Hybrid Car – More Fun with Less Gas

long downhill braking

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Posted by Dand on October 24, 2005, 8:28 pm
I'm about to order a 2006, but I have one concern: on a long (3+mi),
steep, winding grade in the B mode, will I have to ride the brakes
continuously to keep the speed under 25mph?  (Anyone recognize the Old
Priest Grade?)  Now, I descend in my WRX in 2nd gear (5spd man) with
occasional braking, but I have olfactory evidence of other people not
shifting down, but using brakes, and it smells expensive!

Posted by Michael Pardee on October 24, 2005, 10:47 pm

The regenerative braking should cover it mostly (depending on the total
drop) and B mode should help.

We take Hwy 89A from Flagstaff to Sedona when we go that way, about 2700 ft
loss of elevation, and just use brakes to keep the speed around 30-35 mph.
The battery fills and probably ends the regeneration somewhere near the end
of that drop. If you are dropping less than about 2000 ft it should rarely -
if ever - go into friction braking unless the speed drops to (IIRC) 11 mph.
BTW, our Classic Prius fuel economy for the round trip (including the climb
back out of the canyon) is about 60 mpg. The incline isn't as steep as you
describe, in fact it is pretty gentle, but it really illustrates the
potential advantage of hybrids.

Others in the Yahoo Prius group have reported making steep mountain descents
and their wheels being cool at the bottom.

Basically, don't worry about riding the brakes. It is more efficient than
downshifting and typically doesn't use the friction brakes at all. That's a
hard thing for me to remember, though.


Posted by dbs__usenet on October 25, 2005, 6:56 pm
Just put it in B and don't worry about it.  I've driven thousands of
miles through the California mountains and the B mode does a nice job
of keeping the car from accelerating.


Posted by Hachiroku on October 25, 2005, 10:07 pm
 On Tue, 25 Oct 2005 13:56:45 -0500, dbs__usenet wrote:

Yeah, um, that's what it's for!

Posted by Michael Pardee on October 25, 2005, 10:58 pm
In fact, a recent post to the Yahoo Prius group included this link to
pictures of his front brake pads at 8,000 miles and at 100, 520 miles. As
the text says, he couldn't measure any wear with a ruler.
(The page includes lots photos and takes forever to load... the brakes are
about in the middle of the long page.)

He doesn't indicate if he ever used "B" mode. We very rarely do, and after 3
years in and around our mountain home and 50K miles our brakes look new.
Your 2006 should do much better than our 2002 at saving the brakes.


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