Taking a curve in neutral ?
 

Looong ago when I was learning to drive (and there were not automatics) someone older than me told me you should never take a turn in neutral, the car would not handle well... It's something I'd never do... but I recall it happening once by accident when I was having fun on a mountain road, old car, gear didn't go in at all and I tool a relatively fast corner in neutral...nothing special happened...

Now that decades have passed, and I understand circle of friction better and spent years on track, I'm still struggling with the concept that it may or may not be true... It's obviously not something you'd do on track since you always try to maximize time, nor on the road because you want either some engine braking or the option to accelerate... But say you are cornering at a speed near the tire limit (but not above), other than missing the weight transfer aspect F/R due to deceleration or acceleration (and the % of driving tire lateral grip lost to accelerating or braking) - does it make a different at all to the car handling if you are in gear or not when taking the turn ? The car sure feels less stable... can anyone explain why ?

I know when driving my 911 I feel better when I am in gear. If I can apply power to come out of a corner it is more fun, and I can control how much power. And never shift gears in a hard corner.

There is an off ramp the I take to get my area of town that has a large fun sweeper and comes to a traffic light where I turn right. I have to come to a stop 80% of the time. I enter the off ramp at 70, and usually just kick it into neutral and coast to a stop. I am still rolling at a decent speed as I hit the curve, but I know the corner very well after taking it for 15 years. Since I will be stopping, or at least slowing to 15 MPH I just let the speed bleed off.

On the street I never corner very hard, lots of unknowns are out there. I learned that lesson long ago (1970s) when turning through a corner and all of a sudden I smelled diesel fuel, and I was sliding sideways towards a tall curb. I made the corner with inches to spare. Evidently some semi dumped fuel from his fuel tank with a bad fuel cap right in the corner.

I can honestly say that I never saw a curve in a soap box derby race. Never.

The real reason I would not want to take a curve in neutral is not having the right foot connected to the driving wheels on demand coupled with the potential for a mash up when re-engaging that unbalances the car if poorly done.

Clicky arrow.

Taking a corner in neutral removes your ability to control weight transfer with your right foot. All you have left is braking, and going for the brakes mid corner transfers weight to the front tires to cause understeer. You can do it but I prefer to have full control of the car with my right foot so I'll keep a gear selected.

I taught my kids never to go through a curve in nuetral but not for some racing type lesson, but because it would take them longer to react to any type of situation if the clutch was in/not in gear. Same as going through an intersection.

Depends on what you are driving, what kinda curve, how you are taking it (at speed?), etc.

I recall when learning to drive in the 356 I tended to want to do that to avoid going too fast or to avoid shifting while turning etc, and I fondly recall dad yelling "keep yer foot on the gas in the corners damnit!"

It's just the car decelerating. Going at a slow or moderate speed it wouldn't make any difference.

But hard cornering it would be scary. The SC, for instance, would want to swap ends.

I agree instinctively it seems like a bad idea, that's not my point, and I understand the argument of having options to balance the car with the gas...

I'm just asking from a physics standpoint, what difference does it make (if any?) to the car's handling if you are taking a curve in neutral vs with engine in gear, coasting (if you like assume it's a slight downhill curve to keep speed constant, also assume not at the limit but quick enough that you'd wanna be in gear, and finally let's say a cayman to avoid rear engine arguments) ..

It sure feels "odd" and less stable if if happens and you ever missed a gear entering a corner... Is it, though ? from a tire/grip standpoint I can't explain why it would be worse or why the car would care at all assuming you are within the grip limits - if anything there would be lower demands from the driving tires, so more "circle of friction" % rubber available for lateral grip. Not at the limit (yet not slow), shouldn't it feel 100% similar and corner the same? Sure doesn't feel like that to me, feel terrible... Just wondering if we had physics gurus here ;-)

Any downhill unpowered racing would perform this all of the time.

I've coasted around corners, not as a regular practice, but it will work fine as long as you don't end up braking mid-corner. I wouldn't want to be going through at the edge of adhesion. but going around well below threshold speed is fine from a dynamics point of view.

neutral vs coasting in gear - coasting in gear will involve engine braking (and aero drag and friction drag) vs coasting in neutral which only has aero drag and friction drag which are likely far less than engine braking. From that point of view, I believe that coasting out of gear would produce better, more neutral (no pun intended) handling than coasting in gear.

I coasting out of gear, you'd not have any tires doing anything but steering/tracking. I'm not sure what the effect would be at the limit since I've never tried it remotely near the limit. I'm sure that turning the front wheels will scrub speed and initiate deceleration. I would assume that at least initially, most of that deceleration is going to be on the front tires. It seems like that would be especially bad at the limit with a rear or even mid-rear engined car. If you aren't used to that happening without the ability to dial things in with the gas pedal, it might be weird. I assume you could train yourself to take corners like that, there may be some alignment or suspension settings that you could adjust to work better in that situation. Or maybe the upset would be so short settling into deceleration due to tire scrub at both ends of the car that it wouldn't matter as long as your steering input was smooth enough.

All the comments here are good. Having the car in gear give you more control options. With almost any car, having the drive wheels provide at least a little bit of power seems to make the car more stable, particularly with a rear wheel drive car. And perhaps that has to do with how the geometry of alignments is set up.

I'll add one thing, which is sort of just a bit more detail on the above: Cars seem to dive just a tiny bit onto the outside front wheel, in a turn where no power is applied. Perhaps the car is slowing down when no power is applied (on a flat plane). It feels like a tiny bit of power is needed to avoid loading that outside front wheel.

And then there are 911s. As we know, power is absolutely needed for stable turning. If we find ourselves in a situation where we are worried about losing traction and going off the road, the LAST thing you want to do is lift. Lifting transfers weight off the rear axle. This lightens the rear axle; reducing traction, while centrifugal forces are trying to push that engine to the outside of the curve. In a "pucker" situation, we have no choice but to keep our foot on the gas.

I have nothing to add other than, on the advice on many other Land Cruiser owners, I put my LC into neutral going down hill all the time...I don't live in the Rockies but I coast into roundabouts (Yes!) all the time but always put it in D 100 yards or so out. It just feels better and more controlled.

I hope Captain Ahab has some insight.

Yep, there's always drag on a car from aero and/or due to tire deformation and whatever other factors are causing a car to slow down. When you turn the steering wheel, both front tires will deform and increase drag and deceleration, especially on those two tires, which will cause the car to rotate. Presumably, when the car rotates, the rear tires will also deform and some of the deceleration will be generated by the rear tires as well (although I would think still biased towards the front). I would think the fact that the rear tires are decoupled from the engine and having to provide accelerative forces from the engine would mean that the tires would be able to skew farther into the cornering portion of the friction circle.

It's trick we occasionally used on snow/ice in a front-wheel-drive car to momentarily interrupt the understeer. But only as a last ditch effort to keep from going off road/track.

why would you?

there are a half dozen, easy, small reasons to not, why would you?

We're all wrong!

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That all too human trait that has both led to great innovation and utter disaster--curiosity.

I don't think Deschodt wants to coast around corners. I think a lot of folks that drive, especially manual transmission cars probably do because they have never been told not to and thought it was simpler at some point. And for most of the world that probably drives at 1-3 tenths all of the time, it probably doesn't impact them much at all.

The visitor's center at Paradise is the highest one can drive a car on Mt. Rainier.
Quite the curvy road snaking its way to the top.

Since a Porsche 921E has no power steering or brakes, I once shut the engine off when leaving the Paradise parking lot.

14 miles.

Coasting downhill, keeping as much momentum as possible around the dozens of curves allowed me to go 14 miles before needing help from the mighty sewing machine engine in the back for motivation.
For those familiar, I was able to get to the Kautz Creek mud flow area before cranking over those four tiny pistons.

At no time did I wish I was in gear.
Of course, this was for fun, and the experience I've had on the track no doubt helped.

Nothing different than floating the throttle to a neutral point.

My Jaguar has a shifter layout where it is very easy to go to neutral despite it being an automatic. There are situations where I go to neutral to conserve fuel where the level of engine breaking would be undesirable.

I do the same with a manual car.
If for a short time, I use the clutch and stay in gear.
If for a long time I want to unweight the clutch and go to neutral. (higher wear on thrust bearing to have clutch pedal in.)

Most cars have a front brake bias designed around dry weather driving.
This means the fronts are going to lose it under braking in the rain much sooner.
In a FWD car one could go to neutral in the rain under braking.
Or even stay in gear and go light throttle, but that is best not practiced in situ.

There are situations in an auto where the it downshifting could upset the rear of the car in such a situation if on the limit.

I've had a heavy duty pickup with rock as the rear spring rate do that to me on a curly interstate ramp in the wet.
Que up eurobeat from Initial D.

I still wouldn't pick neutral for that, I'd pick to float the throttle.

I wouldn't, please re-read a tad slower ;-) I'm just questioning the "common wisdom" that it's a terrible thing when, after it happened to me by accident, it made *no difference at all* to the cornering. And I could not explain to myself why it would be so bad from a pure physics standpoint, based on what I know of tires/handling/circle of friction.. (aside of added controllability of the weight transfer you get from the gas pedal )

Just a simple physics question, looks like having the car on either side of coasting (slight power, slight decel) changes nothing in this case. In no way would I recommend driving like that, controlling the car on the gas is a great option to have.

Common wisdom is worth understanding sometimes... The first year I owned a 911, I was terrified of even getting off the gas (let alone brushing the brakes) in any turn situation, even at low speeds, because I'd read so much about them spinning backwards. Track days quickly disabused me of that notion and established the SC as an understeering pig, that would only spin if you completely screwed up or reacted by surprise at the limit. You actually drive these fast with the gas pedal/brakes more than with the steering wheel, so it's worth digging into common wisdom sometimes !

Yep. I was also a bit scared about lifting in corners. I started slowly probing, first at low speeds, by backing off the throttle and lightly hitting the brakes. But at low speeds it's not much of an issue because the grip from the rear is so high. Then I started at higher speeds, nearer the limits, by modulating the throttle. That's where I really noticed the ability to steer. I also tinkered with getting into the gas in corners to initiate more understeer. It was very cool. One one occasion, I was a bit crazy in a 270º on-ramp. I went in at ~60mph, right as I turned the wheel, I reverse-blipped the throttle, let completely off and then got right back into it. It was pretty cool, I drifted around about half of the on ramp. I had a few occasions over the years that I was driving where I went into a corner hot and had to reduce speed.

What really surprised me was that when I sold the 911 and bought a miata, the miata was about as easy to steer with the throttle as the 911. On at least one occasion, I had the miata catch me off guard and step way out because I'd let off in a corner. The main difference was that it caught itself since it didn't have the lump in the back like the 911.

The only time I recall cornering in neutral was with an automatic transmission, rwd vehicle, downhill on snowy streets. The small amount of drive on the rears would be enough to promote serious understeer, so I learned to pop them into neutral under those unique circumstances.

Best
Les

It's a thing, racing/coasting Motorcycles down mountain curves with no engine assist.
Helps develop brake sensitivity and conserve momentum.

And my car trailer is always coasting and it does fine.

Should never free wheel in a turn because it kills the balance.
getting through turns at speed is all about shifting weight

shouldn't brake in turns either same reason

you want weight off your non steering wheels and on your rear wheels.

Weight off fronts prevents your turned wheel on the outsidfe from being jammed under the weight while it's rotating in different direction then the car is moving, resulting in skid
Weight on the rear prevents rear from coming loose

Brake before entry : All weight transfers forward Good for braking, bad for steering
reapply minimal power in the turn . Car goes to more neutral balance
build up power as your grip allows to power out All weight transfers to the rear bad for steering great for grip on rear wheels and power delivery (and why FWD sucks balls)

there is a track i go to that has a long sweeping curve out of a sharper one.
so i am excelling very hard but i also have to shift in the middle of the curve.
i was uneasy about it at first but all was fine,

i also have a circle track friend that is very good. i was telling him about getting sides in the 930 several times. he said, if you get into trouble just push the clutch in.

that takes all the weight distribution out caused by being on the gas or off the gas and the car goes "neutral"

It feels different because you’re used to having the car in gear and you can feel the difference in the forces that are operating on the vehicle and it feels unusual to you.

It really doesn’t matter because all cars understeer as designed by the factory and that tendency is not going to change. Removing longitudinal forces from the rear tires only gives them more capacity to grip in the lateral direction.

Clearly you understand the principles. :)

Trail braking is a thing and can help during track in, but always to throttle before apex.
On the track we turn them with the pedals as much as the steering wheel.

Turning a corner is an acceleration.

Braking is an acceleration. (negative acceleration)

doing the maths...

No doubt, no argument, on track trying to go fast, stay in gear. On the streets, with traffic of other idiots on the road, coming to a red light soon, in gear or not should make zero difference at 30 to 50% cornering ability.

I never use neutral on a straight or a corner. :)
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Really? Reduced weight on the steering wheels means reduced traction and understeer. It's the same reason why accelerating out of a corner results in understeer. So accelerating out of the corner removes weight from the front wheels and makes them not steer as well. Braking and putting weight on the front wheels makes them turn better because they have more traction (It also increases the size of the circle of friction, but reduces rear traction because that weight had to come from somewhere, which could result in a spin). So if you could balance the front/rear weight, you should have more balanced f/r traction and have reasonable turn in with less risk of a rear slide.
Yes, weight on the rear increases traction which reduces the possibility oversteer, but increases understeer.
It's good for steering, actually, great for steering because it increases the size of the circle of friction and allows for better turn in as long as you don't over power the fronts.
which would be the most similar balance to coasting in neutral
You contradict yourself a couple of times in your post.

I was going to point out that half of what he said made no sense but I don’t have time to get into that discussion. Thanks for doing the rest of us a favor.

me too:rolleyes:

mine.
stock cars are great track cars.
cheap, full roll cages, cheap motors.
mine has a quick change rear end so i can gear it for the track i am at.


couldnt upload it

in my youth I did something dumb. well, one of my dumb things.

I was going down a twisty road.
In my moment of brillance I decided to coast down. I pushed in the clutch, and put the car in neutral. WEEEEEEEEEEE!! FUUUUUUNNNNNN! it took very little time to build up some speed. I almost lost it going around a corner immediately. okay, let's stop this stupidity. I put it back into the appropriate gear and motored down the road. Glistening from a fresh sheen of sweat.

I would never corner in neutral ever again. in a 911SC that would have been potentially catastrophic. no bueno. maybe a slow-ass corner, like into a parking space.

this is incorrect.

proper, fast, braking will including braking while entering the corner.

this is also incorrect.

if you are on the power before the apex, you've run too late of an apex line, and over slowed.

proper throttle application is at the apex. this will also help you learn how much of a late apex you should be taking. on the power before the apex = too late. on the power after the apex = too early.

I always used both the gas and brake to get the back end to swing out to rotate the car. Gas keeps the front wheels turning some so the brake balance is shifted rear wards.