Brake problems????

I've experienced this before myself, though just consider this as something to expect and not follow too close or brake adequately in time. I've noticed it on my Prius yesterday and a couple of times on the TCH. When approaching a "T" intersection near my home they have rumble strips fairly close to the intersection. When applying the brakes there as I come to a stop (approx 10 mph) I did get a sensation that the car freewheeled just briefly. It is a little unnerving the first time. However I don't believe it affected my stopping distances by "feet" as some say they have experienced.

It's about the same but opposite sensation that I had in 2007 when I pulled out infront of traffic with a new hybrid car that had no engine running. People talked about the the non-responsiveness of the system scaring them but in reality the electric motor was applying the torque to get them moving while the ICE was kicking in. It felt scary but I don't believe any acceleration was delayed because of the system's funtion.

 

Haven't tried this - pumping brakes while in park - yet but I experienced OP's way too sensative braking just backing out of a slightly down hill parking space. Kind of felt (looked?) like comedy scene of brand new driver applying for first license at the department of motor vehicles..... Certainly not the results of rust/dirt, nor lack of braking in vehicle - 2300+ miles on Prius at the time.

 

I've often driven Ford Crown Vics/Marquis for work rental cars. They have a similar unnerving ABS behavior. Really badly startled me the first couple of times I hit a bump while stopping on a particular stretch of road that I would take.

As others described, it either felt like the car was accelerating or that the brakes weren't working. The effect was worse than anything I've yet experienced on my G2 Prius. I probably just haven't encountered the right set of circimstances, though.

All that being said, the G3 is a brand new model. There could be some slight differences in braking when compared to the G2s. For instance, my U.S. G2 has drum brakes in the back (which I actually prefer).

Best wishes,
Frank

 

I've noticed the same EXACT thing for me here in New York City and just sent an email to my dealer about it. Hitting potholes or bumps seems to trigger it. Have you gotten to the bottom of this yet?

 

Yes we have gotten to the bottom of this. Did you read the rest of this thread? I won't retype all the details again, but in short the Prius normally uses regenerative braking, which brakes only with the front wheels. Hitting a potholes or bumps can cause a loss of traction, which causes a fast transition to normal friction brakes. It is the loss of traction and transition to friction brakes that you feel. This is normal. In a panic stop this is not an issue, as regenerative braking is not used.

Tom

 

Most of us do not see this as a problem, nor do we find that the car is not stopping properly. The only stopping problem I've ever had with my 2006 came from the crappy OEM Goodyear Integrity tires. Perhaps yours is different than most.

Tom

 

Yet another reason to avoid the "guinea pig" status of being the first purchasers of a new model car, even though it is an evolutionary continuation of an established series. While many enjoy that status, for various reasons, there are enough detail engineering changes incorporated in any new model that any shortcomings require time and experience to identify and resolve.
It is traditional Development Engineering and improvements occur as feedback from the field come in.

 

Agreed! I was warned about buying a re-design. But I had faith that Toyota would get it right for the Prius. I suppose all re-designs go through this and I am sure this issue will be addresses in the next iteration.

 

Tom, you have a 2006 Prius, I have a 2008 model. While I agree these models have an entirely smooth braking transition between back EMF/ friction braking, it appears the GIII does not. This problem appears to be confined to the 2010 GIII, a new design in many respects, even though it is evolutionary in nature. New designs almost always have "teething" problems associated with revised features of the new design.

It seems from the volume of complaints listed, of which these threads are a sub-set, that the program algorithm governing the back EMF/regen/friction braking interface needs some revision in the new Prius GIII model.