Stopping Distances

laissez-faire · 19 Nov 2006 at 16:37

I knew the stopping distances were out of date, but reading the IAM magazine (a fairly reliable source I would say) the Highway Code stopping distances are the same today as they were in 1946!!!!!

That is just crazy. Also, if the Police are so obsessed with 'increased stopping distances from speeding' surely a modern car with ABS, disc brakes, good tyres etc is going to stop a lot quicker from 85mph than a lorry doing 53mph?

Trifid · 19 Nov 2006 at 16:42

But the thinking time hasn't changed since 1943.

Scania · 19 Nov 2006 at 16:45

laissez-faire said:
surely a modern car with ABS, disc brakes, good tyres etc is going to stop a lot quicker from 85mph than a lorry doing 53mph?

Depends if the lorry is empty, I've had a fair few cars "up my rear end" when I've braked hard whilst empty.

Trouble is, you never really know when a truck has weight on or not. :eek:

OllyM · 19 Nov 2006 at 16:47

R124/LA420 said:
Depends if the lorry is empty, I've had a fair few cars "up my rear end" when I've braked hard whilst empty.

Off topic a bit, but something I've always wondered... how quick is a lorry with nothing in the back?

No-One · 19 Nov 2006 at 16:47

In one of Clarksons videos he had a Ford Anglia, Ford Focus and a Range rover driving side by side at 60. When they get to a marked point they all performed an emergency stop. The anglia went over the distance that the highway code said it should take to stop. The Focus and Range Rover stopped in about half the distance in the highway code.

joseph_1_2 · 19 Nov 2006 at 16:51

also i believe on top gear they tested the maclaren f1's sucsessor (cant remember its name), and it did 120mph and stopped in half the distance for going at 60mph.

basically it stopped in half the distance while travelling at double the speed

laissez-faire · 19 Nov 2006 at 16:53

joseph_1_2 said:
also i believe on top gear they tested the maclaren f1's sucsessor (cant remember its name), and it did 120mph and stopped in half the distance for going at 60mph.

basically it stopped in half the distance while travelling at double the speed

The SLR - It was the same distance at double the speed which would require four times the braking power.

Scania · 19 Nov 2006 at 16:55

OllyM said:
Off topic a bit, but something I've always wondered... how quick is a lorry with nothing in the back?

Once upon a time, I had my Scania "off the clock" - Trucks are normally limited to 56MPH, on this occasion, I simply let the truck run away from me on a long downhill section of the M5 near Bristol.

I was'nt crazy enough to try to photograph my speedo whilst overspeeding!

75+ MPH may seem slow in a car, its bloody fast when you weigh upto 44 times the weight of the car! :eek:

Mr Jack · 19 Nov 2006 at 16:59

joseph_1_2 said:
basically it stopped in half the distance while travelling at double the speed

So its brakes were eight times better than the baseline car? I can believe that.

dirtydog · 19 Nov 2006 at 17:03

Mr Jack said:
So its brakes were eight times better than the baseline car? I can believe that.

And/or its tyres, which are what actually stops the car.

Slime101 · 19 Nov 2006 at 17:22

dirtydog said:
And/or its tyres, which are what actually stops the car.

Er, well....no. You could put great modern tyres on a car with crap brakes but itll still be crap.

But yes, for good brakes which do the stopping, you need good tyres to enable the car to remain grip.

laissez-faire · 19 Nov 2006 at 17:46

R124/LA420 said:
Once upon a time, I had my Scania "off the clock" - Trucks are normally limited to 56MPH, on this occasion, I simply let the truck run away from me on a long downhill section of the M5 near Bristol.

I was'nt crazy enough to try to photograph my speedo whilst overspeeding!

75+ MPH may seem slow in a car, its bloody fast when you weigh upto 44 times the weight of the car!

I must be missing something because to my eyes that speedo is reading 49mph?

Scania · 19 Nov 2006 at 17:48

laissez-faire said:
I must be missing something because to my eyes that speedo is reading 49mph?

Yes mate, it is, my point being I've had the same speedo off the clock - which if you look is 75MPH.

As I say, I was'nt crazy enough to try a picture @ that speed! :eek:

PeterNem · 19 Nov 2006 at 17:49

laissez-faire said:
I must be missing something because to my eyes that speedo is reading 49mph?

He was making a point that the clock only goes up to 70 (photo to show this). In the past he had it off the clock, but says he wasn't crazy enough to photo it, hence no photo!

dirtydog · 19 Nov 2006 at 17:51

Slime101 said:
Er, well....no. You could put great modern tyres on a car with crap brakes but itll still be crap.

But yes, for good brakes which do the stopping, you need good tyres to enable the car to remain grip.

Er well yes. The tyres are what stop the car ultimately. For example if a car has brakes powerful enough to lock up the wheels, then putting far more powerful brakes on it will not shorten the stopping distance one inch.

Dolph · 19 Nov 2006 at 17:54

The problem with quoted stopping distances is that, whether old or new, they are pretty much meaningless. Real world distance depends on far, far too many variables to make them useful, and to compound the problem most people can't judge distances in metres or feet when driving that well, so trying to memorise the distances is also a waste of time.

Better driver education would work much better.