Rear Wheel Steering

[Archimedes]

So an ‘instructor’ at a Vegas ‘Wreck an Exotic’ theme park said it so you think it’s gospel?

And you think he/she/they know better than Porsche?

The stupid shit I read on this forum never ceases to amaze.

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[f1eng]

It hasn’t damaged the paint thus far but it does collect debris.

Exactly what one would expect.

 

[f1eng]

I drove a GT3RS at the Vegas exotic car track and instructor told me the same. He said If you lift off mid corner the rear wheels “unsteer” and propel the rear of the car sideways, frequently leading to a spin out and an off.

The rear suspension of the original 911 did indeed toe out on lift off but the problem was resolved by the multi link rear suspension introduced in the 1990s, with the 993, which was engineered so lift off loads caused the flexure to go towards toe in rather than toe out and 911s have been more stable ever since.
Rear wheel steer is just a more sophisticated microprocessor controlled way of doing the same thing better, plus some others too.

The multi link suspension is pretty good already though, and the days of needing the skill of Vic Elford (RIP) to drive one fast have been gone for 25+ years.

 

[f1eng]

You should stop.

I may, I found on the F1 web sites the non-technically minded fans didn't like their more ridiculous beliefs being questioned so I gave up on them altogether years ago, partly to avoid confidentiality potential when I was still a senior engineer in the business but mainly exasperation.

 

[B61]

Maybe I should stop.

Please, don't!
Your knowledge is amazing and I love to read & learn from your posts.

 

[B61]

I think this is what I am trying to say too. Just that it isn’t the end of the world if you don’t have RAS. The thread was very pro RAS. I was just trying to give it some balance.

Of course it's not end of the world... in my case, RAS helps me to park (and go out) at home without corrections. I was not able to do that with Renault Koleos...
Also, it's faster/easier when maneuvering on public parking...

 

[G7SUM]

I may, I found on the F1 web sites the non-technically minded fans didn't like their more ridiculous beliefs being questioned so I gave up on them altogether years ago, partly to avoid confidentiality potential when I was still a senior engineer in the business but mainly exasperation.

I enjoy your comments as i'm sure many others do. Please continue to share and ignore the small minority who fail to appreciate fact and real world experience.

 

[Chris H]

So an ‘instructor’ at a Vegas ‘Wreck an Exotic’ theme park said it so you think it’s gospel?

And you think he/she/they know better than Porsche?

The stupid shit I read on this forum never ceases to amaze.

God forbid if Porsche ever made a mistake………….it’s not like their engines blow up is it !

 

[gnop1950]

God forbid if Porsche ever made a mistake………….it’s not like their engines blow up is it !

A mistake that has persisted for almost a decade? RWS was on the 911 Turbo, Turbo S, and GT3 back in 2013. I wouldn't think that anyone that thinks the Porsche engineers are that incompetent would be interested in owning a Porsche.

RWS is even offered on the Lexus LC 500, Mercedes-AMG GT R and GT C, Lamborghini Aventador, Ferrari 812 Superfast, Ferrari GTC 4 Luss, BMW 5 Series, etc.

That is a lot of manufacturers that seem to believe there are advantages to having RWS, even on the track. For pure race cars, there are lots of driver aids/features that are prohibited. Both to keep the speed down and make sure that driver skill remains an important part of racing. Otherwise we might as well be watching robots race ?

 

[Jrkennedy37]

God forbid if Porsche ever made a mistake………….it’s not like their engines blow up is it !

Don’t feed the troll!

I don’t think the RAS thing I provided an anecdote about is a mistake - it’s a feature that can improve lap times and improve stability, but also requires adaptation and additional skill by the driver to fully exploit.

One thing I’m curious about now is RAS behavior on an AWD vehicle vs the rear drive track cars. There must be a different technique between the drivetrains.

 

[f1eng]

I really do think the Porsche business model guarantees software complexity and potential difficulties whereas Tesla's does not.

There are two reasons IMO, firstly Porsche have a lot of options, which means many hundreds of different potential combinations of control software depending on customer whim. Secondly quite a few of the controllers are relatively old legacy bits of software needing integrating into all the newer stuff, all potentially bug creating.

Tesla have only one major option with different sensors and control, the self driving one. Otherwise it is one relatively new bit of software conceived and developed for an EV from day one, and it is fairly simple if I understand it correctly with things like regeneration not being linked to friction brakes, so recent integrated and simple, which is a good recipe for software IME.

I detest SUVs so my choice was pretty well Taycan v Model S with the car to replace a saloon and a sports car, The Taycan was near ideal but the biggest thing against the Tesla, for me, was the plastic seats and touch controls. I don't like one pedal driving either and delivery here in the UK is long and it seemed to no longer have a steering wheel when I tried to spec one.

Mind you I don't play video games either.

 

[Chris H]

A mistake that has persisted for almost a decade? RWS was on the 911 Turbo, Turbo S, and GT3 back in 2013. I wouldn't think that anyone that thinks the Porsche engineers are that incompetent would be interested in owning a Porsche.

RWS is even offered on the Lexus LC 500, Mercedes-AMG GT R and GT C, Lamborghini Aventador, Ferrari 812 Superfast, Ferrari GTC 4 Luss, BMW 5 Series, etc.

That is a lot of manufacturers that seem to believe there are advantages to having RWS, even on the track. For pure race cars, there are lots of driver aids/features that are prohibited. Both to keep the speed down and make sure that driver skill remains an important part of racing. Otherwise we might as well be watching robots race ?

Porsche have persisted in making chocolate engines for far longer than RWS has been on the scene, according to your analogy………………why do they keep getting it wrong ?

 

[Jhenson29]

Debris going fast enough to produce road rash comes from the tyre contact not the airflow.

For the debris thrown up by the tyre to be going fast enough to cause paint damage a direct line of flight, or at most a tiny deflection, is needed. If you look at the side of the Taycan debris thrown up by the tyre would have to be going upwards at about 60 degrees to even get to the vent and not much debris ever gets thrown that steeply up and even if it was the only bit of bodywork it could hit is a tiny bit of the undercut of the door pressing part of the vent right at the front.

It sounds like your are describing the tire “throwing” the rock at a car (itself or another) but I don’t think that’s how it works. The tire isn’t (generally) moving relative to the rock at the contact patch. It only moves the rock if the rock follows the tire, and in that case, the rock will be thrown more up and forward (not back at all, actually).

Unless there is slip, there isn’t really a way for the tire to throw the rock backwards. Even then, how hard would be relative to the slip, so it doesn’t seem like it should generally be a concern.

I would think typical rock chips are caused by a car tire throwing a rock up into the air and then the energy for the chip is supplied by the car that hits the rock, not the rock itself (or tire that hit the rock).

That said, I still think the area past the vent is a low chip area. I wouldn’t go so far as to say impossible, but it’s at least somewhat difficult because the force from the car is in the wrong direction (seems like it would be nearly orthogonal to the direction of displacement to cause a chip).

At least, those are my thoughts on the issue.

 

[f1eng]

Unless there is slip, there isn’t really a way for the tire to throw the rock backwards

True, but without "slip" no longitudinal force is generated by a tyre, it is analogous with slip angle and cornering.
Optimum slip varies with tyre design and is, of course very small when cruising but only zero if coasting.

 

[Greenmachine]

I know how adamant people are but it just isn't plausible.

I don't argue whether that have a stone chip or not but just look at it, if one has even the slightest glimmer of scientific aptitude it obviously can't come about because of a stone being thrown up through the vent.

It is clearly a false extrapolation IMO.

Lots of dirt in winter though which may make it harder to wash without scratching the paint???

I have already deleted a lot of technical information fact that doesn't match common beliefs, maybe it is pointless trying since it is a known phenomenon that once people have accepted a narrative pointing out it is wrong causes them to be more annoyed by the correction than the person who misled them in the first place.

Maybe I should stop.

You can hear the very small stones (large grains really) kick up from the tires through the vents and along the doors at low speeds only.

I hear them every day when I drive down my hill and I see them when I clean out the vents weekly so it’s definitely a thing but I’ve not seen even the slightest damage after 7000 miles.

whether the physics prevents it happening at speeds above 20mph or you just can’t hear it any more i couldn’t say but I don’t worry any more.

call me retro but I actually like this more old school approach to aero along with the manual charge port styling than the electronic wizardry. There is already so much hi tech stuff going on that a little old school race car aesthetic is a refreshing element.

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