Clarification on engaging and disengaging B-mode

As all regenerative braking is also front wheels only, it is likely all your braking is front only. Friction braking dissipates 80% with front wheels so even in the best of times the fronts do almost all the work. No car works the back brakes very hard.

Until someone reports overheating the friction brakes, there is no safety issues with braking.

And no, you do not need to be concerned, all Prius have Electronic Brake-force Distribution to prevent any wheel slipping. (and I am not sure where you would need B near San Diego, Mt Palomar?)

 

I rarely used B mode, but when I drive to Ashville, NC I will engage it once or twice, especially driving home when I'm coming down the hills. The rules of thumb I use; I need to control my speed and my battery is fully charged. You can engage B mode any time, but I would use caution if the roads are wet or slick. You don't want to disrupt the traction you already have. It's best to anticipate when you'll need to use B mode and engage it before your speed gets away from you.

 

It is. You just shift whenever you want. The system decides how to actually control the engine. You're just telling it that you'd like to use the engine for some slowing.

What in the world did the dealer tell you?

 

You can shift between D and B all day long, any pedal input. The only thing that will wear is the shifter.

 

Your dealer wrong. B back to D is fine. You are correct, shift to B when you would shift to L, someone at Toyota was too honest to call it L when it does not use lower gears. (I walked the PCT east of San Diego, and was thinking of what was tall. We had a food drops in Julian and Mount Laguna.)

 

Just shift it.

There's no need to do anything special. Just go from one to the other, quick & direct.

 

Sounds like you have not done much driving in real mountains.......or have forgotten how hot the brakes can get when using them alone. Just because nobody has "reported" it doesn't mean that it won't happen.

And what the B does is apply engine compression braking which the electronic braking controls would have no control over......unless maybe you also had the brake pedal mashed pretty hard at the same time.

And as for the original question: Moving that lever to B really doesn't engage anything mechanically but sends a signal to the control computer(s) to apply engine braking. If the Toyota engineers did it right, the computer program will keep it from engaging in such a manner as to tear up the engine or motors or transmission.

And yes, applying it at an inopportune time can cause a loss of traction on the front wheels.

 

A lot of it depends on the condition of the road surface such as grooved concrete versus asphalt. You need to get the car up to speed and put it in "B" to see how it feels and what to expect. That should allow you to determine whether it's something you'd want to do when you encounter wet pavement.

 

Or perhaps the difference is that I shift to B at the top of the descent, not when I have already heated up the brakes.

I am not sure that qualifies as a real mountain, but it is where I play with B

This is more a real mountain,with those speeds on an Interstate, but I drove it in my previous Toyota, not my Prius.

 

Two ways to get into trouble.
1=wet or slippery
2=excessive speed.....on what you think is a road with good traction.

What gets you in trouble with the brakes is using them HARD for LONG periods so that heat builds up.
So first slow down with the brakes to a "reasonable" speed and then engage B and let off the brakes.......or engage B as you start down the hill.

As with a lot of other things, no need to have OCD about this, just use common sense.

 

Over the years Prius Chat gets so many questions and different approaches to using "B" that I really think Toyota needs to elaborate how and when to use it. Not just this thread but numerous ones, it seems like a lot of Salesmen, and Toyota dealership people don't even know how it should be used and employed.

For me personally, I just don't think of the Prius "dongle" as a shifter. I think of it more as a HSD input selector.
If you just tweak your thinking, then the idea of shifting from "D" to "B" while driving isn't as nerve racking.

Even though the visual set up is similar to a regular automatic transmission and we have long history of manual clutch, transmission "shifting"...the Prius knob isn't really a "shift" knob, it's much more an input selection knob.

I ONLY use "B" on long descents down big hills. Which is relatively rare for me. I do use it when it happens, but that's the only time I employ "B".