4wd and Roadcraft
Discussion
Afternoon all!
I am shortly (Inshallah) taking possession of a 4.2L Quattro Audi A8. I've completed a 3-week Police response driving course, but am given to understand that there is a slightly different method of driving required with 4wd cars, particularly of the powerful variety.
Any particular pointers, especially with regard to cornering and skid correction? My accepted method is to enter the corner at a resaonable speed and maintain that speed with light acceleration through the corner.
I am shortly (Inshallah) taking possession of a 4.2L Quattro Audi A8. I've completed a 3-week Police response driving course, but am given to understand that there is a slightly different method of driving required with 4wd cars, particularly of the powerful variety.
Any particular pointers, especially with regard to cornering and skid correction? My accepted method is to enter the corner at a resaonable speed and maintain that speed with light acceleration through the corner.
I think the rule of doing your braking in a straight line, getting your speed & gear right before you enter the bend, constant throttle through the bend and accelerate out still applies, even with 4WD.
"Slow in Fast out"
Where I think some go wrong is believing 4wd makes you invinsible, and that your car can not be unstuck from the road, but what it really means is when you do crash it's a much bigger crash !!
I learnt in the recent snow that the 4wd is very handy for getting you going, but not much help when trying to change direction or stop.
"Slow in Fast out"
Where I think some go wrong is believing 4wd makes you invinsible, and that your car can not be unstuck from the road, but what it really means is when you do crash it's a much bigger crash !!
I learnt in the recent snow that the 4wd is very handy for getting you going, but not much help when trying to change direction or stop.
The torque split of your centre diff, can have a differance in the way you drive a 4WD, a larger split to the rear means it will drive more like a rear wheel drive and vica versa.
However the biggest rule I have found with 4WD is when you start sliding or losing grip is to always, always, power out. Never come off the power, that when you run the risk of spinning or under sterring off.
However the biggest rule I have found with 4WD is when you start sliding or losing grip is to always, always, power out. Never come off the power, that when you run the risk of spinning or under sterring off.
Boost Junkie said:
The torque split of your centre diff, can have a differance in the way you drive a 4WD, a larger split to the rear means it will drive more like a rear wheel drive and vica versa.
However the biggest rule I have found with 4WD is when you start sliding or losing grip is to always, always, power out. Never come off the power, that when you run the risk of spinning or under sterring off.
However the biggest rule I have found with 4WD is when you start sliding or losing grip is to always, always, power out. Never come off the power, that when you run the risk of spinning or under sterring off.
Carreauchompeur said:
Afternoon all!
I am shortly (Inshallah) taking possession of a 4.2L Quattro Audi A8. I've completed a 3-week Police response driving course, but am given to understand that there is a slightly different method of driving required with 4wd cars, particularly of the powerful variety.
Any particular pointers, especially with regard to cornering and skid correction? My accepted method is to enter the corner at a resaonable speed and maintain that speed with light acceleration through the corner.
The most stable and grippiest state for a car to be in in a corner is with just enough throttle to counteract the drag of cornering, which is known as a "steady throttle". If you accelerate, then the car will tend to understeer, and if you back off or coast the car will tend to oversteer (it might not actually do either of course, but the handling balance will "tend" towards these directions). The safest and mechanically kindest way to drive is with the car balanced between these states. This way, if you need to take avoiding action in a cornering or come across mud, gravel or oil the car is best placed to react in a safe and predictable manner.I am shortly (Inshallah) taking possession of a 4.2L Quattro Audi A8. I've completed a 3-week Police response driving course, but am given to understand that there is a slightly different method of driving required with 4wd cars, particularly of the powerful variety.
Any particular pointers, especially with regard to cornering and skid correction? My accepted method is to enter the corner at a resaonable speed and maintain that speed with light acceleration through the corner.
In addition to this, at low speeds or in low grip situations, power can cause the driven end of the vehicle to break away. With front drive the effects I mentioned just now (acc = u/steer & de-acc = o/steer) are exacerbated, and in rear drive they are reversed. With virtually all four wheel drive road cars you'll rarely get power affecting grip in this way unless it's snowing or raining and you're really brutal. I doubt the A8 would ever be affected much by power in this way, given it's size and modest power (~300bhp?).
Of course, if you stuck a couple of turbos on it, you might well need to worry about traction a bit more 
In the mean time, quick getaways turning out of junctions, oil, mud, aquaplaning and loose surfaces will be your biggest problem areas.
Roadcraft is about good car control (amongst other things) and getting to know how you car handles at the limits of adhesion is good practice if done away from hazards.
Enjoy that V8!
In the mean time, quick getaways turning out of junctions, oil, mud, aquaplaning and loose surfaces will be your biggest problem areas.
Roadcraft is about good car control (amongst other things) and getting to know how you car handles at the limits of adhesion is good practice if done away from hazards.
Enjoy that V8!
Go visit Ingolstadt 
The thing with 4WD is that it gives increased traction but not adhesion. Being nose-heavy the Audis tend to understeer into the corner. But, once the forces on the car are stable in the corner, you can plant the throttle earlier than you would consider in a 2WD and slingshot out.
The thing with 4WD is that it gives increased traction but not adhesion. Being nose-heavy the Audis tend to understeer into the corner. But, once the forces on the car are stable in the corner, you can plant the throttle earlier than you would consider in a 2WD and slingshot out.
Zad said:
Go visit Ingolstadt
The thing with 4WD is that it gives increased traction but not adhesion. Being nose-heavy the Audis tend to understeer into the corner. But, once the forces on the car are stable in the corner, you can plant the throttle earlier than you would consider in a 2WD and slingshot out.
If the balance is right in a 2WD car the difference in acceleration is minimal in all but the slowest of bends. This is why even though 4WD has often been allowed in F1 it's never been successful. The extra weight was never really worth it.The thing with 4WD is that it gives increased traction but not adhesion. Being nose-heavy the Audis tend to understeer into the corner. But, once the forces on the car are stable in the corner, you can plant the throttle earlier than you would consider in a 2WD and slingshot out.
http://en.wikipedia.org/wiki/Four-wheel_drive_in_F...
In my honest opinion having owned cars with FWD, 4WD and RWD, 4WD is unecessary on wet or dry road tarmac. It has its uses in the snow and ice and on gravel, but that's about it. This shouldn't detract from the OP's new car though, because, like my 4WD road car (a Celica Carlos Sainz) it's other features are unique and fantastic (in the case of the A8, I refer to the lovely engine and the interior space and comfort).
RobM77 said:
it's other features are unique and fantastic (in the case of the A8, I refer to the lovely engine and the interior space and comfort).
Have finally got my hands on it and have devoted an entire day to fettling and fiddling with the various features... Have discovered the inbuilt television too. It's like driving an 155mph living room around!
If you've completed a 3 week police response course then I'd think the adjustment for a 4WD car would be minimal.
He's dead right, though. They'll still lift-off-oversteer so keep some power through the wheels, during cornering - as you would when balancing a RWD.
Carreauchompeur said:
Boost Junkie said:
The torque split of your centre diff, can have a differance in the way you drive a 4WD, a larger split to the rear means it will drive more like a rear wheel drive and vica versa.
However the biggest rule I have found with 4WD is when you start sliding or losing grip is to always, always, power out. Never come off the power, that when you run the risk of spinning or under sterring off.
However the biggest rule I have found with 4WD is when you start sliding or losing grip is to always, always, power out. Never come off the power, that when you run the risk of spinning or under sterring off.
I think it's more helpful to think about weight transfer and balance than 'lift off oversteer' etc. A 4WD car will react to acceleration and deaceleration in a corner like any other car: accelerate and a tendency to understeer occurs, deacelerate and a tendency to oversteer occurs. The ideal cornering situation is a balance between these too.
There's obviously a lot more to cornering than that, but I think that's a good basic starting point.
There's obviously a lot more to cornering than that, but I think that's a good basic starting point.
Edited by RobM77 on Monday 25th May 09:25
WhoseGeneration said:
RobM77 said:
It has its uses in the snow and ice
Perhaps, although on a downhill, off camber road, on ice, with "summer" tyres, maybe not, in my experience. I did manage to point the front away such that only the ns of the rear bumper kissed a parked car. 
I expect any car would struggle in those circumstances, but I too had a few issues with my 4WD car like this in the snow and ice. I prefer the control of RWD in those sorts of conditions (the front wheels are unhindered in steering, without power or engine braking getting in the way). However, if you need to get up a hill there's nothing like the traction of 4WD!! I spent fifteen minutes trying to cover 20 yards of hill in my BMW last time it snowed here. I thought I was stuck for good! For driving in Hampshire though I'll take what's best for the other 360 days of the year... ;-)Gassing Station | Advanced Driving | Top of Page | What's New | My Stuff