Alan Baker
On 2014-02-24 19:57:00 +0000, David Fritzinger said:

David Fritzinger
In article <leg1l4$pp$1@news.datemas.de>, Alan Baker <alangbaker@telus.net>wrote:

Alan Baker
On 2014-02-24 17:54:42 +0000, David Fritzinger said:

In article <lec4ff$qrk$2@dont-email.me>, "Brake Dive, Acceleration Squat, Body Roll Works LLC" <isquat@gmail.com>wrote:

On 2/22/14, 18:41, -hh wrote:

On Saturday, February 22, 2014 10:05:42 AM UTC-5, Nashton wrote:

On 2014-02-21 12:49 PM, Brake Dive, Acceleration Squat, Body Roll Works LLC wrote:

Right, they fixed the ride, but now you've got problems with the fucking understeer, cause the fucking thing got fwd.

You mean torque steer.

No, he means understeer, although not necessarily for the reason he claims.

When you get at least 50% of torque to the rear axle it's a piece of cace to rotate the car once you will have turned ESP off.

So yes I meant understeer in the drivetrain layout context. Though subaru with it's outgoing symmetrican layout is notoriously unwilling to rotate. I guess it's a moot point in a pig such as Q7.

FWIW, in many cases you can get oversteer in a FWD car by cutting back on the throttle in the middle of a high speed turn, when understeer is raising its ugly head. Of course this varies from car to car, depending on how the manufacturer has set up the suspension and on how good the car's grip is.

Correct: trailing throttle oversteer.

It won't be as bad as it would be in a RWD car, because the fact that the engine braking operates on the front wheels rather than the rear means that the reduction in traction operates against the oversteer rather than adding to it.

David Fritzinger
I think that some drivers (race and rally drivers come to mind) actually want oversteer, and prefer rwd to fwd because the oversteer is more controllable and is induced accelerating through a turn gives you more speed coming out of the turn. I believe that in Porsche 911s (until recently), and especially in 911 Turbos, the only way to safely drive the car on a twisty road was to enter the corner relatively slowly, and accelerate hard on the way out. Any other technique would put you in the bushes, backwards. That the modern 911s handle so well is an excellent example of engineering over physics.

Alan Baker
You're absolutely correct: race and rally drivers want to be able to use both the brakes and the throttle in order to steer the car, and RWD offers a better layout for doing that.

As for oversteer being induced by accelerating, that's incomplete.

Typically, a racing driver wants some oversteer on corner entry, which is induced by trail braking or trailing throttle. With trail braking, you get to maximum braking, and then ease slowly off the brakes while you're steering into the corner. That means that at any instant, there is more load on the front tires than is necessary for the braking (because it takes time for the springs to decompress). Trailing throttle creates the same effect: deceleration transferring load forward, and also removes traction budget from the rear tires (if RWD of course) because they're the ones doing the decelerating.

Then after the first phase, you go to a little throttle to get back to a neutral handling balance, followed by increasing throttle as hit a late apex and start unwinding the steering. This usually creates a slight understeer, but by now you've got the car pointed where you want to go. Of course, apply too much throttle in a RWD car and you'll use up the entire traction budget, and you'll get oversteer in a hurry.

With FWD cars, because trailing throttle isn't as effective at moving the handling balance towards oversteer (because the forward load transfer's effect is counteracted by the front tires traction budget being used up doing the decelerating) the use of trail braking to rotate the car is more emphasized and you attempt to get all the turning done earlier, so that when you get on the throttle for exiting the corner there's not much turning left to be done, because understeer--lots of understeer--is all you get once you're accelerating.

And with earlier Porsche 911s, there was a fine line to walk. Their weight balance, and suspension geometry contributed to oversteer under trailing throttle. So the advice wasn't so much that you had to accelerate hard on the way out, but more that you just shouldn't back off. Accelerating hard--particularly the Turbos--could also use up the entire traction budget of the rear tires and that would spin you off as well.