Understeer and Oversteer
Discussion
Lotusacbc said:
Just wondering, because I get these confused alot, but is Understeer when the car wont turn in as much as it can through a corner and Oversteer when a car turns too much into a corner?
Hi,
Close but not exactly. Understeer means that the car turns less than you've directed it to with the steering wheel and oversteer means that the car turns in more than you've directed.
There are a variety of factors contributing to this among them tire size, rear suspension set-up, camber and toe-in as well as the power being put down. Hope this helps. Happy Motoring!...Jim'85TE
lotusguy said:
Just wondering, because I get these confused alot, but is Understeer when the car wont turn in as much as it can through a corner and Oversteer when a car turns too much into a corner?
Hi,
Close but not exactly. Understeer means that the car turns less than you've directed it to with the steering wheel and oversteer means that the car turns in more than you've directed.
There are a variety of factors contributing to this among them tire size, rear suspension set-up, camber and toe-in as well as the power being put down. Hope this helps. Happy Motoring!...Jim'85TE
I see, so what I said it essentially right except that it pertains to the position or feel of the wheel. In other words it could cause an illusion because with understeer I might have the wheel turned alot but still not be in the turn where I like even the though the wheel says that I might? Even if I did not explain this right just now I know what you mean.
Lotusguy said:
....There are a variety of factors contributing to this among them tire size, rear suspension set-up, camber and toe-in as well as the power being put down. Hope this helps. Happy Motoring!...Jim'85TE
Hi Jim.. do you know if anyone has played around with the geometry of an S3 TE? I am curious if anyone has managed to make improvements.
From what I can see lotus got it pretty much right. I suppose it comes down to individual driving style and preferences. It would be fun to try a few small adjustments and test them out. Jan
>> Edited by F1Karting on Tuesday 20th January 03:40
All down to physics
If a car is travelling in a forward direction it will generally stay there until a force acts on it. Of which in a simple model of a rear wheel drive care there are two.
A – you turn the front wheels
B – you add power to the rear wheels
In A if you were to free wheel round a bend dependent on your speed you would induce differerent degrees of ‘under steer’ – the front wheels are braking away and beginning to slide. The position of the steering wheel is at full lock but the car is not responding – it’s under steering.
Classic over cooking a corner and you run out of road as the car ploughs on in a straight line – the energy in the cars weight is too much for the grip of the front wheels to cope with. Your next stop is the first solid object you meet.
B – Instead of freewheeling round the bend you add a healthy amount of throttle (gas) this induces the rear wheels to step out but still push the car in the direction of the bend as this happens you let off the lock on the steering wheel as the car is over steering.
Classic spin only this time you don’t see the first solid object you hit.
Balance them both and you lay rubber on the bend and pull off a smoking power slide that will have small boys wanting autographs, girls offering sexual services and you realising that you are cooler than an Eskimos nuts.
Enjoy
G
If a car is travelling in a forward direction it will generally stay there until a force acts on it. Of which in a simple model of a rear wheel drive care there are two.
A – you turn the front wheels
B – you add power to the rear wheels
In A if you were to free wheel round a bend dependent on your speed you would induce differerent degrees of ‘under steer’ – the front wheels are braking away and beginning to slide. The position of the steering wheel is at full lock but the car is not responding – it’s under steering.
Classic over cooking a corner and you run out of road as the car ploughs on in a straight line – the energy in the cars weight is too much for the grip of the front wheels to cope with. Your next stop is the first solid object you meet.
B – Instead of freewheeling round the bend you add a healthy amount of throttle (gas) this induces the rear wheels to step out but still push the car in the direction of the bend as this happens you let off the lock on the steering wheel as the car is over steering.
Classic spin only this time you don’t see the first solid object you hit.
Balance them both and you lay rubber on the bend and pull off a smoking power slide that will have small boys wanting autographs, girls offering sexual services and you realising that you are cooler than an Eskimos nuts.
Enjoy
G
fair explanation of overdoing it into a corner, and you get the idea of the difference in Over vs Under steer. for sure if you blast into a corner and crank the wheel the front wheel are first gonna slide and the who know the whole thins will be totally unbalanced.. this is not performance driving this is just crashing...
But to really evaluate the balance of the car, you need to drive in a steady circle ( skidpad) and drive at a constant radius (big circle) then gradually increase speed. the front wheels are barely turned and you are taking a smight curve
as you increase speed the lateral forces increase and there approaches 1g of sideways push on the car.
here we find out how the car really behaves.
as you sideways load the car by driving faster and faster in a circle, eventually either the front or rear tires are going to slip. at a certain sleed you will not beable to stay on course no matter how much steering or throtle input you use.
this is the cornering limit and if the front tires give way first then it is understeer, if it is the rears then over steer and if you just drift wide equally, it is neutral.
for sure in any car, if you lift the trhottle suddenly weight will transfer to the front and provide more grip, and the rear will swing out.
heavyy throtle, on a RWD will do the same, and oversteer. FWD may understeer if you gun it at the limit.
ok enough typing for now
But to really evaluate the balance of the car, you need to drive in a steady circle ( skidpad) and drive at a constant radius (big circle) then gradually increase speed. the front wheels are barely turned and you are taking a smight curve
as you increase speed the lateral forces increase and there approaches 1g of sideways push on the car.
here we find out how the car really behaves.
as you sideways load the car by driving faster and faster in a circle, eventually either the front or rear tires are going to slip. at a certain sleed you will not beable to stay on course no matter how much steering or throtle input you use.
this is the cornering limit and if the front tires give way first then it is understeer, if it is the rears then over steer and if you just drift wide equally, it is neutral.
for sure in any car, if you lift the trhottle suddenly weight will transfer to the front and provide more grip, and the rear will swing out.
heavyy throtle, on a RWD will do the same, and oversteer. FWD may understeer if you gun it at the limit.
ok enough typing for now
greenv8s said:
There's a much easier way to tell them apart:
Oversteer scares the passenger. Understeer scares the driver!
...or the other famous way to explain it:
Understeer- you crash the front end of the car into the wall first.
Oversteer-- you crash the rear end of the car into the wall first.
KFM
All depends on the driver. Lotus made the S1 Elise with slight oversteer (correct me if I'm wrong). When they brought out the S2 they made it with slight understeer because the average driver (including most women, no offence) are more comfortable with understeer in their Elises (with the exception the Sport 135 which has fatter front tyres and slightly different geometry for intended balance/oversteer).
For reference see the episode of Top Gear when Gavan Kershaw has to flick the front end into the corner to MAKE the car oversteer because it will tend to understeer naturally. Clarkson then says how do you do it? Kershaw says it is to do with the tyres and suspension and if a customer wants the Elise to OVER steer, they can widen the front tyres and adjust the suspension accordingly.
Oversteer usually makes people uncomfortable about the back end coming loose but understeer you just ease off the gas and the front end will eventually come back in the direction of intended travel.
Something like that anyway...........
For reference see the episode of Top Gear when Gavan Kershaw has to flick the front end into the corner to MAKE the car oversteer because it will tend to understeer naturally. Clarkson then says how do you do it? Kershaw says it is to do with the tyres and suspension and if a customer wants the Elise to OVER steer, they can widen the front tyres and adjust the suspension accordingly.
Oversteer usually makes people uncomfortable about the back end coming loose but understeer you just ease off the gas and the front end will eventually come back in the direction of intended travel.
Something like that anyway...........
Lotusacbc said:
So between understeer and oversteer, which is more usable and which would you rather have. I am guessing oversteer yes?
Depends how good a driver you are. If you need to be asking the difference, you want understeer, preferably supported by ABS and ASC!
More seriously, in a rear wheel drive car what you really ought to be aiming for is neutral steering, so that if you feed in more throttle it will *gently* progress toward oversteer, and if you lift slightly it will tighten the line.
What you don't want is dramatic oversteer as shown by the photo posted above, or dramatic understeer, where the front end washes out completely and the car just ploughs on in a straight line. The former is fun, but not the fastest way round a corner and sooner or later you will get it wrong and spin. The latter is both embarassing and slightly scary.
Yes the S1 was set up to over steer - which meant many people jumping in to it from a standard FWD car lost the back end frequently the commonest quote being 'my car is trying to kill me'.
The S2 is more balanced where you can provoke under or over steer at will - generally it’s better behaved - but will still bite you if you are not concentrating.
Personally prefer oversteer as its possible to recover in more adventurous situations.
If your car is going in a straight line even with the wheels turned you have less time and options for recovery than if the back end brakes free.
The S2 is more balanced where you can provoke under or over steer at will - generally it’s better behaved - but will still bite you if you are not concentrating.
Personally prefer oversteer as its possible to recover in more adventurous situations.
If your car is going in a straight line even with the wheels turned you have less time and options for recovery than if the back end brakes free.
Remember that experiment on elasticity you did with a rubber band at school?
No!
Well easy enough to replicate take a rubber/elastic band and stretch it until it snaps just before it snaps you will notice it stops stretching.
Why am I talking about elastic?
The same principle applies to cars & bikes.
All cars slide when taking a bend - faster you go the more it slides - until you reach the limit of elasticity of the grip between road and rubber and you fall off the road.
The skill is in the ‘balance’ of keeping the car on the road going in the direction you want be it using under or over steer.
The fast way is to get a 4 wheel drift so the car slides through the corner all wheels sliding equally – the slow but impressive way is the power slide back wheels hanging out opposite lock on – looks fun but very slow.
It’s this skill that separates us mortals from the people who get paid lots of cash to do the things we have to pay lots of cash for.
This can also work very well on saving your brakes. Just setting the car to a slide into a corner (if you do it right) will scrub off massive amounts of speed and as the wheels are still turning give you control.
The Mini naturally tends to under steer but as its so short low and generally a cool car with good handling it is one of the easier cars to play with (and cheep to bend it back).
Keep it shiny side up!
No!
Well easy enough to replicate take a rubber/elastic band and stretch it until it snaps just before it snaps you will notice it stops stretching.
Why am I talking about elastic?
The same principle applies to cars & bikes.
All cars slide when taking a bend - faster you go the more it slides - until you reach the limit of elasticity of the grip between road and rubber and you fall off the road.
The skill is in the ‘balance’ of keeping the car on the road going in the direction you want be it using under or over steer.
The fast way is to get a 4 wheel drift so the car slides through the corner all wheels sliding equally – the slow but impressive way is the power slide back wheels hanging out opposite lock on – looks fun but very slow.
It’s this skill that separates us mortals from the people who get paid lots of cash to do the things we have to pay lots of cash for.
This can also work very well on saving your brakes. Just setting the car to a slide into a corner (if you do it right) will scrub off massive amounts of speed and as the wheels are still turning give you control.
The Mini naturally tends to under steer but as its so short low and generally a cool car with good handling it is one of the easier cars to play with (and cheep to bend it back).
Keep it shiny side up!
bher said:
A Mini cooper owner told me that when pushed at the limit his car will slide by the 4 wheels. And following him, I saw this. Is this a type of understeer of more a neutral car pushed too far?
Ben
This is a neutral car being pushed, though not necessarily too far. I have had Minis, Imps and old Elans ('60's RWD) that used to handle like this - absolutely predicatable and progressive. Great fun, and you don't have to be Micheal Schumacher to set up a four wheel drift on every clear roundabout or medium speed bend you come to.
Modern cars (including my current Elise) have much more grip, but are mcuh less progressive in the way they break away at the limit - mainly due to the characteristics of modern wide, low profile tyres.
Speeking about these terms, we come down to the behaviour of tyres.
Old tyres tend to have only moderate grip, but maintain a certain build-up of side force when being pushed over the limit.
Modern tyres with their low section profiles try profit of nearly all of their grip potential, which means that once outside their stable region, they have very little additional potential left. This is why modern cars (and the Elise is one of them) have enormous grip and high cornering speeds, but are very difficult to control when being pushed to the limit.
This is not so nice if you want to impress by powerslides, but very nice to show that BM or Porsche that they are not the kings of the road anymore...
Old tyres tend to have only moderate grip, but maintain a certain build-up of side force when being pushed over the limit.
Modern tyres with their low section profiles try profit of nearly all of their grip potential, which means that once outside their stable region, they have very little additional potential left. This is why modern cars (and the Elise is one of them) have enormous grip and high cornering speeds, but are very difficult to control when being pushed to the limit.
This is not so nice if you want to impress by powerslides, but very nice to show that BM or Porsche that they are not the kings of the road anymore...
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