Thinking of trading in the 350Z...
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While I agree those are great when people panic (as most people never learned what to do in a hairy situation), they can only lessen the risk when the driver just pounds the brakes and freezes._xxx_ said:
I've yet to experience a system that "does the right thing", when the driver doesn't.
Edit: just saw your post, Sage. That's exactly what I mean.
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DiGuru said:
yeah, of course mine is a C-class so might not have everything that the shiny new M has. But, I have learned that I can trust the car to do whats best when I tell it "STOOOOOP!!!" whereas I do not trust myself to handle the situation as well. Of course, paramount to relying on the car is making sure that the system is always in good working order! But, yes, it has saved my life more than once (and only one time because I was being stupid and it would have been my own fault!)
Yes, and that's why they have all that stuff. But it's like airbags: wear your safety belts, and you won't really need them.
There actually are other things you (the driver) can do when things go bad than slamming the brakes. Often, many. Stopping as soon as possible is quite often not the best course of action. For starters, you rely on the car and driver behind you (and the one behind that, etc) to be equally good at it.
That's the difference between passive and active safety.
Being able to act on the verge of an emergency means, that your car needs to be able to transfer the forces you ask of it onto the road. And that is where you want and need ABS (and suspension that never loses it's grip). Going all-out on a straight, dry road only requires the money to buy a faster car. Most other things require a driver who knows what to do and a car that has the traction to match.
There actually are other things you (the driver) can do when things go bad than slamming the brakes. Often, many. Stopping as soon as possible is quite often not the best course of action. For starters, you rely on the car and driver behind you (and the one behind that, etc) to be equally good at it.
That's the difference between passive and active safety.
Being able to act on the verge of an emergency means, that your car needs to be able to transfer the forces you ask of it onto the road. And that is where you want and need ABS (and suspension that never loses it's grip). Going all-out on a straight, dry road only requires the money to buy a faster car. Most other things require a driver who knows what to do and a car that has the traction to match.
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Yeah, but not b/c of weight.radeonic2 said:I've never seen a heavier car outbrake a lighter car in a race
It is b/c who is going to put on super high performance brakes for a dump truck? Sports cars are supposed to be zippy, dump trucks are supposed to go slow and be tough.
So it is more a symptom of the % spent on brakes for a car I suppose, but the friction between the tire and road is cancled out by the weight increase.
Um no they don't sir.DiGuru said:
They have superior grip to put the power down, but not handling.
AWD does nothing at all for handling, thats down to the suspension and balance of the chassis.
If handling to you is the ability for you to put your foot down without having crazy oversteer, then sure, but that's more like corner exit stability/grip.
In addition a lot of AWD cars are FWD based with a viscous coupling center diff so they're FWD until the front wheels slip and have a 50:50 split so the front end will always run out of traction before the rear when accelerating unless you set i up it so the car nearly spins out when cornering on decel or just going the same speed.
Note- the wrx sti allows you to choose to splits (DCCD), 35:65 is my style since it acts primarily RWD.
and the 05's got a torsen diff in the center in addition
The 911 AWD models are RWD until the rear wheels slip btw.
A front engine AWD system will have similar weight distro to that of a FWD car.. nose heavy.
I might like a sti in 35:65 mode if I'm learning the track (you should do track events with such a car) since I'd be less likely to spin out, but ultimatly I'd like a mid engine car, or rear engine.
Now for doing rally events I of course would chose a AWD model since you really need the extra traction, on the dry it's only good for insane launchs and power on corner stability.
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Btw, about ABS: when it kicks in on snow, ice, mud or very wet roads, it actually works against you being able to control the car, and increases the stopping distance quite a bit. While it will increase the traction of the front tires, it will also create a lubricating surface in between the tires and the road every time it disengages. It would be much better (but also much more complicated) to have brakes that will never lock the wheels.
Then again, you can do that yourself.
Then again, you can do that yourself.
ShootMyMonkey
Veteran
Nonetheless, more weight = more kinetic energy while moving and more inertia = more momentum as you mentioned. That means there's more energy to overcome in order to stop.
DiGuru said:
well, first off I'm talking about the entire system- ie traction control / anti-slip programs. Secondly, I've never been in a situation with my current car that when I made use of the brake assistance there were other options... when you're on a 10-lane interstate running right through the middle of the city at 80mph and you crest a hill to see traffic STOPPED the only thing you can do is hope that your car stops soon enough that if anyone gets rearended its you and not the guy in front of you. Of course, I'm usually far enough in front of all the other cars that they have plenty of time to stop also :smile:
I think handling consists of multiple parts, that all boil down to traction (ie: being able to get the forces you apply to interact with the road). Next to your brakes and steering, putting the power on the road is one of the things you can do. And when you steer too much and your front tires lose grip, with AWD you can still apply power onto the road.radeonic2 said:
And the ability to enter the corner, and to be able to power out of it by throwing your rear (controlled, as opposed to RWD) as well.
Agreed. But the only (mechanical) system known that can really split the torque where you need it and not suffer any wheel spin is very heavy and expensive. And the visco-couplings do work very well. Nobody has as yet been able to build a computer-controlled system that does better.
While I agree in theory, it depends on many things. A system that distributes forces dynamically can and does give you the traction where you need it most at that moment, depending. When you're running on a very slippery surface, locking all the differentials is better than most other options. (And btw, I did rally plenty with some of those cars, although not the wrx when I was behind the wheel, yet.)Note- the wrx sti allows you to choose to splits (DCCD), 35:65 is my style since it acts primarily RWD.
and the 05's got a torsen diff in the center in addition
The 911 AWD models are RWD until the rear wheels slip btw.
A front engine AWD system will have similar weight distro to that of a FWD car.. nose heavy.
I might like a sti in 35:65 mode if I'm learning the track (you should do track events with such a car) since I'd be less likely to spin out, but ultimatly I'd like a mid engine car, or rear engine.
Agreed.
Well you can have tons of grip but if your suspension is too soft it's not gonna be vary fun for S turns and the like.DiGuru said:
Well depending on the tires and amount of power on tap RWD can be controlled.
Not race cars since the rubber is so grippy and usually isn't vary dynamic for its grip level.
Agreed
Agreed again
I wanna rally a proper AWD car some day
Me too. Although I did plenty and owned a non-turbo Impreza (without a cage, but that didn't hold me from going for it all out ;-) ), I really want to try out one of the bad boys on a track with me behind the wheel instead of sitting next to it. A WRX STi being first.radeonic2 said:Agreed again
I wanna rally a proper AWD car some day
Where do you live where you get access to erm.. "tracls".DiGuru said:Me too. Although I did plenty and owned a non-turbo Impreza (without a cage, but that didn't hold me from going for it all out ;-) ), I really want to try out one of the bad boys on a track with me behind the wheel instead of sitting next to it. A WRX STi being first.
At the moment, I've got a 13 year old Hyundai Lantra 1.6 Sportivo, (no money, and I needed a cheap and reliable car...), which handles pretty nice on roads (114 PK, which is more than about 90% of the cars around here), but is really bad for dirt roads. The suspension is just awful when getting off-road. Let alone going through and cornering really -Anything- with 90 km/h, like with the Impreza.radeonic2 said:
Which is what I did pretty often: if the weather was bad, take my car (especially the Imprza, of course!) out to some stretch of nowhere, and see how fast I could travel the worst roads. LOTS of fun!!!
And I know some people who did rally for a living, one of them with a pumped Impreza. They do what I do much better and faster, but mostly because that car is just so much better. I really want one as well, so I can do that also!
I know some people with Audi Quattro's and other rally cars (like a V6 AWD Mini and such ;-) ) as well, but that isn't generating the same amount of adrenaline by far. The suspension and handling of those Impreza's is just so much better, it's insane. They react instantly, stick to any surface, and are really forgiving.
I started out with this in the army, driving a Jeep. I build quite a reputation of being able to go anywhere, fast. And I still never got any car stuck whatsoever, in any terrain, not even the Peugeot 206.
What's a "PK"DiGuru said:At the moment, I've got a 13 year old Hyundai Lantra 1.6 Sportivo, (no money, and I needed a cheap and reliable car...), which handles pretty nice on roads (114 PK, which is more than about 90% of the cars around here), but is really bad for dirt roads. The suspension is just awful when getting off-road. Let alone going through and cornering really -Anything- with 90 km/h, like with the Impreza.
Which is what I did pretty often: if the weather was bad, take my car (especially the Imprza, of course!) out to some stretch of nowhere, and see how fast I could travel the worst roads. LOTS of fun!!!
And I know some people who did rally for a living, one of them with a pumped Impreza. They do what I do much better and faster, but mostly because that car is just so much better. I really want one as well, so I can do that also!
I know some people with Audi Quattro's and other rally cars (like a V6 AWD Mini and such ) as well, but that isn't generating the same amount of adrenaline by far. The suspension and handling of those Impreza's is just so much better, it's insane. They react instantly, stick to any surface, and are really forgiving.
I started out with this in the army, driving a Jeep. I build quite a reputation of being able to go anywhere, fast. And I still never got any car stuck whatsoever, in any terrain, not even the Peugeot 206.
Nice army story dude:smile:
Which of course doesn't mean you are correct, but I hope you feel betterradeonic2 said:I knew someone else was gonna back me up
It is really extremely simple.
Frictional force is proportional to (normal force)*(coefficient of friction)
Ok got that, so there it is clear that the weight makes no difference, b/c it is directly proportional to friction.
So what do you change?
The coefficient of friction between the tire and the rubber, you can either change the road surface i.e. "it is snowing oh shit a tree" or the tire compound the rubber.
Now what else effects the braking distance?
The friction between the rotor and the pad. How do you change this?
Same answer, you can change the pad compound, but you have to balance heat with stickiness i.e. the kinentic energy turns into heat. Or you change the force applied on the caliper. Or of course both. Now look at the brakes on a sports car they will be very big in proportion to the weight, the main purpose is really for durability, predicitability and heat dissapation. Think how big such a brake is ona 700kg car then compare to a 5000kg truck, what happens? The brakes would have to be giant, so what do they do instead? They change the braking system so it is less effective which means it can be smaller and will have to dissapate less heat in a given amount of time. Otherwise they would need to cool the brakes with liquid or something radical. Some cars have rotors designed to push air through the brakes and cool them btw.
Then the bit about anti lock brakes and/or doing it yourself. Why does this work better?
There are two coefficients of friction, static and kinentic. Kinetic is when something is sliding and it is always less than static. When your tire is rolling properly you are taking advantage of static friction, thus if it ever slides the frictional force decreases suddenly and dramaticly. ABS attmepts to assure this never happens. Threshold braking does the same except you do the thinking instead of a computer. I have found that a good abs system actually does a very decent job, but crappy ones just do not come close to what a person can do. Oh and btw and dry pavement ABS does most of the work on the rear tires b/c when you slam on the brakes the weight is transferred forward by the inherent moment about the cars center of gravity, so the front tires are less likely to slip than the back tires.
Then you do have the suspension and traction control et. al. Well here is where I would say it gets much more tricky. Basically you get the tons of variables that were spoken of earlier, but if it is in a straight line this bit isn't to important, of course what fun is driving in a straight line?
On the topic of controllable skids I would say either an AWD car or a RWD car just pounds the daylights out of FWD as you said. I have found my WRX handles very nice in a skid though my wife does not appreciate that fact
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I too want to mess around with our wrx when we get older and have money, it should be very fun to throw in the sti tranny, and some new engine in 100,000 miles.
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