Tesla Motors Club
Many have asked why Tesla didn't use hub motors in each wheel.
One argument against has been "unsprung weight" which can hurt handling.
Others have asked why not have dual motors to each rear wheel so you don't need a differential.
I found an interesting answer to this here:
http://www.worldchanging.com/archives/005118.html
"asked whether they thought about using in-wheel motors, since putting a small motor in every wheel instead of having one big motor with a drivetrain connecting it to the four wheels can greatly reduce mechanical complexity and weight, as well as improving reliability. (This is one thing EV's make possible which simply can't be done feasibly with combustion engines.) Interestingly, they did consider it, but JB said it would have made safety certification extremely difficult. It's perfectly safe, but the certification regulations are written assuming you have one motor and a drivetrain, so there are some certifications (such as the one for Anti-Lock Braking) you can't pass in a car with no drivetrain. These rules would need to be re-written to allow vehicles with in-wheel motors to be certified, which is obviously not going to happen without significant money and time spent lobbying--not a fight a small startup company should take on if it can avoid it."
We shall see if Zap runs into that issue with their Zap-X car...
One argument against has been "unsprung weight" which can hurt handling.
Others have asked why not have dual motors to each rear wheel so you don't need a differential.
I found an interesting answer to this here:
http://www.worldchanging.com/archives/005118.html
"asked whether they thought about using in-wheel motors, since putting a small motor in every wheel instead of having one big motor with a drivetrain connecting it to the four wheels can greatly reduce mechanical complexity and weight, as well as improving reliability. (This is one thing EV's make possible which simply can't be done feasibly with combustion engines.) Interestingly, they did consider it, but JB said it would have made safety certification extremely difficult. It's perfectly safe, but the certification regulations are written assuming you have one motor and a drivetrain, so there are some certifications (such as the one for Anti-Lock Braking) you can't pass in a car with no drivetrain. These rules would need to be re-written to allow vehicles with in-wheel motors to be certified, which is obviously not going to happen without significant money and time spent lobbying--not a fight a small startup company should take on if it can avoid it."
We shall see if Zap runs into that issue with their Zap-X car...