Bench build AWD Mini

Robbie said:

In reply to Ransom :

I think torque steer being caused by unequal length axles is 99% myth. Their diameters are small so the rotating effect is similarly small.

I don't think it's rotating mass that's the issue.  I think it's unequal torsion in the unequal-length halfshafts, that then gets compounded by bushing compliance.

Duke said:

Robbie said:

In reply to Ransom :

I think torque steer being caused by unequal length axles is 99% myth. Their diameters are small so the rotating effect is similarly small.

I don't think it's rotating mass that's the issue.  I think it's unequal torsion in the unequal-length halfshafts, that then gets compounded by bushing compliance.

Torque steer is caused by the unequal length axles acting like torsion springs. Two shafts of equal diameter, equal length would be equal springs and would flex equally. When one is longer it has an effective lower spring rate meaning it will twist more essentially sending more direct power to one side. I also imagine that then the suspension reacts differently which could also compound the issue.

while this stuff about a longer axles being a different torsional spring sounds true, I have a hard time believing it has a larger impact than the steering input initiated by losing traction in one wheel.

A tire going from static friction to dynamic friction could cause a traction loss of 20% or more. Is the difference between 2 axles going to approach even 1 or 2%?

Do you notice that torque steer only ever pushes you one way? or does it push you both ways sort of randomly? One axle is always longer than the other on a given car.

In reply to D2W :

Interesting. I always assumed torque-steer was caused by one tire getting power and trying to pull ahead of its partner (because it’s partner is just going along for the ride).

I can’t fathom an axle acting like a torsion bean to the extent that it causes torque-steer. That seems like way too much twist for an axle to handle without snapping.

An extreme example being how a tracked vehicle steers.

use a jag or BMW differential as the transfer case? This could put the engine more "inline" with the centre of the car as you could mount it 90 degrees off of where you have it now. Being in the middle of the car, you just run half shafts fore and aft to the axle diffs

Motorcycle engines make poor car engines. Why not just copy Project Binky ?

In reply to loosecannon :

Because you'd end up working on it for years and only have half a car. 

Going off the reservation here but to address the original concerns of the OP how about a rear/mid engine front drive set up. 

Robbie said:

while this stuff about a longer axles being a different torsional spring sounds true, I have a hard time believing it has a larger impact than the steering input initiated by losing traction in one wheel.

A tire going from static friction to dynamic friction could cause a traction loss of 20% or more. Is the difference between 2 axles going to approach even 1 or 2%?

Do you notice that torque steer only ever pushes you one way? or does it push you both ways sort of randomly? One axle is always longer than the other on a given car.

My son has an SRT4. They are notorious for torque steer. It also has a limited slip that is tight enough to do lay down two black lines. It definately pulls more to the left. While I'm sure that an open dif could also contribute to the problem you can get torque steer without ever spinning a tire.

In reply to dean1484 :

Probably a big stretch, but I imagine such a setup having the worst of both worlds. Weight transfer on hard acceleration encouraging wheelspin and/or understeer, and rear weight bias encouraging oversteer during trail braking.