Ideal toe out for drive wheels?

Just had my alignment done last week. Left toe was -0.27 meaning the front of the front wheel was pointed slightly outward. Right wheel was at .01.

It is good to have some toe out or negative toe on the drive wheels of a car. The reason is that the drive wheels pull or push the car forward resulting in a forward bias on the drive wheels where they are pulled further in front of the car when providing power than when at rest.

Ideally the toe would be set just negative enough that at whatever cruising speed the car spends most of it's time, the total toe would be 0.0 at cruise. The faster the car is likely to be traveling, the more negative toe at rest is needed.

Does anyone have any knowledge or evidence of what the best total toe out or total negative toe should be?

Obviously the only way to know for certain would be to measure toe while driving, but we can't do that. The next best thing would be to measure the amount of toe change when x amount of force is applied to the front wheels from behind while on the alignment rack equal to the amount of force needed to keep the car moving at y number of miles.

Clearly I'm not going to be able to get an alignment shop to do that either.


Perhaps Toyota has already figured this out and someone on this forum will know. Or perhaps there's a generally good known answer for front wheel drive cars with suspension geometry similar to a Prius?

 

Stability when braking is certainly a good factor to consider when balancing best possible MPG with safety.

I shimmed my rear wheels this weekend and will take it back to Firestone to have my alignment rechecked with liftetime alignment there.

The shims were very straight forward to put on. It really only takes about 30 minutes per side. I could see an expert who does it a lot doing it in 15 minutes per side.

My rear total toe in was 0.6 degrees. With the shims, it should be about 0.16 degrees now.

Noticed no difference in handling before and after.