Are brakes under powered on modern cars

[Globalti]

I can't remember the last time I had to do an emergency stop in my Passat - I seem to be able to anticipate most situations and avoid the need.

Our old Land Rover 90 was pretty scary - it was so short that if you hit the bakes, weight transfer would unload the back axle and the rear wheels would lock up. It had a pressure limiter on the rear brakes but that seemed to make no difference.

 

[Night Train]

In any car to car comparison you would need to take the tyres into account.

My Skoda's ability to stop sharpish is very dependent on the condition and age of the tyres. I have no fears of an emergency stop at high speed but only when the tyres are fairly new. I am hoping that the next tyre change will be a chance to change all four for something better.

What I find interesting is the ability of my trailer to pull up a bit sharper then the car wants to. On any rapid stop I can feel the trailer pulling the car to a stop very effectively.

My old S3 Land Rover stopped fine when on radial Michelin XCL tyres. On crossply Firestone SATS it would have stopped quicker had I put my foot out the door Flintstone style.

 

[fimm]

I emailed someone who develops after market brake setups & he gave me a lot of information.

The long & the short of it is that cars produced over the last 10 years have had brake systems which have progressively got less powerful for a given pad pressure, however the servo assistance has progressively increased the pad pressure to compensate (there are lots of reasons for this). As most people judge power but how sharp the initial bite of brakes is this works fine, however for people who compartmentalise braking performance & are used to brakes which operate at lower pad pressures they will be left feeling that the brakes are underpowered compared those brakes. The upshot of all this is that someone who is trained & is skilled will be able to stop the same car quicker with a 15 year old brake setup, but 'average joe' will stop quicker with a setup designed in the last 5 years.

Would you mind explaining this a bit more? I'm just curious. I don't drive much, and I find when I do get in a car (hire car, we don't own one) that I find the brakes really vicious to start with - my memory of my mother's car when I drove it regularly more than 10 years ago was that you had to press the pedal quite a way before the brake started to bite, while modern cars you hit the braking point much more quickly. Does that sound like a simple way of saying what you've just said?!

 

[Archie_tect]

Hate driving my M-in-L's 'S'reg Fiesta... the brakes are awful.

 

[Over The Hill]

I had a Polo once (not for long - horrid little car) but apparently VW had a problem when they made them right hand drive as the brake servo was in the way so they just left it off UK models.

You really had to push the brakes hard to get them to do anything. Then driving any other car you keep stopping dead until you get used to it.

 

[GrasB]

Would you mind explaining this a bit more? I'm just curious. I don't drive much, and I find when I do get in a car (hire car, we don't own one) that I find the brakes really vicious to start with - my memory of my mother's car when I drove it regularly more than 10 years ago was that you had to press the pedal quite a way before the brake started to bite, while modern cars you hit the braking point much more quickly. Does that sound like a simple way of saying what you've just said?!

What bit do you want expanded on? I'd break down the performance of brakes into 4 categories:

Bite deals with how the brakes respond when the pad first makes contact with the disc.
Power deals with how easy you can overwhelm the tyre's traction
Progression deals with pedal input to actual braking performance
Modulation deals with how easy it is to control the brake system

With well dimensioned lower pad pressure brakes with little to no servo assistance you get moderate bite, lots of power with liner progression & easy modulation. On a braking system with heavy servo assistance & high pad pressers which delivers the same ultimate braking power you'll get very good to overwhelming bite however progression will be fairly close to an inverse log curve (or if the servo is too small it can wander towards inverse exponential curve! I'd only expect to see this on cars with aftermarket brake kits however) & a reduction in fine control when modulating the brakes.

 

[funnymummy]

I had a Renault Meagne Scenic (Y reg) until March of this year, she was a nice car to drive, never had any problems with the braking, I have several large multi-lanes rabs near me, I get to do an emegency stop at lesat once a day as some tit realise at the last second they in totaly the wrong lane!! I always thought the brakes on my Renault were pretty good - Well I never hit anyone LOL!
Then I bought a Ford Grand C Max... I nearly went throught he windsreen first time I had to put the brakes on hard!

 

[fimm]

What bit do you want expanded on? I'd break down the performance of brakes into 4 categories:

Bite deals with how the brakes respond when the pad first makes contact with the disc.
Power deals with how easy you can overwhelm the tyre's traction
Progression deals with pedal input to actual braking performance
Modulation deals with how easy it is to control the brake system

With well dimensioned lower pad pressure brakes with little to no servo assistance you get moderate bite, lots of power with liner progression & easy modulation. On a braking system with heavy servo assistance & high pad pressers which delivers the same ultimate braking power you'll get very good to overwhelming bite however progression will be fairly close to an inverse log curve (or if the servo is too small it can wander towards inverse exponential curve! I'd only expect to see this on cars with aftermarket brake kits however) & a reduction in fine control when modulating the brakes.

Thank you.

There are lots of terms in there that I don't understand like "servo assistance" and "pad pressers". However I suspect that if I am interested enough I should just google "how do car brakes work?" and that would probably answer my questions! It was more that I thought you were saying that there are "better" (or would "more skilled" be a more appropriate term?) and "worse" ways of braking and I wondered if there was something I could learn from that.

My Mum's car was, yes you've guessed it, a Polo. Long gone - since they retired my parents have gone back to having one car.

 

[GrasB]

Thank you.

There are lots of terms in there that I don't understand like "servo assistance" and "pad pressers". However I suspect that if I am interested enough I should just google "how do car brakes work?" and that would probably answer my questions! It was more that I thought you were saying that there are "better" (or would "more skilled" be a more appropriate term?) and "worse" ways of braking and I wondered if there was something I could learn from that.

My Mum's car was, yes you've guessed it, a Polo. Long gone - since they retired my parents have gone back to having one car.

Okay simple stuff,
'servo assistance' is a mechanism that increases the effective force you're applying to the brakes when you put your foot on the brake pedal
'pad pressure' is how hard the pad is being pushed against the disc

Most people when they brake very hard just jam their foot against the brake to a certain level & hold it there... this may or may not lock the brakes or trigger the ABS. If you take electronics aids out of the equation & start to 'feel' what's going on you can get to the point where the main braking wheels are ever so slightly locking up (tyres give the most traction at around 20% slip). When you have the brakes which make this happen at a low enough foot pressure to allow easy modulation & a predicable modulation response of the brakes you can out brake any production car electronic braking system ('racing' ABS systems will stop you faster but they work in a slightly different way to production car ABS systems). Obviously doing this takes practice which involves time & a fair amount of money - you're going to eat tyres, discs & pads not to mention a lot of fuel from all the acceleration required to get up to speeds you can easily practice these techniques at. Then factor in the cost of getting access to a large open area of tarmac to drive on.