at 100mph = 600 feet.

Except that a 911 turbo will stop in 400 feet, so 600 has an error margin of 50%. While the average car won't stop like a 911 Turbo, though a small number will outstop one, this reinforces the rightful genre of the (revised) Huighway Code as 'fantasy'.

[madbadger]

I went:
distance thinking in feet = speed in Mph and d Braking increases by x0.5 per 10 mph so:

V = d Th + d Br

20 = 20 + 20 x 1 = 40
30 = 30 + 30 x 1.5 = 75
40 = 40 + 40 x 2 = 120
50 = 50 + 50 x 2.5 = 175
60 = 60 + 60 x 3 = 240
70 = 70 + 70 x 3.5 = 315
80 = 80 + 80 x 4 = 400
90 = 90 + 90 x 4.5 = 495
100 = 100 + 100 x 5 = 600

[vonhosen]

turbobloke said:

vonhosen said: Thinking distance at about .7 sec = roughly 1ft per mph. Therefore braking distance at 100mph = 500 feet. Stopping distance at 100mph = 600 feet. Except that a 911 turbo will stop in 400 feet, so 600 has an error margin of 50%. While the average car won't stop like a 911 Turbo, though a small number will outstop one, this reinforces the rightful genre of the (revised) Huighway Code as 'fantasy'.

I haven't suggested that the advice in the highway code is anything but basic cautionary advice.
The stopping distance of a vehicle is not going to be the same for each vehicle or in all conditions. I have merely provided a way for you to work out what the highway code would show for speeds differing from those in print.

[BliarOut]

The physics part

1MPH = .44 M/S

*100 MPH = 44M/s

Therefore thinking distance in .7 s = 30.8M

+ 95M Actual stopping distance from 100 MPH

=125.8M total stopping distance.

[GreenV8S]

100 mph to zero in five seconds represents an average decelleration of about 1G, which is a reasonable target to aim for under good conditions. You'll travel about 125 meters while you do it.

On good standard road tyres you might get up to 1.15 G under ideal conditions, which brings your braking time down to about 4.4 seconds and you braking distance down to about 110 meters.

To get below that you need unusually sticky tyres, or a significant amount of aerodynamic downforce.

[turbobloke]

vonhosen said:

I haven't suggested that the advice in the highway code is anything but basic cautionary advice.

Accepted, but I'm definitely suggesting important parts of it are archaic and inaccurate and are retained in that form purely as a means of bolstering myths about speed and safety that belong to another era, one that is now consigned to history. We should not be indoctrinating people with lies inspired by safety totalitarianism, the truth will do nicely and Highqay Code stopping distances do not represent the situation today and are basically lies in print. When lies in print are sanctioned by the state, they acquire a name, and the state acquires a corresponding reputation.

[turbobloke]

GreenV8S said:

100 mph to zero in five seconds represents an average decelleration of about 1G, which is a reasonable target to aim for under good conditions. You'll travel about 125 meters while you do it. On good standard road tyres you might get up to 1.15 G under ideal conditions, which brings your braking time down to about 4.4 seconds and you braking distance down to about 110 meters. To get below that you need unusually sticky tyres, or a significant amount of aerodynamic downforce.

Or a 911 Turbo

[r5gttgaz]

smeggy said:

HC maths uses: 0.67 secs thinking time, -0.67G deceleration From 100mph applying the maths: thinking distance = 30m, braking distance (d=VV/2a) = 152m Total baking distance is 182m = 597 ft Note, the HC is way out of date, modern cars can brake much harder.

Is that how long it takes a Victoria sponge to stop, 597ft?

[smeggy]

HC maths uses: 0.67 secs thinking time, -0.67G deceleration

From 100mph applying the maths:
thinking distance = 30m, braking distance (d=VV/2a) = 152m
Total braking distance is 182m = 597 ft

Note, the HC is way out of date, modern cars can brake much harder.

[BliarOut]

smeggy said:

HC maths uses: 0.67 secs thinking time, -0.67G deceleration From 100mph applying the maths: thinking distance = 30m, braking distance (d=VV/2a) = 152m Total braking distance is 182m = 597 ft Note, the HC is way out of date, modern cars can brake much harder.

Shows how out of date it is... The Porsche only took 95M actual braking