RWD rear motor , regen braking
 

Is it legal to have in the REAR ONLY REGEN BRAKING.. While in the front still disc brakes.... Since depending on the weight distribution my design would have the rear brakes might not the be biggest impact on my stopping power since the weight shifts forward.


Also could regen braking be used with the brake pedal in conjunction with the front disc brakes EITHER , slight braking use regen while harder braking uses both...

Or braking period uses both...

I don't see any legal issues with this, as long as you retain your hydraulic brakes at all four wheels and a mechanically operated emergency brake? Also, what kind of regen setup do you have, and how many g's of braking does it produce. If it's small/weak like most regen setups are, like the one in my Honda is, then your brake management system becomes simple, depress the pedal just enough to light up the brake lights and the regen kicks in at full strength which is never really too powerful... then you just press harder if you want the hydraulic brakes to kick in... Simple!

Its a future project that hasnt been started I dont know how strong it would be. But would it be road legal to have only 2 wheel hydraulic brakes those being in the front and the only way of braking in the rear be regen braking.

But its nice to see that it would work that way , whether or not I could only use 2wheel hydraulics or not. If I had to I would just have to deal with 4 wheel.

Irregardless of legality, it would be a bad idea to totally depend on a regen braking system as you've described without having the hydraulics there in case something goes wrong.

As mentioned above, you can set it up by making it kick in when the brake lights go on very easily, and I'd think it possible with the right gearing to make a good strong traction braking system to charge an onboard battery and reduce your dependance on the friction brakes. I've thought about doing something like this on my minvan (lots of space underneath and a dead axle anyway) but I would consider losing my brakes a bad idea.

FWIW locomotives have used this system for years for going down long gradients, but they don't use it as the sole means of stopping.

In general, you get ~70% of the braking power from the front, and only ~30% from the rear. So braking distance would suffer badly with rear braking only.

Its a little bit more rear sides than 70-30 being a rear engine vehicle but true. I guess I can do with all wheel disc brakes , just doing best to minimize weight on design.

I would consider your idea a good one, just keep the OEM brakes as is and add on the regen braking system to help out. And if you have ABS you can make the regen brake more aggressive than otherwise.