With reference to recent Back Room polls on the priorities of BRs when buying a new car, I asked my wife what her priorities were. One of the top things on her list was "good brakes" - which seems pretty reasonable to me.
But how does one find out which models have good brakes? We've got NCAP scores to tell us which cars come out best when we can't stop, but I'd rather know which car did best at stopping. Car mags have plenty of tables that give us 0-60 figures, but not 60-0 figures.
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What is good, or how good is good. Power brakes on BX, Xantia and other hydro-pneumatic suspended Cits are IMHO the best, max stop for min pedal push. Others report them as over powered. Worst I've ever driven were on a Mk1 Polo; sponges would have been better, never had the courage to press the pedal really hard in case i broke something.
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Why not strap a set of AP Racing 6-pots onto your current car.
:-)
I'd have thought that any car* with ABS and decent tyres would be able to stop suitably quickly.
* = not SUV type vehicles.
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A lot of people especially women perceive good brakes as ones with a very light pedal. This is fine with ABS but means check braking needs more thought as otherwise you'll stand it on its nose when you just meant to slow a little. Hence the lines of brake lights on motorways when someone dabs the brake pedal.
Better brakes are those with good pedal feel and probably the best was the Subaru Estate I had which were fantastic. The worst apart from any fully powered citroen system which are pointless, was a Nissan Almera which are over servoed & very unprogressive.
Jim
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>The worst apart from any fully powered citroen system which are pointless
The fully powered Cit system gives phenomenal braking performance though; so good in fact that it takes some time to get used to after ordinary cars, but when you do it is hugely reassuring. Combined with abs in the BX it was truly wonderful. One big advantage of the old Citroen system was that it allowed variable brake distribution between front and rear brakes depending on load--more braking to the rear wheels if you have passengers on board. This was available on all hydropneumatic models as far back as the 1950s. Of course now we have electronics to do all this for us, and with more subtlety too, but Citroen's system was clever, simple, and very reliable.
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i drove a new megane the other day and the brakes were very good. the stopping distance is one of the best - even beating cars costing much more.
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Car mags have plenty oftables that give us 0-60 figures, but not 60-0 figures.
Interesting - motorcycle magazines always used to give 30-0 & 60-0 figures - which made a mockery of the Highway Code figures!
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Autocar road test results (the bit at the back of the mag)give 60-0 figures.
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Brakes are usually capable of locking the wheels. This is virtually always true for front wheels, but the rear brake pressures are limited by valves to prevent the equivalent of a high speed application of the handbrake!
If you make the assumption that all ABS systems are approximately comparable, then I would expect to see cars that have;
a) a good static weight distribution
b) a low centre of gravity
c) a long wheelbase
d) big sticky tyres*
coming out with the best stopping times / distances. My logic for points a, b, and c is that these points allow the rear brakes to contribute more, instead of the majority of the work to be done by the front tyre's contact patch. In an extreme case, the rear brakes on an original Mini are really only there for the handbrake function, their effect during footbrake application is negligible.
* for rubber, which conforms to the road surface, the usual arguments about friction being independent of area do not apply.
number_cruncher
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Thanks for that - but what exactly do you mean by "big sticky tyres"?
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I mean that tyres which have a larger contact footprint will be able to generate more force than a similar tyre with a smaller footprint.
By sticky, I mean that a tyre with a compound optimised for grip rather than longevity will again be capable of generating more force.
number_cruncher
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Whilst searching Google I came across the following, which was written in March 1998 by the Slower Speeds Initiative, PO Box 746, Norwich NR2 7LT.
"What the European Union should do
Ensure (through construction and use regulations) that new vehicles manufactured for use in Europe have a top speed of no more than 120 kph and are fitted with variable speed limiters."
They won't get my support ~ 120 kph = 75 mph!
--
L\'escargot by name, but not by nature.
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A quick scan of the only AutoCar I have to hand (1999), reveals the car with the best brakes is a Ferrari 360 Modena F1 with a 60-0mph time of 2.4 seconds.
Tyro, is that the sort of car your wife has in mind :)
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Any new car will have good brakes. Some cars may have better braking than others, but they will all be good. They all have to conform to a minimum standard.
--
L\'escargot by name, but not by nature.
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My wife, I am glad to report, is very financially prudent, and even if the household budget did stretch that far, she would feel that it was not money well spent.
She would probably also fear that I might make rather more use of the acceleration than I ought to, and even the knowledge that the brakes were good would not alleviate her anxiety much.
Of course, if there was one going cheap on ebay, I might just have a go at persuading her that the brakes were very, very, good.
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The Laguna2 has excelent brakes. They stop like nothing on earth (fat sticky tyres as well)
HOWEVER
They take some getting used to. Stamp on these things in panic and the system takes over. No wheels lock, front or back, no feedback because the brake assist has taken over, just pure stopping power. Does not feel that way tho! Most disconcerting until you get reassured by the system.
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Having driven the new Megane, I would say they've got the best stopping power. Just touching them unawares can bring the car to a screeching halt.
However, for an emergency stop, they're fantastic. I tried them on an open road doing an emergency stop from 60MPH, and my eyeballs were hanging out on stalks afterwards.
Car perfectly controlled, no screech, no smoke, just a gentle vibration through the brake pedal. However, slightly disconcerting is that the Emergency Brake Assist causes the brake pedal to sink even further under your foot as the computer increases the brake pressure.
Wouldn't want to be behind one of them when it has to stop in a hurry.
Incidentally, in an emergency stop on the motorway, where one is heading in a straight line, in a car with no ABS, is it best to just push the pedal as hard as possible, or try to gauge the point where the wheels lock?
Personal opinion is to try to come to a halt with all four wheels smoking, but some disagree and say that maintaining control of the car is more important.
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As it happens, last week I thought I'd try out the electronic brake assist on my V70. Unbelievable!
Nobody else around.
Perfect visibility.
Held speed at exactly an indicated 60MPH.
Picked the relative position of a roadside tree as an imaginary obstacle in the road.
Left it as late as I dared.
Went quickly from throttle to brake pedal.
The car simply stood on its nose and stopped.
No squirming, no tramlining, no noise, no drama.
Where was the tree?
Still some distance in front.
I have never relied on ABS in my driving life - in fact apart from such tests I have only ever had it kick in at walking speed on ice - let alone the extra benefit of brake assist, but this was a seriously impressive display.
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"However, slightly disconcerting is that the Emergency Brake Assist causes the brake pedal to sink even further under your foot as the computer increases the brake pressure."
Yup thats the feeling, all feedback goes from the foot when the EBA really gives it some welly. And while you are still standing on the brake after the stop the pedal sinks even further.
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That's one of the little tests that Ford demonstrate to us to show how good the Mondeo is, they run it alongside a Ferrari on a test track and then simultaneously slam on the brakes, the Mondeo stopped much quicker than the Ferrari, I have no idea what model Ferrari that was against though, obviously not a great one! :-)
Blue
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German car mags measure the braking distance of the cars they test. Generally they measure the distance required to decelerate from 100km/h to 0 with cold brakes and warm brakes and with the car laden and unladen. Average seems to be around 40m, extended when the car is laden or the brakes are hot. Worst seem to be small, cheap hatchbacks and large SUVs, both around 43m ish. Best I've seen was the Porsche Carrera and BMW M3, both 34m, I own an M3 and the braking force is unbelievable. Note that at 200km/h the braking distance extends to 146m.
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Actually, best I've ever seen was that Mercedes-McClaren on Top Gear where Clarkson threw out the anchors at 120MPH and came to a halt within the stopping distance for 60MPH.
I want a car whose brake disks can be made to glow.... ;-)
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abs and brakes:
am i right in the impression that some of the above posts are suggesting that abs means shorter braking distances?
or is it true that in general abs does not equate to shorter braking distance?
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abs stops the wheels/tyres from skidding, thus improving brake stop distance.
when tyres skid on the floor, they are not slowing as much as a tyre that is just slowing to its maximum with out skidding.?
did that make sense?
ie: the tyre skidding is just sliding along the floor, losing traction
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ABS will only give a shorter shopping distance compared to a car which has locked all four wheels and is sliding along merrily without slowing down. Theoretically the maximum braking force is just before the tyres lose grip, so activating the ABS means you are braking too heavily. The advantage is that amateur drivers like ourselves can just stand on the middle pedal in an emergency and know that the brakes are coming on (and off!) to their maximum ability. Also, people forget that ABS allows you to steer around the obstacle rather than hope to stop in time.
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Dont forget a lot of the posts mention "brake assist" and "electronic brake distribution"
Brake assist automatically places pressures on the brake system you as an ordinary driver might not.
EBD ensures that maximum pressures are going to all the wheels as required.
and ABS is the juggler making sure all this emergency pressure is not locking up the wheels.
Add this lot up and you have the maximum available braking effect at each wheel that is dynamically required to stop the car in the shortest distance possible.
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RF is quite right to mention these electronic aids.
As ever, there is a bit of grey between the black and white. Tyres produce their maximum traction or braking forces at about 20% slip, and indeed need to slip to an extent to produce any significant force at all.
To obtain the minimum braking distance, all the wheels would operating at this slip level for maximum force. Current technology, where in particular the *exact* speed of the car is not measured by any on-board computer, cannot acheive exactly this optimum slip, so, the ABS cycles around this optimum, which is why ABS tends to pulse in extreme situations.
However, the prime aim of ABS is to ensure that wheels do not lock fully, when all steering and directional control would be lost.
number_cruncher
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abs and brakes: am i right in the impression that some of the above posts are suggesting that abs means shorter braking distances? or is it true that in general abs does not equate to shorter braking distance?
Oh No!!! Groundhog day yet again!!!
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Thanks to all for your thoughts
Thanks esp for Paul to alerting me to Autocar's Test Results section. I'd never really read it, so I went out and bought a copy. Quite an interesting and useful section. However, I had a couple of reservations about it.
1) It's not really comprehensive - good on the big sellers, and on prestige and performance cars (it has considerably more tests for BMWs than for Renaults), but does not include, for example Renault Kangoo, Citroen Berlingo, Rover 25, Mazda 2, Mazda 3, and (surprisingly) the Honda CR-V.
2) There are odd discrepancies. Is the Ford Fiesta 1.25 really so much better at stopping than the 1.4? Is the BMW X5 4.4 so much better than the 3.0?
Other magazine's road test statistics also throw up odd discrepancies. In the Jan 2004 issue of What Car, the braking distances for the Gold were better than those of the Megane, but in the Nov 2004 issue of Test Drive, it was the other way around. It surely can't be because the first compared 1.6 petrol engines, and the second compared 1.9 diesels? How seriously can I take the test results and statistics in car magazines?
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As mentioned above, weight transfer towards the front under braking means that the rear wheels don't do much of the stopping. Mid or rear engined cars can use the rear brakes better so they can have better stopping power.
But I'm sure the Autocar tests answers above were more useful to what you actually wanted ;-)
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ive read that BMW have a new system on the 3 series coming out next year called Soft Stop....more from channel 4 motoring below....too many electronics!
Dynamic stability control (DSC) is standard on four-cylinder models, and a new upgraded DSC+ will be fitted in six-cylinder versions; this incorporates a Brake Standby facility to pre-tension the brakes when the driver lifts off the accelerator, Soft Stop to modulate brake application at low speeds, a Start-Off Assistant to prevent roll-back when hill starting and a detector to ensure the brake discs are kept dry on wet roads. Active Steering, as fitted in the 5- and 6-Series, is optional in six-cylinder versions to give a speed-variable steering ratio and, in combination with the DSC, oversteer control and extra stability under braking on slippery surfaces
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Geez! how long will the pads ( and disks ) last with all that going on all the time!
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