Inefficient brakes

[Hope4Sun]

Bizarre.  Can't really think why braking gently would cause increased brake wear.  The last two cars I had managed to never need any brake changes and managed 75000 and 63000 miles respectively.

I thought so too, i think the rust did not help on the back of the discs, but the discs are quite soft according to the Toyota guy and i'd been wearing them down along with the corrosion , only had 15k on the clock and took it in for an oil change. Only cost me some new pads, so did not complain

Andy

[Anonymous]

Phil4 wrote:

But a volvo is built like a tank. It doesn't need good brakes

Errr......don't you kinda think that is the point? Cos it IS built like a tank, it should have BETTER brakes cos something like that, which is so bulky and heavy, regardless wither it will protect you in a crash or not (they are no longer the safest cars on the road), then you need good stopping brakes to stop the weight and bulk.

I was half joking (and forgot the smiley).

[Anonymous]

One of my pet hates at the moment is the number of kn*bheads on the road that seem to think they can out-brake an MR2

It amazes me how many people seem to think they're reactions are quick enough to drive 2ft from the bumper of pretty much any car.  

But as you say, playing that game with a '2 is just mental, 'cause they'll just end up making a mess of things (seen two close examples of that, and haven't been driving it too long).

Unforunately from what I've heard insurance isn't quite as clear cut on being rear-ended now.  It used to be that if the person behind ran into you, regardless of why, they were responsible.  Now it seems to be 50:50 far more often.  Which isn't really on.

[zud]

Unforunately from what I've heard insurance isn't quite as clear cut on being rear-ended now.  It used to be that if the person behind ran into you, regardless of why, they were responsible.  Now it seems to be 50:50 far more often.  Which isn't really on.

I hadn't heard that.  I was rear-ended last year (in my previous car), and my insurance company never seemed to have any doubt that the other guy was to blame.  But I've long since thought that there are situations when it's not quite so clear cut... if someone pulls into the gap in front of you on a motorway, just as the car/lorry that was if front of you starts to brake, then you're suddenly left with half the braking distance through no fault of you're own! Maybe the insurance companies are looking at this kind of thing in more detail???

[Anonymous]

I think they are looking into it more, but if you've not got any witnesses, it could get quite interesting.

[Anonymous]

I find that when I leave the safety gap on the motorway, there is always some fool that seems to think I have left the gap for them to pull into, thus me being on their ass.

Just been driving a Nissan Nivara Truck in Cyprus...a lot of fun, and NO traffic there...although the off road mountain roads where hairy!

[Anonymous]

Phil4 wrote:

I was half joking (and forgot the smiley).

Ahhhh......sorry Phil. My misinterpretation! Oh well, I look like and arse now and I take it all back..............  s:oops: :oops: s:oops:    s:oops: :oops: s:oops:    s:wink: :wink: s:wink:    s:D s:D

[Chris]

Well, I've been out with Martin 'last of the late breakers' Holden today at Keevil, and can assure you that the roadster does have some seriously impressive brakes (to go with the equally impressive turbo!) - we caught so many cars under braking it was untrue!  Mind you, they only lasted about 10 laps a time due to the heaving hammering they got twice a lap!   s:lol: :lol: s:lol:    s8) s8)

[Anonymous]

Does anyone else here find the ABS intrusive? I'm a little bit worried when braking hard because the ABS seems to cut in earlier than I'm expecting.  s:( s:(  

I'm not a driving god, but I'd expect to feel the car lose a little bit of traction before it kicks in. It certainly does in my wifes FIAT. Has anyone else found this?

The annoying thing is that the braking distance obviously extends when it goes ABS (but does give you more control)

[Anonymous]

I find the ABS kicks in before the car skids, but that's what I was expecting.  In the dry I really struggle to get the ABS into action in a straight line, it really has to be a rough road, otherwise the car just stops.

In the wet it's far easier to trigger the ABS.

[Anonymous]

Ive not had my ABS kick in unless i forced it to... my car stops exactly when i want it to.   s:D s:D

[Anonymous]

Does anyone else here find the ABS intrusive? I'm a little bit worried when braking hard because the ABS seems to cut in earlier than I'm expecting.  s:( s:(  

I'm not a driving god, but I'd expect to feel the car lose a little bit of traction before it kicks in. It certainly does in my wifes FIAT. Has anyone else found this?

The annoying thing is that the braking distance obviously extends when it goes ABS (but does give you more control)

ok lemme try and explain this for you, i'm crap at explaining.

ABS is not about stopping, its about controlling.  ABS keeps the wheel in motion and stops it locking up.  If your ABS is coming on then you would have been skidding without it, the brakes on the MR2 are some of the best in the world (did you know we stop as fast as a McL F1, yes REALLY!) so the best way to make our brakes better is to fit tires with more grip.

[zud]

I'm no expert on ABS, but believe there are two types.  I'd guess the Fiat uses a mechanical system (like my old Escort), where the brakes have to lock before the mechanical system releases them.  But (I think) that electronic systems are tuned to kick in just before the wheels lock.

Also, my understanding of ABS is that it should apply as much braking pressure as possible without the wheels locking.  With "manual" braking, the stopping distance is extended as soon as the wheels lock, so you'd be hard pushed to beat ABS.... I think.... but I'm happy to be corrected on this!

[Anonymous]

[(did you know we stop as fast as a McL F1, yes REALLY!) so the best way to make our brakes better is to fit tires with more grip.

Thought I'd check this out, and the F1 takes 127ft, the MR2 121ft.  

Max Lateral G's are also higher in a '2, 0.86g in an F1, 0.88g in an MR2.

And then in a slalom, we're still faster, 66.1mph in an MR2 verses 64.5mph in the F1

Obviously though we lose out big time when it comes to acceleration.

[Anonymous]

you'd be hard pushed to beat ABS.... I think.... but I'm happy to be corrected on this!

I'm not sure about this.  I think under certain circumstances a skidding tyre will stop you more quickly (stright line, smooth road, dry).

The purpose of ABS as WD has pointed out is not about the stopping, but the steering.  With ABS you can turn and break on the limit at the same time, say to swerve.  Without, you'd plow straight in to the thing you're heading for.

[Anonymous]

you'd be hard pushed to beat ABS.... I think.... but I'm happy to be corrected on this!

I'm not sure about this.  I think under certain circumstances a skidding tyre will stop you more quickly (stright line, smooth road, dry).

Correct; maximum traction equals maximum friction, which occurs in a full 4-wheel lockup (assuming a dry road). If you want to stop in the shortest distance possible, then ABS won't help you, but usually you tend to want to try and combine the stop with some avoidance tactic...

[Anonymous]

Since I started this thread I have realised that I'd not been driving fast enough to heat up the disks. By speeding up on an open road and then braking sharply makes a world of difference. I still say that after washing the pad carbon off the brakes are sharper.

MrT offered to contribute 50% of the parts cost for disk replacements, but I politely told them through my dealer to stick their offer where the sun doesn't shine  s:!: :!: s:!:    s:!: :!: s:!:    s:!: :!: s:!:   s:!: :!: s:!:  

At the moment I am trying to get hold of the Halfords silver manifold paint to use on the calipers and disks. One of their superstores only seems to have black in stock.

  s:) s:)    s:) s:)

[mph]

I think under certain circumstances a skidding tyre will stop you more quickly.

Under all circumstances, a tyre will provide the its peak traction when it is slipping by ~8%*.



*Or maybe 11%. I wasn't really paying attention during the lesson.
Hmm, thinking about it, maybe 11 was the optimum slip angle and 8 the slip traction. Anyone care to remind me?

[zud]

you'd be hard pushed to beat ABS.... I think.... but I'm happy to be corrected on this!

I'm not sure about this.  I think under certain circumstances a skidding tyre will stop you more quickly (stright line, smooth road, dry).

Correct; maximum traction equals maximum friction, which occurs in a full 4-wheel lockup (assuming a dry road). If you want to stop in the shortest distance possible, then ABS won't help you, but usually you tend to want to try and combine the stop with some avoidance tactic...

Being an old git, I learnt to drive before ABS, and was taught to pump the brakes in the event of a skid.  And I know for certain that in wet/icy conditions that you stop more quickly when the wheels aren't locked.  So I took a look at Howstuffworks.com as they usually have some good explanations for this type of thing.  There's too much to repeat here, but here's a key part of their description under brakes...

Friction  "An interesting thing about friction is that it usually takes more force to break an object loose than to keep it sliding. There is a coefficient of static friction, where the two surfaces in contact are not sliding relative to each other. If the two surfaces are sliding relative to each other, the amount of force is determined by the coefficient of dynamic friction, which is usually less than the coefficient of static friction.
For a car tire, the coefficient of dynamic friction is much less than the coefficient of static friction. The car tire provides the greatest traction when the contact patch is not sliding relative to the road. When it is sliding (like during a skid or a burnout), traction is greatly reduced."

It's a great website, with loads of explanations about a wide range of subjects (assuming they know what they're talking about!)....

http://auto.howstuffworks.com/brake.htm

[Anonymous]

Hmm, that's completely at odds with what I was taught at my driving school day at Castle Coombe. Curious...

I was doing a skid control course, and was told that if I wanted to brake fast, but keep control of the vehicle, then pumping the brakes was good. However, if I just wanted to brake fast in a straight line, then I should brakes as hard as possible, even if that meant locking up. Icy/oily conditions I think are completely different. Something about tire tread I believe.

Great F1 drivers from the 60's (think Moss and Hill, all you GPL fans) used to be able to do something called trail braking. That's where you brake late, while turning into a corner, using engine braking to help as well. What they used to do was brake so that the tires were almost locking up (they had a term for it, can't remember. Anyone?). That's supposed to be the most efficient way of braking, according to my instructor  s:? :? s:?  

BTW, I though ALL ABS was mechanical? It just quickly jumps the brakes on and off doesn't it? In the '03 '2s you've got braking assistance as well which modulates the brake power going to each wheel (as Mr T showed at Brands Hatch in a Corolla  s:) s:)  )

Anyway, the point I was trying to make earlier is that I think the ABS cuts in too early on my '02 '2. I'm pretty sure theres more braking power to be had... it just seems the ABS cuts in. And I can definately feel the braking distance increase when it does.

Sorry about the long, rambling post   s:oops: :oops: s:oops:

[Anonymous]

just thought i would say that i had to stamp on my brakes this morning when a light decided to turn red on me (approching at 80...90ish... i mean 70 officer...   s:roll: :roll: s:roll:  ) and the '2 stopped dead in its tracks... no ABS kicked in and i was well impressed!   s:D s:D

[zud]

Hmm, that's completely at odds with what I was taught at my driving school day at Castle Coombe. Curious...

Curious indeed!... At one extreme (ice/oil) I think we agree that pumping the brakes/ABS is better, but maybe at the other extreme (dry, flat tarmac) the friction between a locked tyre and tarmac is better than a braking but turning wheel?  That's not what I've always been led to believe, but who am I to argue with a driving school!!

BTW, I though ALL ABS was mechanical? It just quickly jumps the brakes on and off doesn't it?.

The "pumping bit" is all mechanical, but I think there are different versions of the "detecting bit"... my escort needed the wheels to actually lock momentarily before it released them, whereas I think the more modern systems attempt to detect that the wheels are about to lock and releases them.  Maybe this could explain why/how your ABS kicks in early?  Could the system misjudge when the wheels are about to lock and release them too early?  Could the system be fooled by mods to wheels/tyres/suspension?
 
Likewise, sorry about the long, rambling post   s:oops: :oops: s:oops:

[Anonymous]

I can't vouh for anything too technical, but they guy at Brands Hatch the other week said that  cars fitted with ABS will always stop in a shorter distance under extreme provocation than those that do not have it. Skidding is the bain of a driver, not just because of the loss of contol, but it also slows you down in all the wrong ways. Skidding means that the contact patch is not "working" or "in contact"  with the road as it should be. ABS will keep the wheel spinning and thus allowing the tyre to grip more efficiently and therefore make the car slow down quicker.

Like I said, there are more technically minded people about this kinda thing than me on this forum, but I can't see the logic in saying a car will slwo down quicker when skidding. Surely in every case, when thinking about this logically, that is just not true. I would want the tyre to be in "contact" (I know it is in contact while skidding, but I think you all know what I mean) at all times rather than slipping and sliding about all the time. Why do driving istructors and examiners on your driving test ask you to do an emergency stop without skidding? I took my test pre-ABS on cars and I was ALWAYS told that preventing the front (or rear) tyres from skidding not only gave you control over the car, but also helped you stop quicker.

I can't see where there is an argument here.....

[Anonymous]

I can see what you're saying, but surely the fact that rubber has to be stripped from the tyre would disipate more energy (which is what slows you), than a tyre not doing so?

[Anonymous]

Anyway, the point I was trying to make earlier is that I think the ABS cuts in too early on my '02 '2. I'm pretty sure theres more braking power to be had... it just seems the ABS cuts in. And I can definately feel the braking distance increase when it does.

Like I said, ABS has nothing to do with braking and everything to do with control.  If your ABS is coming on you've lost traction, a average driver can't control a wheel that has lost traction and making a car skid so the ABS keeps the wheel turning.

To answer your question (Unless something is very very wrong with your ABS) if the ABS is cutting in then your car without it would be losing traction, I'm taking a guess that your a normal/average kinda driver (I don't mean this in a bad way its just none of us are Richard Burns) so you'll have much much more control with the ABS on.  If you want to stop the ABS coming on then you need to stop your car losing traction, and upgrading the tires is the 1st and most important step.

Just as a note, as a racer I PREFER ABS and I know other racers that prefer it on as well.  Also from what i've seen ABS cars will stop much faster, thinking about it I also remember Driven on C4 testing that.  Racers don't have ABS because the car stops faster without it, its for other reasons (like slides in rallies etc...)