Tim.Wright wrote:GSpeedR wrote: For the most part, yes. Passive differentials, when in a locked state, will distribute torque based upon the torque reactions of the tires. So the causal effect is typically the specific tire conditions (affected by load transfer, track surface, grip capacity, etc) rather than the differential type. My logic is that if tire properties and conditions were completely equal then torque distribution will be equal regardless of the diff type (open, spool, LSD, etc). This obviously ignores asymmetric diffs, which add yaw moments any time they are engaged.
I have to disagree with this one.
Not sure which point you are disagreeing with. A passive differential
in a locked state equalizes wheel angular speeds, by definition. A clutch-type LSD, under steady-state with no input (engine) torque is very likely
not locked. My second comment is simply a matter of symmetry. I would most definitely consider wheel angular speed to be a tire "condition" (though I did state it explicitly). For a case of pure symmetry there is no mechanism for standard diff types to bias torque towards one tire.
Consider a clutch type LSD diff very common in racing. Here the output torque split will always have the higher torque on the slower moving wheel, and the locking torque is a function only of the preload and the input torque from the gearbox. It is nothing to do with the tyre.
This is certainly not "always" true. A clutch-type LSD will bias torque to the slower wheel
when the clutch-plates are slipping. When they are locked together (under significant input/engine torque) they will bias torque based on tire reactions and this may be towards the outside wheel. A spool diff can be thought of as a clutch-diff with infinitely high plate friction. So, you are correct that the ability of a clutch-diff to 'differentiate' is based upon input torque and the clutch friction, but the torque bias still must depend on the tires. If the reacted torque difference (of the tires) is not large enough to overcome the clutch friction torque then the LSD stays locked. The LSD will stay locked until convinced otherwise.
This means, under steady state cornering (no thrust), the inside wheel will be moving slower and therefore see more torque (creating an understeering torque). In the specific case where the inside wheels looses traction and spins, the faster wheel is now the inside and the higher torque is on the outside.
I'll agree with this, the maximum stabilizing yaw moment occurring at the limit of the clutch-plate friction. YM_max = Clutch_torque*track_width/Tire_radius.
A differential's behavior outside the steady-state realm (engine torque/engine braking) is also quite important.
