kick out

[mrjones]

Hello All
With a rear wheel drive, open diff. Why would the back end kick out to the right when accellerating too hard, and not just spin the one traction less wheel?
Ian

[reggie82]

Because you are using grip from both the rear tyres to stop the back of the car sliding out. So when you break traction on one tyre, the other tyre doesn't have enough grip to hold it on it's own.

[mrjones]

that makes sense. but why does it allways kick to the right.

[Major Fallout]

Suspension geometry, one wheel with less grip or more toque will always be the first to spin.

[xRIEx]

mrjones said:

that makes sense. but why does it allways kick to the right.

Because of the right hand grip rule?

[crosseyedlion]

My open diff e36 328 sport (with decent, wide tyres) has been known to kick out either way on occasion, although most of the slideyness from this car comes from weight transfer. You might have traction control that brakes the spinning wheel (mine does) which can sometimes cause it to kick out a little when it would otherwise spin up a wheel.

Even without an lsd, you cant fight physics. Its the same as why in a FWD from low speeds car you (often) cant bury the throttle, apply full lock and expect it to turn with a wheel spinning. Instead its a horrible smokey understeery mess.

[JAHetfield]

Man up, split the diff and weld it up.

[NHK244V]

mrjones said:

Hello All
With a rear wheel drive, open diff. Why would the back end kick out to the right when accellerating too hard, and not just spin the one traction less wheel?
Ian

Cos of the rotation on the prop forces one side of the axle down and one side up giving less grip on the upside and more on the downside ?

[McSam]

reggie82 said:

Because you are using grip from both the rear tyres to stop the back of the car sliding out. So when you break traction on one tyre, the other tyre doesn't have enough grip to hold it on it's own.

Yep - if the inside tyre starts to spin up and loses its ability to support the lateral cornering load properly, then all that lateral load goes to the outside tyre, which is also trying to accelerate the car, and is overloaded. It will start to slide sideways under the load, and as this breaks its grip and so lowers its abilities further, it'll spin up a bit too.

Just as in a FWD open diff car, if you floor it while attempting to turn you'll run wide because the inside wheel spins, leaving the outside wheel to deal with all the lateral loads, which it can't do.

[crosseyedlion]

I think most would agree its a good thing, embrace it

[PHmember]

xRIEx said:

mrjones said:

that makes sense. but why does it allways kick to the right.

Because of the right hand grip rule?

^^This^^

On the continent it always goes to the left - or is that south of the equator? One of 'em anyhow....

[NHK244V]

McSam said:

Yep - if the inside tyre starts to spin up and loses its ability to support the lateral cornering load properly, then all that lateral load goes to the outside tyre, which is also trying to accelerate the car, and is overloaded. It will start to slide sideways under the load, and as this breaks its grip and so lowers its abilities further, it'll spin up a bit too.

Just as in a FWD open diff car, if you floor it while attempting to turn you'll run wide because the inside wheel spins, leaving the outside wheel to deal with all the lateral loads, which it can't do.

Except he not on about cornering but from a standing start ? i assume as he uses the term "kickout" rather than oversteer.
on a FWD thats torque steer, mainly caused by unequal length drive shafts.

[davepoth]

NHK244V said:

Cos of the rotation on the prop forces one side of the axle down and one side up giving less grip on the upside and more on the downside ?

Probably this. Here's some science on the matter.

http://www.hotrod.com/techarticles/chassis/chassis...