hey, well ive always heard people talk about their cars over or understeering, but never actually understood what this meant exactly? is understeer when you like turn the front wheels but the car keeps going straight sort of and over steer when u turn the front wheels and the back end slides out?
And ive heard people talking about sway bars effecting over/understeer.. eg putting one on the rear increases one or the other... which is which?
Cheers
-Viper
Over Steer and Understeer
Started by
_Viper_
, Mar 29 2006 10:00 PM
18 replies to this topic
#2
rodomo
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Posted 29 March 2006 - 10:36 PM
If the rear tyres approach their traction limit more rapidly than the front, then the effect is for the rear of the car to steer a wider path than the front wheels. This rotates the car more than the driver intended and, if nothing is done, leads to the car turning a smaller radius corner. When this occurs the car is said to oversteer.
If the front tyre approach the traction limit more rapidly, the effect is that the front of the car takes a wider radius curve than the driver intended. The car is said to understeer.
Copied from a web site.
RACV MAN
If the front tyre approach the traction limit more rapidly, the effect is that the front of the car takes a wider radius curve than the driver intended. The car is said to understeer.
Copied from a web site.
RACV MAN
#3
Racehatch
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Posted 29 March 2006 - 11:27 PM
Hi Viper,
Yeah thats a fair description (in simple terms) of understeer, with oversteer its just the reverse (funnily enough) the car will turn in more - with less turns of the steering wheel
There are various factors that will contribute to more or less oversteer/understeer - it is common to get more oversteer when you put a rear sway bar on....
Generally lsd(or locked) vs open wheel diff changes how the car will behave on turn in (and exit) of corners as well. There is also spring rates, shock tuning, whether you have front bar (and how thick it is)..... etc etc
Yeah thats a fair description (in simple terms) of understeer, with oversteer its just the reverse (funnily enough) the car will turn in more - with less turns of the steering wheel
There are various factors that will contribute to more or less oversteer/understeer - it is common to get more oversteer when you put a rear sway bar on....
Generally lsd(or locked) vs open wheel diff changes how the car will behave on turn in (and exit) of corners as well. There is also spring rates, shock tuning, whether you have front bar (and how thick it is)..... etc etc
#4
mrlctorana
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Posted 06 April 2006 - 08:48 PM
Hey Rob, never hear the term traction limit before just trying to think what it means and how it affects under/oversteer.....
Any Ideas,
Les
Any Ideas,
Les
#5
rodomo
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Posted 06 April 2006 - 09:16 PM
Traction limit is where the tyre no longer has grip and starts to slip.
Like "threshold braking" in that the tyre and the road are just starting to move against each other at different speeds. Follow?
The above was copied off a net site and the wording may confuse.
Like "threshold braking" in that the tyre and the road are just starting to move against each other at different speeds. Follow?
The above was copied off a net site and the wording may confuse.
Edited by rodomo, 06 April 2006 - 09:29 PM.
#6
rodomo
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Posted 06 April 2006 - 09:28 PM
Traction limit can refer to acceleration, braking, slide. E.g Wheel spin, where the wheel breaks traction with the road. Skid where the wheel is locked and the car is still moving. Slide or drift where the directional steering and/or drive line of the wheels (and usually the body of the car) is not in line with the arc of the corner.
Edited by rodomo, 06 April 2006 - 09:30 PM.
#7
mrlctorana
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Posted 07 April 2006 - 10:24 AM
OK got it, cheers, so it's when your on the limit of loosing traction for example driving too fast into a corner will cause front wheels to loose traction while turning causing understeer, Or if the rear wheels loose traction first the car will oversteer.
A car can also have understeer or oversteer with out loosing traction, steering box ratio, the suspension set-up ect.
Just an example, but I drive to work in my missus's Excel with power steering, then I jump into a toyota landcruiser also with power stereing and the steering ratio difference is huge. In the excel I turn the wheel about a 1/4 of a turn for a 90 degree corner, In the landcruiser it's nearly a full turn for a 90 corner.
So after jumping into the cruiser, you tend to understeer as you need to turn the wheel further for the same corner in the cruiser compared to the excel.
Les
A car can also have understeer or oversteer with out loosing traction, steering box ratio, the suspension set-up ect.
Just an example, but I drive to work in my missus's Excel with power steering, then I jump into a toyota landcruiser also with power stereing and the steering ratio difference is huge. In the excel I turn the wheel about a 1/4 of a turn for a 90 degree corner, In the landcruiser it's nearly a full turn for a 90 corner.
So after jumping into the cruiser, you tend to understeer as you need to turn the wheel further for the same corner in the cruiser compared to the excel.
Les
#8
_CHOPPER_
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Posted 07 April 2006 - 07:30 PM
And ive heard people talking about sway bars effecting over/understeer.. eg putting one on the rear increases one or the other... which is which?
A simple change of camber and castor angles can increase or reduce understeer or oversteer. It may not alter it to the extent you want, but it's a much cheaper option than playiong with sway bars. Good tyres helps a lot too.
#9
_brett_32i_
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Posted 09 April 2006 - 09:08 AM
les,
oversteer/understeer is related to the loss of traction at either end, not steering ratio.
oversteer/understeer is related to the loss of traction at either end, not steering ratio.
#10
_73LJWhiteSL_
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Posted 09 April 2006 - 12:06 PM
Someone told me once that Toranas can mix understeer and oversteer in the same corner. I never believed it till one day with the stockies on I turning from the middle of the highway into a sidestreet fairly quickly. I turned the wheel and nothing happened, the car understeered straight ahead, then suddenly the front wheels gripped and then the car oversteered and went sideways. 
With the Sprintmasters and some decent tyres the car tends to oversteer before it will understeer.
I am hopping to get the wheel alignment done, and get it setup so it hooks into corners a bit better. I guess more negative camber would help, but what other settings help turn in?
At the moment with regular rotation the tyres are wearing more evenly than the first set i had (wore out the outside edges of the fronts) but it could go further.
Steve
With the Sprintmasters and some decent tyres the car tends to oversteer before it will understeer.
I am hopping to get the wheel alignment done, and get it setup so it hooks into corners a bit better. I guess more negative camber would help, but what other settings help turn in?
At the moment with regular rotation the tyres are wearing more evenly than the first set i had (wore out the outside edges of the fronts) but it could go further.
Steve
Edited by 73LJWhiteSL, 09 April 2006 - 12:07 PM.
#11
_mervex_
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Posted 09 April 2006 - 05:05 PM
simply put, understeer is when the front hits the armco first, oversteer is when the backend hits the armco first!
#12
rodomo
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Posted 09 April 2006 - 05:25 PM
^ 
well put.
well put.
#13
_devilsadvocate_
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Posted 09 April 2006 - 06:02 PM
Once the front wheels are turned away from the direction of travel, slipping/sliding, has to occur between rubber and road with any tyre and vehicle, its just the amount that is of concern and whether the vehicle remains controllable. The faster you are going the more the slip. Most people realise this when they are going fast, but dont apply it to low speed work such as parking, when the affects of understeer are basically prevalent in all vehicles.
If you are really trying to get out a tight spot, inching out on full lock can make all the difference to those necessary inches, rather than even trying to get out at even a relatively low speed of 1kmh where slippage can see you still not getting out, the differences are far more dramatic on a slippery surface like grass or wet concrete.
If you are really trying to get out a tight spot, inching out on full lock can make all the difference to those necessary inches, rather than even trying to get out at even a relatively low speed of 1kmh where slippage can see you still not getting out, the differences are far more dramatic on a slippery surface like grass or wet concrete.
#14
_82911_
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Posted 09 April 2006 - 07:35 PM
More to the above..
Oversteer is when the passenger is shittin' bricks..
Understeer is when the driver is shittin' bricks...
Cheers Greg..
simply put, understeer is when the front hits the armco first, oversteer is when the backend hits the armco first!
Oversteer is when the passenger is shittin' bricks..
Understeer is when the driver is shittin' bricks...
Cheers Greg..
#15
gtrboyy
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Posted 10 April 2006 - 08:41 PM
LOL that is one way to descibe it. 
Edited by gtrboyy, 10 April 2006 - 08:42 PM.
#16
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Posted 10 April 2006 - 09:45 PM
Without seeing your car, I would suggest a MAXIMUM of -1.5 degres camber. More positive castor would help, but also makes the steering heavier. Start with +2 degrees castor and see how you go. 32 PSI in all tyres helps a bit too.I am hopping to get the wheel alignment done, and get it setup so it hooks into corners a bit better. I guess more negative camber would help, but what other settings help turn in?
#17
_73LJWhiteSL_
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Posted 10 April 2006 - 10:12 PM
Sorry chopper, your just 8 hours too late. Just got the wheel alignment done today.
When i take it back after 5,000ks we will see how its gone and if it needs more of anything.
Its a LJ running King Springs, Koni Adjustables and a whiteline swaybar.
Steve
When i take it back after 5,000ks we will see how its gone and if it needs more of anything.
Its a LJ running King Springs, Koni Adjustables and a whiteline swaybar.
Steve
#18
_CHOPPER_
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Posted 10 April 2006 - 10:28 PM
I'm not too late, you're too impatient!
#19
_revmaniac_
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Posted 03 May 2006 - 12:25 PM
unless of course you get into oversteer then jump outta the throttle and it snaps back and spits ya nose first into said armco....i definately prefer a slight tendancy for the car to oversteer as it only takes a slight lift of the throttle to continue merrily along the way..whereas understeer requires a very deft use of the brakes and steering and generally washes off soooo much more corner speed....very hard to get natural oversteer in a torana with a locked diff though.....simply put, understeer is when the front hits the armco first, oversteer is when the backend hits the armco first!
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