Stopping Distances

[scoobman]

Can someone confirm what the stopping distances are for over 70mph in feet and meters(315ft - 96m)

If I remember rightly
80 is about 400ft
90 is about 495ft
100 is about 600ft
110 is about 715ft
120 is about 840ft

Can someone confirm that the above is correct - what are the distances in meters?

Thanks peeps
Scoobman

[vonhosen]

scoobman said:

Can someone confirm what the stopping distances are for over 70mph in feet and meters(315ft - 96m)

If I remember rightly
80 is about 400ft
90 is about 495ft
100 is about 600ft
110 is about 715ft
120 is about 840ft

Can someone confirm that the above is correct - what are the distances in meters?

Thanks peeps
Scoobman

They are correct.

80 = 122m
90 = 151m
100 = 183m
110 = 218m
120 = 256m

Edited by vonhosen on Friday 11th May 21:57

[scoobman]

Thanks

[BliarOut]

Porsche 996 with PCCB

From 80 MPH

Thinking distance = 80 feet
Braking distance = 182 feet
Total = 262 feet or 79.8576 metres.


Porsche 996 without PCCB

From 120 MPH

Thinking distance = 120 feet
Braking distance = 482.49 feet
Total = 602.49 feet or 183 metres

Shows how outdated the Highway Code figures are...

Edited by BliarOut on Friday 11th May 22:20

[scoobman]

Anyone got the distances in meters?

Whats PCCB? - As there is a massive difference in the stopping distances with and without.
I didnt think that big flash brakes made that much difference to stopping distances.
As - ok you have a larger contact patch between the pad and the disk so more energy can be tranfered into heat and also groves to take the gas away. But most of this is for advantages in prolonged heavy use to keep the temps down.
But at the end of the day you still have all the weight going forward and the point where brakes lock is still going to be about the same and it is still going to take you many feet to stop at a big speed. So is PCCB defying the laws of physics.

Cheers
Steve

[vonhosen]

scoobman said:

Anyone got the distances in meters?

Whats PCCB? - As there is a massive difference in the stopping distances with and without.
I didnt think that big flash brakes made that much difference to stopping distances.
As - ok you have a larger contact patch between the pad and the disk so more energy can be tranfered into heat and also groves to take the gas away. But most of this is for advantages in prolonged heavy use to keep the temps down.
But at the end of the day you still have all the weight going forward and the point where brakes lock is still going to be about the same and it is still going to take you many feet to stop at a big speed. So is PCCB defying the laws of physics.

Cheers
Steve

I've put meters on my post.

PCCB = Porsche Ceramic Composite Brakes.

[BliarOut]

Porsche's ceramic brakes. I couldn't find two similar test results so the PCCB car is doing 80 MPH and the standard car is going 40 MPH faster.


To compare eggs with eggs at 80 MPH the Porsche can stop in 40 metres less....

Edited by BliarOut on Friday 11th May 22:33

[scoobman]

vonhosen said:

scoobman said:

Anyone got the distances in meters?

Whats PCCB? - As there is a massive difference in the stopping distances with and without.
I didnt think that big flash brakes made that much difference to stopping distances.
As - ok you have a larger contact patch between the pad and the disk so more energy can be tranfered into heat and also groves to take the gas away. But most of this is for advantages in prolonged heavy use to keep the temps down.
But at the end of the day you still have all the weight going forward and the point where brakes lock is still going to be about the same and it is still going to take you many feet to stop at a big speed. So is PCCB defying the laws of physics.

Cheers
Steve

I've put meters on my post.

PCCB = Porsche Ceramic Composite Brakes.

That you have. I am tired and being a f_ckwit. Appologies

[standards]

Fantastic technology.

What about the car, lorry, caravan behind you?

Mind you I'm jealous of course-Porsche of any description is beyond my means!

[BliarOut]

standards said:

Fantastic technology.

What about the car, lorry, caravan behind you?

Mind you I'm jealous of course-Porsche of any description is beyond my means!

In a Porsche what's behind is just as important as what's in front if you want to throw out the anchors. You have to adjust your driving if you ever get a muppet tailgating you. What they fail to realise is that the stopping on high performance cars is even more impressive than the acceleration

[GreenV8S]

Knowing the distance in feet or meters is not very useful in practice imo unless you are very good at estimating long distances by eye - something that I doubt is a common skill.

Far more useful to know how many seconds it will take you to drive that distance at your initial speed, effectively how long the gap is that would enable you to stop if the car in front magically turned into a brick wall. And that's actually a lot easier to estimate by mental arithmetic too. For braking at 1G it is roughly speed (in mph) divided by 40, plus one second for reaction time. So at 80 mph in the dry if you count off three seconds, that's the earliest point you could realistically have hoped to come to a halt if you'd done a 1G emergency stop at the point you started counting. The result is a time, but it's not how much time it would take you to stop, it's how long it would take you *at your initial speed* to cover your stopping distance.

At 0.5G the braking time roughly doubles, the reaction time doesn't, so the 'stopping time' at 80 mph would be five seconds.

At 0.1G the braking time goes up by a factor of ten. If it's icy and you somehow got up to 80 mph, the 'stopping time' would be around 21 seconds. (That's an *awfully* long way at 80 mph.)

If you can estimate how much grip there is as a proportion of the normal dry grip, the rest is very easy to do in your head for any speed.

[Vaux]

scoobman said:

Thanks

You can work it out for any speed.
Stopping distance= braking distance + thinking distance

Thinking distance = speed in feet (60 mph = 60 feet)
Braking distance = speed squared/20 (60mph = (60*60)/20 = 180)

Therefore stopping distance = 60 plus 180 = 240 feet

150mph = 150 plus (150*150)/20 = 1275 ft = 425 yds = 388.62 Metres.

[R_U_LOCAL]

Vaux said:

scoobman said:

Thanks

You can work it out for any speed.
Stopping distance= braking distance + thinking distance

Thinking distance = speed in feet (60 mph = 60 feet)
Braking distance = speed squared/20 (60mph = (60*60)/20 = 180)

Therefore stopping distance = 60 plus 180 = 240 feet

150mph = 150 plus (150*150)/20 = 1275 ft = 425 yds = 388.62 Metres.

I'm a simple man and squaring numbers is a bit much for my feeble mathematical mind. (And not wanting to be pedantic, but your maths is a little out on the 150MPH calculation, Vaux )

I prefer the following multipliers, which will give you the braking distance in feet only (add the speed in MPH to give the overall stopping distance in feet).

20MPH X 1 = 20 feet braking distance
30MPH X 1.5 = 45 " " "
40MPH X 2 = 80 " " "
50MPH X 2.5 = 125 " " "
60MPH X 3 = 180 " " "
70MPH X 3.5 = 245 " " "
80MPH X 4 = 320 " " "
90MPH X 4.5 = 405 " " "
100MPH X 5 = 500 " " "
110MPH X 5.5 = 605 " " "
120MPH X 6 = 720 " " "
130MPH X 6.5 = 845 " " "
140MPH X 7 = 980 " " "
150MPH X 7.5 = 1125 " " "

Another interesting fact with braking distances, which applies irrespective of how efficient your brakes are, is that if you double your speed, you quadruple your braking distance.

[willibetz]

R_U_LOCAL said:

Vaux said:

scoobman said:

Thanks

You can work it out for any speed.
Stopping distance= braking distance + thinking distance

Thinking distance = speed in feet (60 mph = 60 feet)
Braking distance = speed squared/20 (60mph = (60*60)/20 = 180)

Therefore stopping distance = 60 plus 180 = 240 feet

150mph = 150 plus (150*150)/20 = 1275 ft = 425 yds = 388.62 Metres.

I'm a simple man and squaring numbers is a bit much for my feeble mathematical mind. (And not wanting to be pedantic, but your maths is a little out on the 150MPH calculation, Vaux )

I prefer the following multipliers, which will give you the braking distance in feet only (add the speed in MPH to give the overall stopping distance in feet).

20MPH X 1 = 20 feet braking distance
30MPH X 1.5 = 45 " " "
40MPH X 2 = 80 " " "
50MPH X 2.5 = 125 " " "
60MPH X 3 = 180 " " "
70MPH X 3.5 = 245 " " "
80MPH X 4 = 320 " " "
90MPH X 4.5 = 405 " " "
100MPH X 5 = 500 " " "
110MPH X 5.5 = 605 " " "
120MPH X 6 = 720 " " "
130MPH X 6.5 = 845 " " "
140MPH X 7 = 980 " " "
150MPH X 7.5 = 1125 " " "

Another interesting fact with braking distances, which applies irrespective of how efficient your brakes are, is that if you double your speed, you quadruple your braking distance.

Being even more simple, I find multipliers a bit tough to remember. But basic maths hasn't changed much. For the example given:

(60 x 60)/20 which is a bit daunting to work out in your head

is equivalent to

60 x (60/20) which is easy.

Incidentally, I wonder how many cars were capable of 150mph when stopping distances were first estimated?

And can we presume, when the eagerly anticipated revision to the Highway Code is likely to deny accidents and alienate cyclists, that somebody will also have updated the section on stopping distances?

WilliBetz

[Vaux]

R_U_LOCAL said:

(And not wanting to be pedantic, but your maths is a little out on the 150MPH calculation, Vaux )

? 1125 is the calculated braking distance, but I was giving stopping distance, so added on the other 150.

Edited by Vaux on Saturday 12th May 22:02

[R_U_LOCAL]

Vaux said:

R_U_LOCAL said:

(And not wanting to be pedantic, but your maths is a little out on the 150MPH calculation, Vaux )

? 1125 is the calculated braking distance, but I was giving stopping distance, so added on the other 150.

Edited by Vaux on Saturday 12th May 22:02

*Re-reads*

*Is thick*

Again.

[Vaux]

R_U_LOCAL said:

*Re-reads*

*Is thick*

Again.

Join the club......