Is all wheel drive really worth it in supercars?

[Ciro Pabón]

In a racing situation, yes. Marginally.

However, the AWD car would start better and overtake everybody but in the end it would be overtaken by all RWD cars having less weight and less transmission losses.

Panacea

First, AWD is usually sold as a panacea, a cure-it-all

(DISCLAIMER: this post may be a long and boring one, but at least you can use the word "panacea" today).

The message is "Buy our AWD car! It will help you to dodge Bambi!".

Will you kill Bambi, that magnificent creature? (notice the evil, anti-4WD advocate Tim Wright in the back, in his superhero costume, as usual)


Well, in truth, AWD wouldn't help Bambi that much. Starting with his father being killed by a gun, not a supercar, but I digress, as usual...

... and yes, that's not Tim, it might be Richard, in his mod costume... or perhaps Greg Locock. It's the Alzheimer, I think, but I forgot.

Shut-up-and-take-my-money car: Tesla autopilot, dual motor, AWD, 691 HP electric, 0 to 100 kph in 3.2 seconds... and it can dodge Bambi: if that's not modern, I don't know what is. A hipster in disguise?


Notice the used car seller talk in the previous video: "fastest car in the world in the category of cars-with-a-pink-roof-not-previously-owned-by-a-klingon! Zero to umpteen mph in 3.3423 seconds!"

Snake oil sellers would be proud: this guy has more words than you can hang in a fence...

However, the truth is that when it comes to handling, AWD is overrated (not to mention heavier and gas guzzling).

So, what's wrong with Jersey's Tom point of view besides disagreeing with me? (if he's wrong: I might be the one).

He says "all things being equal".

Yes, it's true that AWD will give you better acceleration (and that's why it's universal in rally racing, where you have to accelerate like mad after a 180 degrees curve on a dirt road, hardly a normal situation for a supercar).

On a side note, I helped to drive an 4WD to victory many years ago, in a local rally race and it was super nice.

This is the first AWD car... not the one I drove: I'm not that old, but not by much


The sad truth is that the law of physics imply that cornering ability depends on tyres and suspension. Once you get to the grip limit, that's it.

For one thing, AWD doesn't improve the handling and it doesn't improve stop distances, either, in case you're wondering why I prefer new snow tyres.

After all, AWD is better than FWD or RWD when you have more power than you can transmit to the ground and if a snowy road it's not that, nothing is.

Besides, AWD will make you confident.

(NOTE TO PEOPLE OF WARM CLIMATES: in my hard earned, paid with cash, experience, snow banks are NOT puffy and soft).

I'd rather have a Toyota on four new snow tyres than an Audi on all season tyres


And that's why I dare (hi, Tom! sorry! apologies! it's a joke! don't tell anyone, anyway!) to contradict Jersey Tom and side with lkocev.

If the budgets are equal, it's much better to invest in better tyres than in an AWD system.

Of course, I've never seen a "supercar" (what a horrible name!) in a racing situation, because racing cars and supercars are two different propositions.

However, as bill shoe could say, do not trust supercar owners. Let's imagine for a moment that you're going to risk a one hundred thousand dollar car by putting it in the hands of an overgrown brainless risk taker with the attitude of a five years old child (a.k.a. "a racing driver").

In that case, when you're racing and not showing off (which it's like the difference between Survivor and The Bachelor), what would you pick?

I would pick this one. Angie Layton, from Survivor (I wouldn't care about winning: I prefer to lose with a smile in my face)


Now, to tell the truth, if you have to choose between AWD and tyres, get the darn tyres.

Some people (fools!) disagree with me. They say that AWD improves oversteering. However, that's not improving handling but acceleration.

That's why it's so useful in rallies: there you don't really handle the car, let's be sincere, in rallies you just point the car in the general direction of the road, grind your teeth and hope for the best.

To be even more frank, I've tried (for a few magical moments) a new Audi with improved AWD and, yes, I know, the new AWD brakes the inner wheel and gives more force to the outer wheel.

Notice the clever use of the word "potential" when talking about wheel grip, right at the start of this (I think) interesting and pertinent video


It actually improves (in a minuscule amount) your handling. It costs a cartload of money, so there it evaporates the premise: all things equal, that's the basis of rationality.

Moreover, in racing it would be unjust: if a system like the one showed makes its way into F1 that'll would make Hamilton as good as Alonso...

... which takes me to the history of this things in F1, hoping it will be enlightening.

AWD in racing cars

Actually, a few cars have raced in F1 with AWD. The Ferguson P99 Climax was the first Formula One car to win with AWD and last car to win with a front engine.

End of an era but not the beginning of a new one: who else but Stirling Moss could win in an AWD car? Notice he drives LIKE A BOSS


Actually, this was a clever bet by Ferguson, that should remind us that mos threads in this forum, and most discussions in engineering have a very short answer: "it depends".

It is a Climax powered car, with a front engine by choice, even when Lotus and Cooper had recently demonstrated this was an inferior solution. Why?

Well, by putting the engine where you see it, the car has an almost perfect 50-50 rear and front weight distribution and the position of the gearbox makes the position of the engine a necessity. This makes this a very good car.

Actually (oh, c'mon, J Tom... don't nag me! ) Moss said this was his favorite car and this was a man that had won with legends lik the Mercedes W196, the Maserati 250F or the Cooper T51.

Few months later, FIA (sigh, as usual) decided to change the maximum weight of engines. This made the Ferguson an oddity: it was impossible to achieve balance with the new weight. So, goodbye frontal engine.

Then, a miracle happened. Strad would be proud of living in that era (but I'm afraid it's autogyro, marcush, xpensive and me the only ones that can remember it).

Yes, it's a Cosworth DFV, and yes, it's Mario Andretti, and yes, it's a Lotus, and yes, it's Nürburgring. Allow me a moment while I dry my eyes, the tears don't allow me to see this well


However, the racing gods are cruel. Remember Taraxippus?

Well, as things went then, 1968 was one of the wettest racing years in history. So, in 1969, with the light Cosworth engine many teams gave AWD a go. The result? Well, 1968 was one of the driest years in history. Taraxippus. So, AWD became an additional weight that gave no advantage but disadvantage. It depends, many times on luck, as Nico Rosberg knows.

Now, sometimes the gods take, but sometimes the gods give.

Enter Dave Walker, Zandvoort, 1971, in one of the weirdest cars that ever existed...

... to illuminate Strad's currently somber and boring F1 world.


Ok, it's a weird car by the looks and by having an AWD drive.

However, how many of you know that this car had no gearbox, a Prat and Whitney (ermahgerd!) turbine, has no clutch, the weird among weird Ferguson transmission?

Now, Dave Walker was no Emerson Fittipaldi (its first driver) and he qualified a lowly 22nd. Taraxippus, darn.

Then, the gates of heaven opened at Zandvoort and the weird car with the regular driver started to show what an AWD transmission is good for.

In the words of no one less than Colin Chapman: "that was the one race that should, and could, have been won by a four-wheel drive".

Unlike many contenders in 1969 that, curiously for a balanced AWD transmission broke many suspensions, Mr. Walker crashed after overtaking 10 cars in a hurry.

Finally, it was the Williams FW08D which made FIA ban AWD transmission in F1...

In the words of Patrick Head, it was banned because "someone in a FOCA meeting said it would drive up costs and cause chaos during pitstops".

... and you thought FIA was to blame for everything! C'mon, FOCA existed

Yes, it's Senna, and yes, it's Donnington Park, 1983 tests, and yes, it's a test for Williams, and yes, he broke the records of Laffite and Rosberg in his first attempt and yes, Williams could not break previous contracts, and yes, Senna could not sign for Williams, which was his dream, and yes, he ended in Toleman and the rest is history


Darn, I have to go to work, but as McArthur, I will be back to nag you with my short posts now that my brother finally is out of the hospital...

NOTE to Tim: c'mon, everybody says doble-u, doble-u, doble-u (nine syllables) instead of World Wide Web (three syllables)

[Tommy Cookers]

Where will the specific performance advantage come from? If the tires are equal, where is the extra lateral grip coming from?

There is no extra lateral grip. The performance increase comes from having extra longitudinal traction. Its using longitudinal grip at is available on the front tyres but is not used in a RWD car.
The advantage of AWD is that you have more longitudinal acceleration at the exit of every traction limited corner. Then after you leave the traction limited region you have a positive speed delta compared to a 2WD car and this means you pull away from the 2WD car all the way down the next straight even if you both have the same power.
Its a huge advantage and also the reason why AWD cars are ballasted more in the series where they are allowed.

on this basis AWD is a large benefit to a front-engined front drive base car ('weight 'distribution 60/40 at max acceleration)
eg the Quattro case
and little benefit to a mid-engined rear drive (ie supercar) 'base' car ('weight' distribution 35/65, even 30/70 at max acceleration)
best acceleration at the exit of traction limited corners having been the prime reason for the move to mid-engines

this benefit is greater on slippery surfaces ie more traction limiting (and arriving at the next corner faster is a problem ?)

[Tim.Wright]

True its more of an improvement for front engined FWD cars, but even for a mid engined car the gains are huge.

If you have a load distribution of say 30:70% under acceleration in a RWD car, then there is circa 50% of extra grip available on the front axle that is not being used.

[autogyro]

Ciro forgot to add a very basis point.
Sure you can buy a super car with better tyres to better AWD.

If you are driving on ice however and you want to stop quicker buy one with less weight.
I would much rather have my TWD Golf than any heavy FWD or AWD monster.

[lkocev]

True its more of an improvement for front engined FWD cars, but even for a mid engined car the gains are huge.

If you have a load distribution of say 30:70% under acceleration in a RWD car, then there is circa 50% of extra grip available on the front axle that is not being used.

Tim I see your being a little bit generous with your approximation, which is OK but your still assuming that all else will be equal. You won't end up with 50% increased acceleration rate because some of that grip that you write of will be offset by the extra mass of the AWD components.

'You can't have your finger in the pie and hand in the cookie jar at the same time' ...

I'll quote some details from current generation Porsche 911 (991) models, since you guys seem to be arguing that the advantage is in acceleration.

911 Carrera (Base)
Power: 257 kW
Mass(unladen): 1380 kg
Tires(front-rear): 235 - 285
0-100 km/h: 4.8 s

911 Carrera 4 (Base)
Power: 257 kW
Mass(unladen): 1430 kg
Tires(front-rear): 235 - 285
0-100 km/h: 4.9 s

911 Carrera S (rear wheel drive)
Power: 294 kW
Mass(unladen): 1395 kg
Tires(front-rear): 245 - 295
0-100 km/h: 4.5 s

911 Carrera 4S
Power: 294 kW
Mass(unladen): 1445 kg
Tires(front-rear): 245 - 305
0-100 km/h: 4.5 s


The price difference between Carrera and Carrera 4 is almost £5k, between S and 4S just above £5k. Now I know these are not supercars, but the 911 is a sports car none the less. Neither of these AWD variants out performs the rear drive ones from 0-100km/h, the area where you guys claim the advantage exists. I might add that the S and 4S are not an equal comparison anyhow, because the 4S has wider rear tires, is anyone willing to quantify the traction advantage that gives?

And then we could get into the argument that the 911 is a compromised package for rear drive application because it is designed with the provision to have an AWD system fitted. So how can anyone expect that we will ever achieve 'all else being equal' ?

I only see an advantage in that an AWD car would likely be more forgiving to drive. Give too much throttle through a turn and a 4 wheel power slide is likely less intimidating to regain control. Hell you likely wouldn't even need to give the steering opposite lock. Do that in a rear drive car and good luck catching your rear before it overtakes the nose. Outside of that, its not going to improve the fundamental grip limit of a car.

[mrluke]

So we are now saying that there is 0 advantage of 4wd yet it dominates in every race series it isn't banned from.

[Blanchimont]

One point is that in a RWD car the rear tyres have to provide tractive force to accelerate the car's mass but also have to speed up the front tyres and overcome the rolling resistance at the front axle. In an AWD car the driveshafts make the four tyres spin and the tractive force can be used to accelerate only the car's mass. Of course only below the traction limit, but at the same time this is the place where most of the time is gained!

[autogyro]

Best drive train is rear electric prime, with part time electric front.
No modern super car should be without it.
The ICE should be nothing more than a range extender option until battery range increases.

[Blanchimont]

Some quick calculations for a 700kg car with a wheelbase of 3,4m and a CoG height of 0,25m. Tyre friction coefficient decreases from 1,6 at a normal load of 0N to 1,2 @ 5000N [1,6-0,4*(Fn/5000N)^2]. The graph shows the acceleration from a standing start, so no aero influence, for different weight distributions.

With different parameters and downforce at higher speeds the results can differ, of course.

[Andres125sx]

I´ve had the honour to give Ciro his 200 upvote, long post but very interesting, as usual. I liked your definition about racing drivers =D>



I see a problemm with this discussion, people is focusing on advantage-disadvantage of AWD cars on tracks, or in ideal conditions. But as someone pointed supercars are not racing cars, so they´re not used on ideal conditions.

Racing cars are tuned for any conditions, if it´s dry they use slicks, if it´s raining they use wet tires, height and suspensions are also dialed for each situation, roll bars, springs, differential/s... While supercars are supposed to be used on any condition, dry, wet, clean tarmac, dirty one, new tarmac, old and slippery one, even on roads with different types or with perfect tarmac wich suddenly becomes a slippery one because of sand, or an asphalt joint...

In these conditions, AWD is a huge advantage. We could say if you´re using your supercar to the limit on roads then you´re a criminal who should be arrested, but IMO supercars are more of a theoretical exercice, they´re about being the fastest car for usual roads, and for that purpose AWD is a must

Once you put slicks on it and go to the track on a sunny day probably a RWD car could be faster and it will be funnier for sure, but for road use both on sunny and rainy days, with new and used tarmac, with new and used tires, on slow corners with poor traction (even on dry conditions) you´ll find on every road you go.... AWD will be a huge advantage


Personally, I´d prefer a RWD car with a nice ESP you can connect or disconect to match your brain status, fully connected when I´m distracted, connected but not too intrusive when I feel sporty, disconnected for those days you feel like Loeb/Alonso I prefer a fun car than the fastest car on planet and a RWD is better for that purpose, and today with electronic aids it can be as safe as any other, but if you want the fastest car for road use, any road, and any condition, it should be AWD

[NoDivergence]

I´ve had the honour to give Ciro his 200 upvote, long post but very interesting, as usual. I liked your definition about racing drivers =D>



I see a problemm with this discussion, people is focusing on advantage-disadvantage of AWD cars on tracks, or in ideal conditions. But as someone pointed supercars are not racing cars, so they´re not used on ideal conditions.

Racing cars are tuned for any conditions, if it´s dry they use slicks, if it´s raining they use wet tires, height and suspensions are also dialed for each situation, roll bars, springs, differential/s... While supercars are supposed to be used on any condition, dry, wet, clean tarmac, dirty one, new tarmac, old and slippery one, even on roads with different types or with perfect tarmac wich suddenly becomes a slippery one because of sand, or an asphalt joint...

In these conditions, AWD is a huge advantage. We could say if you´re using your supercar to the limit on roads then you´re a criminal who should be arrested, but IMO supercars are more of a theoretical exercice, they´re about being the fastest car for usual roads, and for that purpose AWD is a must

Once you put slicks on it and go to the track on a sunny day probably a RWD car could be faster and it will be funnier for sure, but for road use both on sunny and rainy days, with new and used tarmac, with new and used tires, on slow corners with poor traction (even on dry conditions) you´ll find on every road you go.... AWD will be a huge advantage


Personally, I´d prefer a RWD car with a nice ESP you can connect or disconect to match your brain status, fully connected when I´m distracted, connected but not too intrusive when I feel sporty, disconnected for those days you feel like Loeb/Alonso I prefer a fun car than the fastest car on planet and a RWD is better for that purpose, and today with electronic aids it can be as safe as any other, but if you want the fastest car for road use, any road, and any condition, it should be AWD

Any road, any condition, yes AWD. But I personally wouldn't drive my supercar in the wet hard at all.

In the dry on decent tarmac, RWD with semi-active suspension, high downforce, and sticky tires any day over an understeering AWD car.