Front - Rear Torque Bias

Doug Johnson ur-quattro at
Wed Feb 18 13:18:14 EST 2004

Brady, et al.,

The differentials on pre-Torsen cars are "open," so there's absolutely no
control over torque transfer.  They either transmit torque, or they don't.

If one wheel has less traction than the other, no torque is applied to that
wheel.  Granted, this does "distribute" the torque, but it's not controlled,
or "distributed."  An open differential allows for differential rotational
speed of the two shafts connected to it, but speed is different that torque.

The fact that one wheel can turn at a different speed than the other one
connected to a specific open differential say nothing about how much torque
s being applied to the two wheels.

Torque is a "through" variable; e.g., you transmit torque "through" a shaft.
Speed is an "across variable, i.e., you measure speed across something, or
with respect to some reference point.

If you think of a rear-dive car with an open differential, for example, with
one tire on glare ice, and the other a high-friction pavement, the tire on
the ice will spin and the tire on the pavement will not turn.  In this
example, all of the torque is being applied to the tire on the ice surface.
If any torque were being applied to the tire on the pavement, that tire
would turn.  The open differential does not control torque, it allows
differential speed between axles.

Granted, these differentials can be limited-slip, but I don't think Audi
ever used limited-slip differentials, did they?


 ~ Doug

> -----Original Message-----
> From: quattro-bounces at
> [mailto:quattro-bounces at]On Behalf Of Brady Moffatt
> Sent: Wednesday, February 18, 2004 9:41 AM
> To: santoli9 at; Quattro List (E-mail); Quattro-Bounces (E-mail)
> Subject: RE: Front - Rear Tourque Bias
> I thought it was 50-50 on pre-Torsen urqs, 4kqs and 5kqs.
> Cheers,
> Brady
> Urq, 4kq, Z
> -----Original Message-----
> From: at
> [ at]On Behalf Of
> Stephen Santoliquido
> I recall some Audi literature from pre-Torsen (open center differential)
> days which described Audi all wheel drive as having a 60/40 rear/front
> torque bias.
> That is that normally 60% of the torque was applied to the rears, and only
> 40 % to the front. I understood this to have several advantages
> in terms of
> handling, and also reducing the likely hood of front loss of
> traction during
> turns, etc.
> Do I remember this correctly? A freind believes I have it backwards (60/40
> front/rear).
> Also, is this still true with Torsen?
> What about Haldex?
> Steve
> _______________________________________________
> quattro mailing list
> quattro at

More information about the quattro mailing list