Explaining the behaviour of LSD in the wet...
Discussion
I cant get my head around why a LSD might make it trickier for me in the wet / easier to generate slide/drift (if u know what you're doing).
My understanding is the following:
When cornering, the outside wheel has to travel further (bigger radius), and therefore at a faster speed than the inside wheel. The differential will act to send the power to the wheel which is spinning fastest to accommodate this. When cornering at speed, the inside wheel has less grip (weight is on the outer wheel), and so the diff sends more/all the power to it. This is the opposite of what u want. With the lsd, it will do the reverse, ie send the power to the wheel with the most grip (outer wheel).
In the wet, both wheels may be losing grip when cornering, and while the regular diff will send power to both (?), the lsd may lock in order to maximise grip. IF this is the case, I cant get my head round why that would generate slide/drift. Can anyone explain it so someone as technically challenged as me please ?!
Thanks
Nick
My understanding is the following:
When cornering, the outside wheel has to travel further (bigger radius), and therefore at a faster speed than the inside wheel. The differential will act to send the power to the wheel which is spinning fastest to accommodate this. When cornering at speed, the inside wheel has less grip (weight is on the outer wheel), and so the diff sends more/all the power to it. This is the opposite of what u want. With the lsd, it will do the reverse, ie send the power to the wheel with the most grip (outer wheel).
In the wet, both wheels may be losing grip when cornering, and while the regular diff will send power to both (?), the lsd may lock in order to maximise grip. IF this is the case, I cant get my head round why that would generate slide/drift. Can anyone explain it so someone as technically challenged as me please ?!
Thanks
Nick
a diff splitts power till a wheel spins
then it goes from static friction to dynamic
this is a lower level of grip
this means all power goes to the spinning wheel and an amount equal to dynamic friction goes to the outside wheel usually
an LSd allows for the outside wheel to get more power by limiting power to a spinning wheel
this can overload the outside wheel and then they are both in the dynamic friction range and only producing force towards the front of the car
this means the back steeps out and without correction the car will spin
i am a real hit with the girls
then it goes from static friction to dynamic
this is a lower level of grip
this means all power goes to the spinning wheel and an amount equal to dynamic friction goes to the outside wheel usually
an LSd allows for the outside wheel to get more power by limiting power to a spinning wheel
this can overload the outside wheel and then they are both in the dynamic friction range and only producing force towards the front of the car
this means the back steeps out and without correction the car will spin
i am a real hit with the girls
Last weekend my car was sliding sideways on a straight road with a slight camber, I was beig really heavy footed and the lsd was causing both wheels to spin rather than an open diff allowing the excess power to be spun away on the inside wheel or on one wheel.
As both wheels were spinning there was no wheel left to hold the car in a straight line so it slid down the camber in the road.
Do it on a corner and you can see how there is no wheel giving you lateral grip so the back will slide away immediately.
As both wheels were spinning there was no wheel left to hold the car in a straight line so it slid down the camber in the road.
Do it on a corner and you can see how there is no wheel giving you lateral grip so the back will slide away immediately.
An LSD will allow you a lot more control over the peak point of traction, on a 1 wheel drive car (open diffed) its the first wheel to lose traction that is your limiting factor in forward momentun. LSD equipped your relying on two wheels so traction is more even, this gives you greater control over both forwards & sideways momentun 
Busa_Rush said:
Last weekend my car was sliding sideways on a straight road with a slight camber, I was beig really heavy footed and the lsd was causing both wheels to spin rather than an open diff allowing the excess power to be spun away on the inside wheel or on one wheel.
As both wheels were spinning there was no wheel left to hold the car in a straight line so it slid down the camber in the road.
Do it on a corner and you can see how there is no wheel giving you lateral grip so the back will slide away immediately.
this is the best explanation ive been given. It needs to be i jack and jil language for me! Now i think i;ve got it, and it's making sense. Many thanks. As both wheels were spinning there was no wheel left to hold the car in a straight line so it slid down the camber in the road.
Do it on a corner and you can see how there is no wheel giving you lateral grip so the back will slide away immediately.
found this website:
http://auto.howstuffworks.com/differential.htm
really good for a simple explanation (for those of us with single digit IQ's !).
it says an open diff always delivers the same amount of torque to each wheel, and the max amount is limited to the torque that can be applied to the ground. Therefore, at the extreme, if one wheel has no traction at all, and spins freely, the other doesnt spin at all and u dont move. If cornering hard in the wet, the outer wheel will not have much torque applied if the inner wheel has little traction. With the LSD, in the situation, torque can be applied to the outer wheel, while the other is spinning, which means if u boot it, the outer wheel will spin as well. Then u have both wheels spinning and big, sudden reduction in grip and u slide/oversteer. ...i think!
http://auto.howstuffworks.com/differential.htm
really good for a simple explanation (for those of us with single digit IQ's !).
it says an open diff always delivers the same amount of torque to each wheel, and the max amount is limited to the torque that can be applied to the ground. Therefore, at the extreme, if one wheel has no traction at all, and spins freely, the other doesnt spin at all and u dont move. If cornering hard in the wet, the outer wheel will not have much torque applied if the inner wheel has little traction. With the LSD, in the situation, torque can be applied to the outer wheel, while the other is spinning, which means if u boot it, the outer wheel will spin as well. Then u have both wheels spinning and big, sudden reduction in grip and u slide/oversteer. ...i think!
As above really, the benifits of an LSD in laymans terms:
at the limits of grip(usuallywhen cornering) an open (ie non LS dif) will allow the wheel with least weight over it/traction to spin (cue Clarkson in Knob Mode on the test track with the inside wheel 'schmokin' when cornering, the car follows the desired line quite safely but is not accelerating as the power is being spun away.
with an LS dif, in the above scenario, Clarkson will be demonstrating massive over steer (a new invention called "drifting" apparently)where the back of the car slews side ways, often with both rear wheels wreathed in smoke, this requires the corrective aplication of "opposite lock" to avoid the nearest ditch/tree/lamp post or in extremis a total spin.....see Clarkson in "total Knob Mode"
the above relates to a RWD car, in a FWD both scenarios end up with Humungous amounts of "understeer", where the car will try its best to go straight (for the nearest ditch/kerb/hedge/tree/lamppost).
4WD cars can experience a combination of the above.
for a skilled driver, the LSD will enable him/her to corner faster. for the inexperienced caught unawares this could lead to the introduction of the "off roading experience"
I discovered the joys of LSD in 2.8i Capris
, an experience that would be wasted on todays "yoof"........... 
wheres my zimmer frame? 
at the limits of grip(usuallywhen cornering) an open (ie non LS dif) will allow the wheel with least weight over it/traction to spin (cue Clarkson in Knob Mode on the test track with the inside wheel 'schmokin' when cornering, the car follows the desired line quite safely but is not accelerating as the power is being spun away.
with an LS dif, in the above scenario, Clarkson will be demonstrating massive over steer (a new invention called "drifting" apparently)where the back of the car slews side ways, often with both rear wheels wreathed in smoke, this requires the corrective aplication of "opposite lock" to avoid the nearest ditch/tree/lamp post or in extremis a total spin.....see Clarkson in "total Knob Mode"
the above relates to a RWD car, in a FWD both scenarios end up with Humungous amounts of "understeer", where the car will try its best to go straight (for the nearest ditch/kerb/hedge/tree/lamppost).
4WD cars can experience a combination of the above.
for a skilled driver, the LSD will enable him/her to corner faster. for the inexperienced caught unawares this could lead to the introduction of the "off roading experience"
I discovered the joys of LSD in 2.8i Capris
, an experience that would be wasted on todays "yoof"........... wheres my zimmer frame? 
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