Speed limits - people who ignore them

mcpitman

gilbert_and_sullivan wrote: »

I'd be interested to see how a light vehicle with massive brakes for its weight can stop any quicker than a lesser vehicle, equipped with ABS on the point of lock up, but without locking, on all 4 wheels.
Though it might feel faster braking, if the wheels are locking it won't be.
Are there different physics at work here.

My now quite old Merc coupe is the fastest braking car i've ever owned, it has large (but not blinged/labelled/red/yellow look at meeee) 4 pot front calipers, and 2 pot opposed rear calipers, it has a working well ABS but too old to have electronic brake force distribution, however for its type it is very light compared to the lardy modern cars that replace it.

Now i can brake from almost any speed on the point of lock up in any conditions, but without locking up due to the ABS.

Other more advanced systems will be able to stop faster i have no doubt due to better/faster electronics on the brakes and suspension..

Please explain how a car without ABS and firm suspension can stop faster, lighter pedal effort yes maybe we've all driven overservoed cars and boy are they horrid things, often so called warm hatches,

But there are only and ever will only be 4 footprints of rubber on the road, the choice of rubber will and does make a huge difference as anyone with an ounce of common sense knows, but how pray given similar levels of grip can one car at the point of lock stop any qucker than another, assuming the contact surface areas of the tyres in ratio to overall weight is similar and tyre quality the same?

I don't want an argument, and i don't need anyone telling me i haven't driven a real car so wouldn't know, pub bore comments unwelcome, this is a genuine question.

I think you are going into the world of friction co-effecients etc.

Simple theory, F1 car vs Road Car.

F1 car has 4x tyres and brakes, so does a Road car. Although the compounds and materials used will vary from car to car and spec to spec.

No ABS on F1 cars, but it'll stop quicker than a road car.

Strider590

gilbert_and_sullivan wrote: »

I'd be interested to see how a light vehicle with massive brakes for its weight can stop any quicker than a lesser vehicle, equipped with ABS on the point of lock up, but without locking, on all 4 wheels.
Though it might feel faster braking, if the wheels are locking it won't be.
Are there different physics at work here.

My now quite old Merc coupe is the fastest braking car i've ever owned, it has large (but not blinged/labelled/red/yellow look at meeee) 4 pot front calipers, and 2 pot opposed rear calipers, it has a working well ABS but too old to have electronic brake force distribution, however for its type it is very light compared to the lardy modern cars that replace it.

Now i can brake from almost any speed on the point of lock up in any conditions, but without locking up due to the ABS.

Other more advanced systems will be able to stop faster i have no doubt due to better/faster electronics on the brakes and suspension..

Please explain how a car without ABS and firm suspension can stop faster, lighter pedal effort yes maybe we've all driven overservoed cars and boy are they horrid things, often so called warm hatches,

But there are only and ever will only be 4 footprints of rubber on the road, the choice of rubber will and does make a huge difference as anyone with an ounce of common sense knows, but how pray given similar levels of grip can one car at the point of lock stop any qucker than another, assuming the contact surface areas of the tyres in ratio to overall weight is similar and tyre quality the same?

I don't want an argument, and i don't need anyone telling me i haven't driven a real car so wouldn't know, pub bore comments unwelcome, this is a genuine question.

Because the discs are cross-drilled/vented, they don't fade, it has big twin pot callipers, the pads are a special sprint/track compound and the tyre's are so soft that driving on a freshly "dressed" road means you'll be spending half an hour pulling stones out of the tyre thread with a pair of long nose pliers.

It will lock a wheel if you go over a bump or minor pothole in the road whilst braking, because for a fraction of a second that corner of the car has less contact with the ground and when you consider the weight, that doesn't leave much down force on that wheel. Oh and no it's not easier, it's actually harder because the brakes have no vacuum assist unit on the master cylinder.

Car_54

rich13348 wrote: »

I was of the opinion that you should not pull out on to another road if it was going to force a driver on that road to alter their speed or trajectory.

That's not an opinion, that's the law!

"... no vehicle shall proceed past such one of those lines as is nearer the major road into that road in a manner or at a time likely to endanger the driver of or any passenger in a vehicle on the major road or to cause the driver of such a vehicle to change its speed or course in order to avoid an accident."

The Traffic Signs Regulations and General Directions 2002, section 25(2).

Mr_Mink

mcpitman wrote: »

I think you are going into the world of friction co-effecients etc.

Simple theory, F1 car vs Road Car.

F1 car has 4x tyres and brakes, so does a Road car. Although the compounds and materials used will vary from car to car and spec to spec.

No ABS on F1 cars, but it'll stop quicker than a road car.

To further that. Weight and momentum would play a large part in the stopping distance.

Coupled with reaction times, I'd say it's entirely probable that a kit car would stop faster than pretty much anything bar another similarly focused car.

Cornucopia

bazster wrote: »

There is a lot wrong with driving significantly below the speed limit in good conditions. As orlao points out, do it in your driving test and you will fail. It used to be called "failing to make good progress", but I don't know if that's still the terminology examiners use.

Not really. Examiners like to see people "make progress" in their tests because it demonstrates confidence and a good awareness of limits and hazards. But it shouldn't be taken as official sanction to hare around for the rest of one's driving career at the limit or above it. Once you are paying for your own car, fuel and brake pads you may wish to determine a driving style that is more suitable.

Those who drive at 45 mph in a 60 mph zone are almost invariably ignoring the speed limit and everything else. As described by the OP, they demonstrate their ignorance of the speed limit by blithely continuing at 45 mph when they reach a 30 mph zone. They are stupid, inconsiderate and dangerous drivers.

Possibly, but single-carriageway roads (even those with NSL) are very variable. There are some that are dead straight for miles, and others that are like roller-coasters. It is necessary to adjust your driving style to the situation (and not over-generalise about X mph being bad, slow or inconsiderate).

angela110660 wrote: »

Ha ha. Made me smile as I remember my old driving instructor John flashing the brake lights at impatient drivers when I was learning to drive in the 70s. And yes, it makes you feel smug when you catch up at the lights or roundabout.

This can be classic confirmation bias - you only catch up with a proportion of them, but never see the ones that get away before the lights change, or the roundabout is blocked.

Retrogamer

mcpitman wrote: »

Can you, or have you ever driven a car on a real road?

You drivel based comments, seem antagonistic at best, and from nearly every comment you have made you appear to be a 12 yr old forum troll.

Or is this a matter of darkness (again)?

I'm suspecting it's Spicey McHaggis

reeac

The drivers that interest me are those in the big courier vans who charge around our local twisty, narrow country roads but show tremendous respect for 30 limits. My theory is that they've notched up mucho points on their licences and are worried about disqualification.

jase1

I love the way that people who defend 40mph drivers on forums never, ever address the core point that many of them continue at 40mph through the villages.

Speeding in built up areas is reprehensible... yet these people can't even bring themselves to comment on it.

People who drive through built up areas, through 30mph limits at 45mph should have their licences taken away and not returned IMO. Those who drive at 45mph past schools should be operated upon, to ensure they can never reproduce.

dcouponzzzz

I stick to the road's limit or 10% above it (30-33, 40-44) everywhere but the motorway, where I idle along at 55 mph behind the lorries. I do often get lorries and others overtaking me, but considering they have 2 lanes in which to pass me I feel no remorse :rotfl:Eco-driving the MSE way!

WellKnownSid

jase1 wrote: »

Speeding in built up areas is reprehensible... yet these people can't even bring themselves to comment on it.

Sat in a hotel last year waiting for a colleague, I watched people gathering for their 'speed awareness' course which appeared to be run by a certain motoring organisation.

They were all chatting around the coffee dispenser - and it became clear that most had been caught speeding locally on a particular 30mph stretch - which no doubt was outside a hospital / school / kitten rescue centre.

Everyone was local, this stretch had been 30mph since the dawn of time, and they should have all known better - yet the talk was about being 'unlucky' and that 'everybody did that speed along there', or that 'modern cars were so much safer nowadays'. The funding of local policing was mentioned a few times too and the phrase 'should be out catching real criminals'.

Not one person could accept that they had failed to follow simple instructions...