Offset diff or unequal axles?

[7ishNZ]

I have a diff that has the pinion offset about an inch to the right. In the source car, the axles are different lengths to put the prop shaft in the middle of the car.

In the seven... do I want a central drive shaft or equal length axles?

[Ian7]

I have a diff that has the pinion offset about an inch to the right. In the source car, the axles are different lengths to put the prop shaft in the middle of the car.

In the seven... do I want a central drive shaft or equal length axles?

 

Without knowing the cost or installation trade-offs of your particular situation, from an engineering point of view, equal length axles will send equal torque to both rear wheels (equal twist under load).

[Hank]

Along the lines of what Ian7 is saying, most FWD cars have unequal length halfshafts and they cause torque steer when launched hard. Other than a hard launch you cannot tell the difference. For a street car it probably wouldn't matter. If you are building the car for racing purposes I would stick with equal length halfshafts and find a different rear diff. IMHO.

[Ian7]

adding to Hank's comment, if you look under decent FWD cars, you'll see the unequal length half-shafts are usually different diameters (both outside diameter and inside bore diameter) in an effort to try to equalize windup under torque.

 

having said that, this is a 7 site, and the term FWD should be verbotten anyway :-)

[TheDingo8MyBaby]

Explaining torque steer as an effect of unequal length drive shafts is only part of the picture. Torque steer is also present in equal length shafts. It is a result of the offset of the point in which a the car steers (determined through kingpin inclination) and the center of the contact patch of the tire. When tractive force is applied it will try to pull the contact patch forward causing the wheel to rotating about the steering axis. You can reduce this by adding more inclination to the kingpin which will decrease the offset between the center of the contact patch and the steering axis. The trade-off between this is that if you add to much inclination, it will load more force on the body causing instability.

 

A rwd car shouldn't stuffer from torque steer nearly as bad as fwd car (at least not in a straight line) because the drive wheels do not steer the car. Things start to get even more complicated when you're talking about acceleration during cornering.