Traction control disabling brakes over bumps

The poster said "There is an issue", not "There is a problem" (my emphasis). Whether this issue is a problem depends on the driver and your point of view. For example, the Porsche 911 is legendary for driving backward off of curves. This is because of its high horsepower and rear engine. Experienced Porsche drivers use this handling characteristic to their advantage, but it is a problem for inexperienced drivers who panic and lift off the gas. Front wheel drive caused many similar problems until drivers became acquainted with the special handling characteristics. Now most of us exclusively drive front wheel drive, so it's not a problem.

The Prius has a few quirks of its own. Being a new kind of car, and being optimized for low emissions and high mileage, it's not unreasonable to expect some differences in how it operates and handles. Those of us that recognize the braking issue but don't consider it a problem find that the brakes work within our expectations of normal braking. Those that say it is a problem consider the brake operation outside of acceptable normal limits and want to see a fix. We both may recognize exactly the same operation, but classify it differently: problem for one, quirk for the other.

Tom

 

My, my aren't we splitting hairs.
PROBLEM
4. A question proposed for solution; a matter stated for examination or proof; hence, a matter difficult of solution or settlement; a doubtful case; a question involving doubt.[Websters]

ISSUE
6 a : a matter that is in dispute between two or more parties

I'm sure the OP attached both meanings. This issue is certainly a problem for Toyota and many of its customers. We drove Toyotas for 42 years. The Prius was the only one whose brakes failed.

This issue is obviously in dispute between the true believers like you and those of us who have had problems-some serious with injuries involved.

 

I almost had a 'problem' related to brake dropout the other day.

The problem? I was going too fast for the road and traffic conditions. Combine that with a washboarded road (asphalt has shifted due to repeated heavy braking) and a blind light, and I ended up trimming down the margin of error to almost nothing.

There was a moment where it seemed like I'd be in their bumper, but firm application of the pedal did stop the vehicle. As should be evident from the above, I consider this 'near-miss' to be wholly my fault. I think the result would have been the same in other vehicles I have driven recently.

ETA: To clarify, the light was not really blind. I wasn't familiar with the intersection and turned right through a yellow. There's a T immediately after the right turn, and the light is synced with the yellow light that I went through. So basically I turned right (speeding up to go through the yellow), only to find a stopped car right in front of me.

 

There is no problem. Please, let the rest of us drive the best car out there and to the rest...drive something else that u perceive to be "better", "safer". It's pretty simple actually. Why people make such a huge deal out of stuff seems...ridiculous, at best. Have ANY of the posters that "seem" to have a problem driven other non-Prius cars over the same stretches of roadway where the Prius "fails". We need a comparison thread...

 

Personally I vote that Toyota issues another recall, firmware version DARWIN3.0. Flash all the ECUs so there is a large lapse in braking. Those that don't make it, shouldnt. Adapt or die.

 

I don't see this as splitting hairs, but as an attempt to explain why two very distinct camps have formed. I was trying to not put too sharp of a point on it, but that doesn't seem to be working, so here it is without restraint:

Some Prius drivers see a major safety problem with the Prius brakes. Those of us that you describe as true believers see this as an attempt to blame the car for poor driver decisions and lack of proper driving technique. That is the core issue, and the reason for the two distinct and well entrenched camps.

Tom

 

i haven't read this entire thread but am new to this board and have been having the car accelerating while going over bumps problem/issue for ages. the dealership acted like they didn't know what the heck i was talking about when i brought it up. i love my car. i truly do. but i'm really annoyed at these problems i'm having and the dealership acting like they've never heard of these problems i'm having before, when in fact i'm reading all about them on this board.

 

Don't expect too much from dealerships. We are no longer surprised by the lack of knowledge displayed by many of them.

As for accelerating over bumps, there are many threads about just that issue. Look (search) for terms such as "brake drop out". You aren't really experiencing acceleration over the bumps, but a loss of braking action. If you want to be technical, it is a change in acceleration, which engineers call "jerk". Your Prius doesn't go any faster, but it stops slowing down for an instant.

Tom

 

Again not just the Prius that does this. The FJ Cruiser also has this issue, and it doesn't have any regenerative braking. I'm suspecting the electric assist brakes - the FJ also has electric assist - and programming have to do with the issue

 

Too many of these threads to keep up with.

As stated above there are other vehicles out there that have ABS/TC issues like the GII Prius. FJ Cruisers. 2004 and earlier LR Discoveries. I know this behavior is correctable because when we moved from a 2004 Discovery to the redesigned LR3, the behavior was gone. Zippo. Done. Gone. Couldn't *force* it activate the TC like that if I wanted to, and I tried. So I say this is an "issue" with the Prius. And other vehicles.

Now, is it a "problem?" Depends on what you drove prior and/or if you've adjusted your driving style to compensate. Boils down to the Prius having an oversensitivity to activating the TC in NORMAL situations that can be dangerous for those coming from a vehicle without this behavior. There is no reason I should have to let off my brakes for a split second when coming to a slow stop if I'm going to hit some bumps just so I don't increase my stopping distance.

I'm not a tech, but I'm sure if Toyota were motivated, they could adjust the system - either in software or hardware - to be less sensitive. Probably all vehicles with this TC behavior have something in common - hardware/software/design or something else.

Prius drivers can help by keeping their tires at factory specs and not ballooning them up to get better MPGs. If you do, just be prepared to adjust your driving habits. The trouble is people come in here looking for MPG tips and they hear about increasing tire pressure, but have no idea it can make the TC issue worse. I think this forum should have a sticky post about the most common Prius mods/tricks for mileage and their possible effect on driving performance.

 

Me, too. It still does it, but it's much better.

But to be safe I still have to:

1. Avoid changing lanes over the little lane divider bumps while braking at any speed

2. When stopping I release the brake momentarily as I pass over bumps or rough road surface (like superstitiously lifting your feet up over a RR track, lol)

3. Brake sooner than in other vehicles in case I get caught unaware by the road surface

4. Keep my psi at factory specs - the extra savings in MPG is not worth my insurance deductible

What I've written above is good advice for any vehicle, but with my Prius, I feel it is required.