Bought a new 2010 prius in June 2010. Have noticed a brief (1 second) period of brake failure (it feels like acceleration) when braking over a speedbump/pothole/etc. This occurs regularly and without fail, and is quite scary. Is this normal, or do I need to look into it further?
Normal. The tires are losing traction for a moment and it feels like acceleration. It isn't. Be sure to give yourself enough time and distance for braking on rough or slick surfaces.
The ABS software patch covered under the recall was incorporated into production vehicles started in January 2010, if I recall. Also, Toyota instructs that when the ABS engages (or feels like it isn't in this case), KEEP PRESSING - don't try to modulate the brake pedal. It does help; once the wheels are loaded again, braking will return to normal.
manufactured in 2/10. If this 1 second brake failure is "normal", than how long was the brake failure after hitting a bump before the recall? I can't help but feel that this "normal" pause in brake function is less than safe.
pb, there are many many threads debating this during the recall brouhaha. My take is that if you have an emergency, you brake hard and the regen cuts out in favor of friction. You do have ABS and such which can result in longer stopping distances (but more reliable). If not emergency stop, you know when it will occur, brake sooner, then let up at the bump, and it quickly becomes normal feeling. My wife had this happen and said the brakes are weird on bumps. I said don't brake on bumps. She got the hang of it and ours is fine. We will not get the recall flash, as I don't want more friction braking. The gen2 drivers found and studied this on their 04 models waaay back, and it was accepted as normal until the 2010 got caught in the recall debates.
I can't help wondering how many people who report this phenomenon have hyperinflated their tires to increase MPG. Stopping power depends on the area of the contact patch, which I assume varies inversely with tire pressure. I'm not criticizing higher than recommended tire pressures, but I am curious about its relation to these brief but startling episodes of ABS action.
Underinflated tires have a smaller contact patch as only the edges, not the center are contacting the surface. This is the cause of edge wear. The gap in the center also pools water which promotes hydroplaning. My 2006 at 45psi was less squirrelly on wet pavement when braking.
Are you saying that while braking properly you lose literally a FULL SECOND of time in which you have no braking?
it feels like 1 full second, but maybe it is half a second. I guess what I'm wondering is, is this how it is supposed to feel after the recall/patch, or is this how it felt before the recall/patch. In other words, did my car somehow get overlooked in fixing whatever the braking problem was?
It feels the same before and after the patch, only the length of the dropout is reduced. This makes a comparison very subjective, which is hard to do with typed words. It's like saying "How blue is blue to you?" Tom
Yeah, after hitting the bump, the moment he leaves the ground the brakes don't work FYI, places not to apply the brakes: 1. on a bend 2. on a rough surface 3. on a bumpy surface 3. on icy or oily surfaces If you encounter any of the above, it is advisable to brake before you get there or if it's too late then steer (smoothly/gently) only. This applies to all vehicles not just the Prius. IMO the Prius is just doing what any othe ABS equipped car does when the driver is doing what he shouldn't.
I think calling it "Brake failure" is overstatement since the brakes are working and you can still stop the car. However, if the car has the recall fix at the factory or wherever, I don't think you should be feeling the sensation like the brakes aren't working properly after a bump. That is a known problem that Toyota made a fix for. Simply take it back to the dealer and have them check it under warranty.
