This actually happened when my dad asked me to try manipulating the throttle while he pushed; he accidentally left the car in drive, then got out. Funny, but my heart stopped for a second (car's nose was 3 feet from the concrete pier wall).


I will say there truly was no available traction. Advanced vectoring AWD systems like current gen 4matic or quattro might have helped by pulling the front end left and right, thereby repositioning the back end to grapple on undisturbed jagged ice, but once the driven tires spun a little, it was just incredibly slick with no bite. Kitty litter would have been a good thing to have; I never thought to keep any because the extra weight does affect handling.

It's a Nikon D800. I chose the 24mm f/1.4 to get the composition I was seeking.

 

I promised myself I wouldn't get involved, but you're so off-base that it's killing me.

Are you saying that he has no understanding of basic physics because you believe that doubling the contact area (more than doubling the traction considering the front wheels have more weight over them) would make 'little difference'? It makes quite the difference. Specifically, double or more. I'll be the first to say that you can still get stuck with 4Matic, and you can't brake any faster than a RWD, but in situations where you're looking for traction so that you don't become stuck in ice / snow - 4Matic makes a vast difference. I've driven both RWD and 4Matic - we own both. The RWD becomes nearly useless with a few inches of snow (on all seasons, because I don't find it worth swapping tires every winter) - it's all over the road. Our 4Matic works absolutely wonderfully and has never been stuck even in a foot of snow where the car is beginning to act like a plow. I believe you are the one in need of a physics lesson. Just to be clear, yes snow tires would be even better, and yes you could still get stuck on an icy hill with a 4matic -- but it's not nearly as common as with RWD.

 

acr ~ it's great to see you posting again.

 

Nice shots! Is this off of Sheridan Road in the Winnetka area?

 

Thanks Glyn, always a pleasure to see you around here.

 

Beautiful pictures. I love the Bi-Xenons on the W204, definitely makes the car look 100X better!

 

Thank you; it is.

They really do look sharp, and they perform beautifully.

 

Oh boy, I'm honored.
It does not. As soon as you have any slippage on ice, you are essentially polishing the surface under the tire and making it even smoother. With 4matic, if you start getting slippage, which you will when trying to move on ice, you will have 4 polished areas.

adanmtxt1 (the OP here, you know, the one actually involved in the situation here) hit the nail on the head - Thank you, but with 2 engineering degrees under my belt I think I'm more than well versed on the subject of Physics... certainly enough to be confident in what I'm saying here.

You are 100% correct though, that Kitty Litter or sand would have fixed this situation regardless.

 

MDMGguy , sometime it's better to remain silent and be thought a fool than to speak out and remove all doubt. Just let it go man.

 

Sometimes it's better to know what in the hell you are talking about prior to getting involved in a discussion than it is to get in one in which you have an incomplete knowledge of the subject at hand. At any rate, don't come on here and with less than 2 months under your belt try to get ****ty with an established member.

 

I bailed out of this thread, having become quite disappointed with the tone it took. From a technical viewpoint, MDMG is correct. Expressed mathematically,

x=coefficient of traction
2 or 4 = number of powered wheels


2x=0, where x= 0 on a low mu surface, below capability of all season tire to produce any traction.
4x=0, where x= 0 on a low mu surface, below capability of all season tire to produce any traction.

Therefore, on such a hypothetical surface,
2x=4x

However, if an improved traction tire is fitted, such as a hyrdophilic winter tire,

2x=2, where x = 1 (as assigned value of improved tire traction) on a low mu surface.
4x=4, where x=1

AWD with proper tires is the superior overall combination. But, the next best is two wheel drive with proper tires. Tires are the most critical limiting factor.

We don't know the exact characteristics of the surface the OP was on. From his description, it seemed close to below the capability of one, two, three, or four all-season tires to generate any traction. Variations from this post are all a matter of degree. However, the bottom line remains, if one has a rear wheel drive car, and can make one change to deal with poor traction, changing the tires produces far more benefit than adding two more spinning wheels of the original tires. Car and Driver has done this test more than once, with the same results.

I'm not going to debate with anyone, as I don't care for the style of discourse here. Have a good Polar Vortex.

 

 

I think the core result remains that my all-season-season tire-equipped rwd MB could not compensate for my poor (stupid?) decision that evening (!). I'll wait for the pier to dry off next time!

 

Good way to put it!

That said, throw some grit of some sort in the trunk. I have 2 50# bags of sand in my trunk for a little ballast right now, but in the event I get in over my head - one or both can be sacrificed to claw myself to better ground.

 

I'm trying to be reasonable here, and you do seem to be very knowledgeable, but I can promise you that our friend has absolutely no idea what he is talking about. You make the assumption in your proof above that the all season tires are producing ZERO traction. This is certainly not the case. They are producing traction, but not enough to overcome the force produced by the weight of the vehicle, so they're spinning in place.

If you say that a 4WD vehicle with proper tires is better than a RWD vehicle with them (and you did say that) then the same rule would apply to any tires that are producing any measurable amount of traction above 0. For arguments sake, let's say that the traction coefficient of the all seasons is 0.25 and that of the snow tires is 1.

2x=.5, where x = .25
4x=1, where x=.25

As I said much earlier, this is double the traction. This proof shows that you will double any traction that you have with AWD. Naturally you cannot double zero, but zero is physically impossible on Earth with any known substances (unless the vehicle is airborne, and even then you'll be getting wind resistance from spinning wheels) And naturally we are both dumbing this down since there are numerous other variables at play (most importantly, those two additional front wheels would have more weight over them in a car without a 50/50 weight ratio, further improving the gains). With proper tires, it would of course be much better. A vehicle with RWD and great snow tires could easily outperform an AWD vehicle running on all-seasons in many aspects. This could be easily plugged into our numbers above if we had the data for the different tire types. I simply prefer the year-round benefits of AWD over the chore of switching to snow tires every winter.

To reiterate, all I am saying, is that having 4 wheels delivering power is going to be better at transferring that power to the road on dry roads, wet roads, snow, or ice. How much better, is of course up for debate. Based on years of real world use, with crappy all-season tires, I'm quite certain there is a huge improvement - so much so that I wouldn't buy a car without AWD at this point, even if it never snowed here. I can floor it in a turn and merge beautifully in a pinch without losing control or activating any significant amount of ESP.

Edit:
One last angle I'd like to approach this from so that it's clear -

There is no known substance in which you can have truly zero traction (I use the word lightly, we can say coefficient of friction). If we knew of such a substance, we would be able to create a perpetual motion machine (for example, by creating a surface and a spinning top made of such a substance and spinning the top inside of a vacuum. It would never stop spinning. The same applies to this question of traction of the tire on ice. It has traction. It isn't enough traction to counter the weight of the car and move it, so the wheels spin in place. You add an additional two wheels to the drive train, and you have now effectively doubled the traction. This can be, and often is, enough to move the vehicle rather than spin all four wheels.

I am surprised that someone who claims to have 'multiple engineering degrees' doesn't comprehend such simple introductory college physics and would rather call names without even addressing the argument he attempts to make.

Court is adjourned.

 

We're talking about a situation with many unknown factors here, so I was not about to dive too deeply into it. Sportstick explained it very well, IMO, so I didn't feel that anything else needed to be said. I'm certainly not going to waste my time, energy or bandwidth arguing with you. I learned long ago that you are impossible to deal with when you *think* you are correct.

Furthermore, you know nothing of my background or education - so your attempted slam at my education is cute, but something I expected from you.

Your level of arrogance is astounding.

Congratulations, you have reached the milestone of being the second person I have use the ignore feature on here. I invite you to do the same.

 

Ok. I posted a factual argument, taking into account previously posted information and showing that it is being incorrectly applied. You simply post about how angry you are and refuse to apply any intelligence or logic to the discussion. Further, you do not address any of the facts that have been stated, you simply make excuses because you have no legitimate argument to make. You have been proven wrong on this topic.

Cars have brakes on all four wheels. Do you know why? Because it doubles the contact area with which the vehicle can apply stopping power. The exact same physics apply to doubling the drive wheels. You have no argument to make. It's dead in the water. If you are so certain that you are right, please remove the useless rear brakes from your vehicle.

Thank you for placing me on your ignore list. I very much doubt I'm only the second person, or maybe they were all smarter than me, and placed you on theirs first. I shall do the same to prevent any more of this useless arguing.

 

Can all of you just shut up about it already. Really, who honestly cares about the differences between all-wheel drive and two-wheel drive. They both have their positives and negatives. You both provided well enough evidence to support both claims.

This thread was supposed to be a nice photoshoot of a fellow MB owner's car, that happened to get stuck on a pier. Now it is just an argument lost in the middle of the woods. How about we go back on topic and congratulate the OP for the wonderful pictures he provided.

Now the court is adjourned.

 

Is your dad James Cromwell?

 

Agreed. It was a valid discussion until it got so out of control / silly.

 

Best if you all moved to a better climate