How do you replicate braking issue - simply

I don't think this method is 100% reliable, I would have a difficult time not flooring the accelerator. :madgrin:

 

Gail,

CONGRATULATIONS! You're going to love the car. Welcome aboard and POST PICS of your baby!!!!

(On a side note, I HAVE had the brake loss happen to me, but only once. It's not a problem I worry much about as, having experienced it once in a situation that wasn't a hazardous or potentially dangerous driving condition, I now know what to expect should I hit that uneven pavement/pothole during a braking operation. So, don't sweat it. Just keep the matter in the back of your mind and, hopefully if it ever happens to you, you won't have that initial shock that has hit those of us who were unaware of it.)

 

Congraulations on your new car. You're going to love it.

 

I can recreate this at will:

- 30mph, slowing toward 10, as one might in preparation for a turn
- Braking in the regen region, HSI about 2/3 way into the skinny 'charging' section to the left
- Front tire passes over a drain grate, manhole cover, pothole, etc during the braking

Mine does it every time, like clockwork, under those and similar conditions.

 

I have tried and tried with my car under these exact conditions, and mine won't do it.

 

So, it seems to me that since there are a few here who can replicate it at will...and there are some here who have only experienced it on a rare occasion...and there are some here that say it doesn't happen at all, that it's a condition based on the individual car. Just as some have rattling dashboards and others do not. Some have the "loss of brake pedal pressure" effect, other cars do not.

Seems pretty obvious to me that it's a car-based event, and not typical for EVERY Prius. Or, should we begin to say that the rattles some have in their dashboards are just figments of their imaginations based on a few here who do NOT have any rattling???

 

Or perhaps a driver based event. Some people may be more sensitive to it than others, or perhaps tend to brake in a certain manner. My guess, and it's just a guess, is that it's most likely a combination of road surface and driver.

Tom

 

I see that you have 2010 Prius IV. Just wondering what tires yours come with it? What PSI are you running?

 

Has done it on both the original Avids and the current Green Diamond snows which are at 34psi. It seems more prone to repeat the behavior on the snows, so I suspect that tire slippage on the surface change is the instigator of the behavior. Although I should add that no traction control light appears on the dash during the event.

Of course, I expect to have a tire slip when I cross a metal surface under braking or acceleration - that is perfectly normal and expected. The difference with this event seems to be that braking is reduced to ALL of the tires instead of just the one that slips and the braking force does not come back to the same level even after the obstruction is cleared, unless the pedal is pushed much further down. So if you just hold your foot steady on the pedal as you pass over the low friction surface, the braking force is in fact greatly reduced and the stopping distance correspondingly increased.

 

i was going downhill with half my car on wet leaves.

it was like the energizer bunny...it kept going...and going....and going.

 

I had the same trouble with the wet leaves with my go-cart the other day. Those go cart brakes need to be recalled too.

 

Well yeah Tom, isn't that what the ABS system is designed to do. That is, taking the braking effort away from the foot of the driver, which will inevitably lead to wheel lockup and loss of control, to cyclic application of brake force to the point of incipient lockup at a very high rate .... say 50 cps.
As long as the wheel does not skid, you still have some control.

 

Your rear brakes are still working though, aren't they? If so, there's no loss of braking.

 

This sounds very familiar as you are describing much the same conditions that I experience it under.

 

Front brakes do most of the work so if you lose the front, and the rear continue to work, you definitely have lost some braking ability. Try using the emergency brake while moving in a car with a hand operated emergency brake and see just how ineffective rear only brakes really are.

 

I believe this is the case as well as far as requiring more brake pedal when braking returns. It is difficult to confirm because a) the event happens so quickly and b) when this happens I am approaching a stopped car or a turn and must press harder to create the stop/slow down I need.

I suspect that if this was recreated in a parking lot where you could maintain the same pedal pressure, stopping distance would easily and measurably be increased. HMMM, sounds like an experiment. Find a parking lot with an area where this could be recreated and measure stopping distance with and without the problem, say from 25 MPH to 0.