I don't understeer when I trail brake so this can't be right can it?
I don't understeer when I trail brake so this can't be right can it?
while i generally agree this definition would mean that ass out high angle drifting is a situation of perfectly normal neutral car behaviour which is an odd lable for drifting to say the least
thats the point you bloddy tommy
... the definition is ... lets say challengedYou've lost me completely
understeer is when you either fdrive fwd or just lose trackion/racing like and because of your cars momentum you can get out of the direction your driving ( thats the simple discription )
Yeah, I guess that only works in defining understeer from a neutral state.
ok once more
- like axus said for the car to turn you need a torque round/along the vertical axis
- to get that torque you need more lateral froce at the fron than at the rear
- to get more lateral at the front you steer in thus inreasing the slip angle at the front
by the standard definition the car would understeer every time you turn the wheel while driving straight
From the engineering point of view the slip angle difference definition is generally accepted. Another way to think of under/oversteer is to take the extreme limit view. If the car would drift out rear end first, it's oversteer and vice-versa.
For a driver, understeer is just a matter of the car not achieving the yaw rate and tightness of line he/she desires and vice-versa.
For a driver, understeer is just a matter of the car not achieving the yaw rate and tightness of line he/she desires and vice-versa.
Dictionary.com Unabridged (v 1.1)
un·der·steer
–noun
1. a handling characteristic of an automotive vehicle that causes it to turn less sharply than the driver intends because the front wheels slide to the outside of the turn before the rear wheels lose traction.
–verb (used without object)
2. (of an automotive vehicle) to undergo understeer, esp. excessively.
Compare oversteer.
[Origin: 1935–40; under- + steer]
American Heritage Dictionary
un·der·steer
intr.v. un·der·steered, un·der·steer·ing, un·der·steers
To turn less sharply than the operator would expect. Used of vehicles, especially automobiles.
n.
1. An instance of understeering.
2. A tendency to understeer.
un·der·steer
–noun
1. a handling characteristic of an automotive vehicle that causes it to turn less sharply than the driver intends because the front wheels slide to the outside of the turn before the rear wheels lose traction.
–verb (used without object)
2. (of an automotive vehicle) to undergo understeer, esp. excessively.
Compare oversteer.
[Origin: 1935–40; under- + steer]
American Heritage Dictionary
un·der·steer
intr.v. un·der·steered, un·der·steer·ing, un·der·steers
To turn less sharply than the operator would expect. Used of vehicles, especially automobiles.
n.
1. An instance of understeering.
2. A tendency to understeer.
This thread actually got me to start reading the handling parts of Milliken. Haven't gone far yet and it doesn't look like it's going to be easy but I did come across a quote that seems relevant to some of the confusion in this thread.
So as I understand it the race driver's sensation of understeer is not closely related to the engineering definition of front slip angle > rear slip angle. To really understand it I would need to get a bit more involved with the subject than I have time for ATM but at least you guys know where to look now (in case you didn't already).
So as I understand it the race driver's sensation of understeer is not closely related to the engineering definition of front slip angle > rear slip angle. To really understand it I would need to get a bit more involved with the subject than I have time for ATM but at least you guys know where to look now (in case you didn't already).
...you pillet, did you seriously just paste a non-technical definition of understeer from a dictionary where the OP wants a technical definition? I doubt there's a person on this forum that doesn't know what understeer "means", but we can't seem to find anyone that actually knows how to implicitly define when it's happening in engineering terms.
Google...yahoo?
Understeer IN MY OPINION has to do with steering and mostly the drivers opinion. Lose of grip on the front wheels is something different, related but different.
From my karting experience, understeer can be from, not enough front grip, too much rear grip, not enough weight transfer or a bind. So if I was going to explain understeer in a technical sense, I would have to go through nearly all the physics that are related to a car turning. I could recite tech info from some books, but I'm lazy...so heres some stuff I found online.
-Most explain understeer as a technical term...which I don't 100% agree with, but thats what you say he wants.
You can talk about a cars technical specifications in order to explain why a certain car or situation would be more prone to understeer but the technical explanation (if there really can be one) is the front wheels have less lateral grip than the rears. It can be from weight transfer, weight balance, aero balance, tire characteristics(air pressure,compound,flex), suspension (toe,camber,caster,ackerman etc.) etc. etc. on and on...but the driver can change all that in one swift jerk of the wheel or jab of the throttle.
"A more precise definition for Understeer is that the front tires are running at a greater slip angle than the rear wheels. This does not have to result in a loss of control of the vehicle. Only at the extreme edges of the vehicles performance envelope will the characteristics described above be observed.
The slip angle of a tire is defined as the difference between the direction of travel of the tire and the direction in which the tire is pointed."
http://www.madabout-kitcars.com/kitcar/kb.php?aid=59
"[BSD] There is a technical definition and the real world one. The technical definition of understeer is when the front tires have a greater slip angle than the rears. Oversteer is when the rear tires have a greater slip angle than the fronts.
In real world terms, understeer is when the car won't turn any sharper, even if you turn the steering wheel more. At some point, the front end may start to grip less even when the steering is turned sharply and the result is the car continues in more of a straight line than a sharp turn. That is understeer."
http://nsxprime.com/FAQ/Track/highperfdriving.htm
-and if you want technical, here ya go.
http://autopedia.com/stuttgart ... ysics/StuttPhysics02.html
OK maybe one of you can help me here. I've just realized that I don't even understand the simplest of all models of a car going round a corner which is the steady-state, neutral steer, two wheeled bicycle model as described in RCVD.
On p130 it is stated that if the centre or mass is exactly half way between the front and the rear contact patch and both tyres are identical then the front slip angle will be identical to the rear slip angle while the car follows a perfect, steady state circle.
Now if the car is travelling on a circle, then obviously it has a constant yaw velocity. But if the tyres and their slip angles are identical then the lateral forces they create must also be identical. Now my problem: If they are the same then where do the forces come from that make the car yaw?
EDIT: While writing the above I realized my mistake: The the car has a constant yaw velocity, not a constant yaw acceleration. This means there shouldn't be any yawing forces during steady state cornering as these would cause yaw acceleration. So I guess I answered my own question.
Yawing forces are needed to build up a yaw velocity from zero, during the transition from straight line to steady state cornering. For this torque to exist you need to have a higher force i.e. higher slip angle at the front wheel than at the rear, which is what Shotglass meant by "understeer by definition up to the apex".
On p130 it is stated that if the centre or mass is exactly half way between the front and the rear contact patch and both tyres are identical then the front slip angle will be identical to the rear slip angle while the car follows a perfect, steady state circle.
Now if the car is travelling on a circle, then obviously it has a constant yaw velocity. But if the tyres and their slip angles are identical then the lateral forces they create must also be identical. Now my problem: If they are the same then where do the forces come from that make the car yaw?
EDIT: While writing the above I realized my mistake: The the car has a constant yaw velocity, not a constant yaw acceleration. This means there shouldn't be any yawing forces during steady state cornering as these would cause yaw acceleration. So I guess I answered my own question.
Yawing forces are needed to build up a yaw velocity from zero, during the transition from straight line to steady state cornering. For this torque to exist you need to have a higher force i.e. higher slip angle at the front wheel than at the rear, which is what Shotglass meant by "understeer by definition up to the apex".
Understeer, to me means, "OMG! That wall is coming straight towards me!"
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What is understeer really?
(38 posts, started )
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