Talk:Lift-off oversteer

Requested rename

"Lift-off oversteer" gets around 10k google hits, while "drop throttle oversteer" and "trailing-throttle oversteer" get around 1k google hits each. I'm not an expert, but I've heard "lift-off oversteer" more often as well. Might it make sense to rename the article to "lift-off oversteer"? --Interiot 04:52, 29 March 2006 (UTC)

Ahh, it can be refered to as "lift-throttle oversteer" as well, which also gets 1k hits. Anyway, I've moved it to "lift-off oversteer". --Interiot 23:28, 17 April 2006 (UTC)

Snap-oversteer gets 20k google hits. I've setup a redirect, but it's something that we might want to think about in the future. Morwan 03:32, 2 December 2006 (UTC)

Isn't that like the new "drifting" the "cars" are now into, especially the rear engine foreign type as mentioned in the definition? Ttwould 20:39, 3 August 2006 (UTC)

While the vehicles once referred to by PJ O'Rourke as "ass-engined Nazi slot cars" were probably the most notorious for this, these days it seems to be more common in front-engined FWD vehicles, especially certain French hot hatchbacks. Mr Larrington (talk) 14:35, 26 August 2011 (UTC)

Physics

I'm not a physicist or car expert, but I believe the operative principle is not the decrease of contact patch size, but the reduce of normal force. Classical friction is based on coefficient between surfaces and force between them. The force between them is based on the normal force, which counteracts the weight of the car. As the car's weight transfers forward, less downward force is applied to the rear wheels, so the road pushes back with less normal force, so there is less force between the tire and road, so there is less friction. The size of the contact patch is unimportant - the same force of friction applies.

However, classical physics is often oversimplified. I'm sure there are much more important issues, such as deformation of the tire and the characteristics of the rubber.

Anyone who knows the physics of cars, please contribute! jauricchio 17:26, 1 September 2006 (UTC)

I am a physicist and racing driver and have replied below listing the errors in this article. It needs a complete re-write. 213.18.166.213 (talk) 11:38, 2 April 2023 (UTC)

You are correct, sort of. If you look into the reason as to why the static friction available increases with increased force perpendicular to the planes, it is because the contact patch 'grows'. The idea is that with, say 100 kg, 20% of the atoms in a tire (for instance) will be touching the ground. 200 kg, and the next 20% of the atoms touch. The increased force increases the contact patch (even if you cannot see it with the naked eye) and this increases the static friction. An interesting effect this gives rise to, is that, if you go over a certain amount of force, you will stop gaining traction. In our example 500kgs of force will have 100% of the atoms touching, so 600kg will not add any traction past 500.

Off course, I don't remember where I learned that, and there is a very good chance it wasn't from university or any other educational institute. So its not bible. Nereth 11:36, 16 June 2007 (UTC)

Gobledegook. Jackhammer111 (talk) 19:10, 21 August 2021 (UTC)

As another physics based question, from the same guy that posted the above answer:

I don't understand this: 'This decrease in vertical load causes a decrease in the lateral force generated by the rear axle, so the axle starts to accelerate towards the outside of the turn.'

I can understand that the decrease in vertical load will decrease traction available, but whats that about lateral force? Decreasing the vertical load by coming off the throttle cant, as far as I know, cause the tire to break out of static friction, since the decrease in force transmitted to the tire to move the car FORWARD would be more than enough to counteract any loss of traction from weight transfer away from rear tires. Am I thinking about this wrong? Someone help me out :/ Nereth 11:39, 16 June 2007 (UTC)

It's about weight bias. Lift the throttle and weight goes forwards, less weight on the rear makes it easier for the rear tires to slide. In racing, you lift if you are understeering to get the front to grip and as the rear starts to come around you get back to the throttle and power off the turn. It's great on gravel or dirt but it's done in sports car racing too.

but I have to say there is not enough documentation on this page to even justify its existence. It has one reference, Belknap pg 46, and who knows what that is. This is a Wikipedia vanity/opinion piece. It goes against all that Wikipedia is supposed to stand for. Jackhammer111 (talk) 19:10, 21 August 2021 (UTC)

The article is correct and sensible. Think about how tires work. see Tire load sensitivity. You seem fixated on static friction. That is not very helpful in this context. Greglocock 22:46, 16 June 2007 (UTC)

The article is not correct. I have described the errors below in my post. 213.18.166.213 (talk) 11:36, 2 April 2023 (UTC)

OR tag

Please discuss the OR tag here, otherwise I will remove it in two weeks. Greg Locock (talk) 21:58, 2 January 2008 (UTC)

The section lacks references to the origin of the test data and the analysis. If the origin is the editor, it is Original Research. --rxnd ( t | € | c ) 07:50, 3 January 2008 (UTC)

Yup, I made a digitalised image of a model of the phenomenon being discussed. OR? How would removing it improve the article? No unusual conclusions are being drawn from the graphs. Greg Locock (talk) 09:30, 3 January 2008 (UTC)

Per definition it is then OR. I agree in that the section and the image does add to the article. Nevertheless, Wikipedia cannot be a primary source. You are citing yourself. --rxnd ( t | € | c ) 11:37, 3 January 2008 (UTC)

There is no citation involved. This is an illustration for explanatory purposes, not research. Following your logic no photos (digital images) taken by an article's editor are allowed in an article? see Geelong and its talk page where we take digital images of the subject and include them in the article. Greg Locock (talk) 11:48, 3 January 2008 (UTC)

The graphs are generated based on an experiement, the photos of Geelong are not. Not citing yourself although it is your original material does not make it less original. Nevertheless, seeing that the image and analysis is of use, I will not push this issue too far. If you strongly feel that this is not a primary source and that there is no way to replace it with a secondary source, I see no problem with removing the OR tag. --rxnd ( t | € | c ) 13:00, 3 January 2008 (UTC)

I've checked 2 books about vehicle dynamics. Neither have much discussion of lift off oversteer, although Milliken does mention it in the tuning guide p397. I'm glad you don't want to push it as there doesn't seem much point. As to experiments... philosophically speaking would a video of a car undergoing this test be OK? I think so. Would the video be OK if it had a g meter reading superimposed? yes? So why does a computer model of the same thing count as OR? Greg Locock (talk) 20:31, 3 January 2008 (UTC)

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So far as I know

Virtually any car will exhibit L_O S in the right circumstances, if it doesn't have ESC (or even if it does in some cases). So there's not much point in peacocking about cars that do it or stopped doing it, in general. The Lexus is an unusual and notable exception.Greglocock (talk) 06:41, 28 December 2017 (UTC)

Recovery instructions are incorrect

Whoever added the current recovery instructions failed to consider recovery methods for RWD vehicles. I worry that people will read this article and take it as fact for how to save their car from a spin without realizing that it doesn't apply to their platform. I'm not knowledgable enough to speak to whether the method listed applies to 4WD/AWD vehicles, but it's nearly the opposite of what should be done in a RWD vehicle. Additionally, there is no linked source for the false information. — Preceding unsigned comment added by Gzideck (talk • contribs) 03:52, 8 February 2021 (UTC)

Are you saying you'd steer into the spin? I've only been driving powerful rear wheel drive cars on gravel roads for 30 years, apparently I have something to learn. Greglocock (talk) 07:20, 8 February 2021 (UTC)

Errors on this page

1. "Snap oversteer" is not a synonym for lift-off oversteer. Snap oversteer, as the name suggests is just sudden oversteer, and can be caused by a range of things, not just lifting off. For example, it's a common effect when on the power from low speed in a rear drive car with a limited slip differential with an aggressive setup - both driven wheels suddenly lock and deliver wheelspin to both rear wheels. It can be caused by bump steer too in a car with worn or poorly set up suspension.

2. Lift-off oversteer is not chiefly on rear drive cars (first sentence). As is correctly stated later in the intro, it occurs from "weight/load transfer". This is therefore independent of the driven wheels. It was an infamous handling trait of many front wheel drive hatches, like the 205 GTi. With rear drive cars you do get engine braking at the rear wheels only, adding to the effect, but this is a fairly minor effect and isn't even mentioned in this article. I think the misunderstanding might come from the fact that rear drive cars are more likely to be driver's cars with neutral setups, so more easily affected by changes in balance (by design - this is what makes a car good to drive - it responds).

3. Recovery: Yes, this is the effect, but I believe it's dangerous advice and the wrong way to think about it. Better advice is to keep the steering pointed where you want to go. The inevitable result of "steering the opposite way" is to over-correct and smash into the outside barrier. You Tube has literally thousands of accidents like this, in fact it's probably the most common sort of accident on track. I don't even need to provide links as evidence, just watch some crash videos on You Tube and you'll see that most of them are caused by lift-off oversteer followed by over-correction. What happens just before the lift off oversteer? Well, it's actually understeer, which leads me to point 4:

4. Lift-off oversteer is actually more of a steering problem than an inevitability from poor throttle control. It is actually possible to back off completely in the middle of a corner in any car without oversteer, if you're steering correctly. I've demonstrated this in several cars known for lift-off oversteer and had no oversteer at all. Several race tracks actually require this, lap after lap, even braking mid-corner. Look at Snetterton, in the UK, for example: there are two corners that have braking zones that start in the middle of the previous corner. The trick is to use an appropriate amount of steering lock. Most lift-off oversteer moments are not caused by weight transfer alone, they are caused by the front wheels having too much steering lock on, and when the force comes back down on them, this lock is realised, pulling the front of the car towards the inside of the corner. The rear is lightly loaded, and the two combined to create oversteer. Too much lock is a driver error as a response to understeer. The other response to understeer is to back off. Combine the two, and around you go. If a driver always points the steering where they want the car to go, they will never experience lift-off oversteer.

Creds: Physics grad with an interest in car dynamics, amateur racing driver of 22 years (FWD, RWD, ME, FE and RE), former racing instructor, and keen sim-racer. RobManser (talk) 10:44, 31 March 2023 (UTC)

Sadly anecdotes aren't much use for wiki articles. i agree with much of what you say, and have removed the more egregious errors. cred vehicle dynamics engineer. Greglocock (talk) 23:55, 2 April 2023 (UTC)