2010 brake system

Discussion in 'Gen 3 Prius Technical Discussion' started by bwilson4web, Jan 30, 2010.

?

Details on braking anomoly

Poll closed Feb 13, 2010.
  1. Happens in the beginning of braking

    19.4%
  2. Happens after braking for a bit

    79.1%
  3. Had a load in back of Prius

    1.5%
  4. No significant load in Prius

    70.1%
Multiple votes are allowed.
  1. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Hi folks,

    In light of the announced, upcoming 2010 fix, I'd like to first:
    Thank YOU!
    for everyone who contributed:

    1. Addresses and locations of the problem places
    2. Accurate descriptions of what happened
    3. Patient with my plodding pestering about more details
    Of course on this great day, I finally got the accelerometers I'd ordered to debug the problem. But that is OK, I have another use for them ...

    CLEAN UP


    My plan is to:

    1. Collect the last of the brake problem location photos and images.
    2. Ask folks who contributed to report "before" and "after" impressions. In engineering we call this 'regression testing.'
    3. Low-keyed collaboration on understanding more engineering data - I have these accelerometers and a couple of months before . . .
    So this is a happy day, a fix is coming, and I couldn't be happier. Hummm, guess I should clean out my "Ignore list" of the folks who only added noise, no facts and data, . . . or maybe not.

    Thanks again,
    Bob Wilson
     
    1 person likes this.
  2. Earman

    Earman CDN Prius III Technology Blue

    Joined:
    Jun 22, 2009
    78
    11
    0
    Location:
    Vancouver, BC, Canada
    Vehicle:
    2010 Prius
    Model:
    N/A
    Thanks for the great work Bob and for making this problem more understandable to the lay person like me!

    I hope the fix will be available in Canada as well, the news speaks about Japan and the US but not about Canada... They say there has been only one official complaint in Canada!
     
  3. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Well my Gulf Coast Data Concepts, X6-2, arrived today ... just in time to get detailed data about what happens when a ZVW30 Prius drives over a speed bump at ~30-20 mph while the brakes are lightly applied:
    [​IMG]
    This is the first set of data also used to understand the device, calibration and orientation. The Az is gravity and as the car hits the speed bump, there is an initial acceleration up. Once the car is headed up, it returns at a partial G until it impacts the pavement again. There may be a dampened shock absorber cycle or possibly some part of the rear wheels impacting the speed bump.

    During these G variations, the stopping force varies but only up and down from zero to the approximate braking force. Then as the car suspension begins to recover, the braking force evens out. There is no evidence in this test of any reduced braking effect beyond the actual bump. But this is not definitive but just a single observation.

    I'm not ready to loan these recording accelerators until I have some software to reduce the data, handle calibration, and minimize noise. Also, a secure mount is needed and clear instructions. I also need to study our ZVW30's data to see if there may be some testing profiles that may replicate the reports of others. Although Toyota plans to release a fix, it is always nice to have a baseline to compare before and after data.

    Obviously, I have too many fun toys for boys.

    Bob Wilson
     
    4 people like this.
  4. librapoppy

    librapoppy New Member

    Joined:
    Jan 17, 2010
    2
    0
    0
    Location:
    Chicago
    Vehicle:
    2010 Prius
    Model:
    IV
    Here are the coordinates from google maps. I was driving a week ago going east on grand avenue around this intersection, when I lost control momentarily on my 2010 Prius IV.

    41.924503,-87.810038
     
  5. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Thanks!

    Like this, looking NorthWest:
    41.924503,-87.810038 - Google Maps

    Or this, looking SouthEast:
    41.924503,-87.810038 - Google Maps

    BTW, I am not going to comment on the quality of those streets since no doubt those who travel them already have ... strong opinions.

    Bob Wilson
     
  6. hill

    hill High Fiber Member

    Joined:
    Jun 23, 2005
    16,153
    5,992
    54
    Location:
    South OC So Cal & Nashville, TN
    Vehicle:
    2004 Prius
    Model:
    IV
    Maybe the poll should include a couple more answers:

    "It never happens, but I'm a very very cautious conservative driver"
    "it never happens no matter how hard I try to force it to happen"


    .
     
  7. sliminbay

    sliminbay New Member

    Joined:
    May 27, 2009
    1
    0
    0
    Location:
    SF
    Vehicle:
    2004 Prius
    Model:
    IV
    Has anyone experienced brake surging in the morning just before the motor kicks on? Once in a while, my 2010 prius bucks like a bronco pulling out of garage in reverse.
     
  8. Analogkid1958

    Analogkid1958 Member

    Joined:
    Jul 30, 2009
    118
    61
    0
    Location:
    Yorktown, IN
    Vehicle:
    2017 Prius
    Model:
    III

    Thanks! I've experienced this "weak" ABS, too. Completely unlike my Dodge Caravan and Honda Civic, with their typical very fast pulse. Dealer checked and reported it was within spec, so I took it to an icy parking lot and figured out what it feels like. I've adapted, but am not completely convinced it's what it should be.

    I have also experienced the long time it takes to come out of cruise control - it really feels like the car is accelerating though I know it's not.

    Similarly the transition delay. Really disconcerting. Thankfully it's only happened a couple times.

    I'm looking forward to the day when we can plug a USB cable into the dashboard, to our computer, and get software updates on the web! Until then, I'll wait for the recall email / letter.
     
  9. Analogkid1958

    Analogkid1958 Member

    Joined:
    Jul 30, 2009
    118
    61
    0
    Location:
    Yorktown, IN
    Vehicle:
    2017 Prius
    Model:
    III
    WOW! Thank you, Bob! I think Mythbusters might be hiring!
     
  10. Analogkid1958

    Analogkid1958 Member

    Joined:
    Jul 30, 2009
    118
    61
    0
    Location:
    Yorktown, IN
    Vehicle:
    2017 Prius
    Model:
    III
    Bob,

    I understand you'd need many runs on this to get a decent sample, but if you took a "best fit" curve through the spiky parts of Ax, wouldn't you see a dip (increased acceleration) about the same time the car is on its way back down (rebounding)?

    Is this enough to be what we might be feeling?

    Help talk us data-newbies through this, please. Thank you again!
     
  11. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    The posted graph is normal braking going over a speed bump. The blue line is braking acceleration, actually deceleration of the car. There is no evidence of a delay in braking force after having passed over the speed bump. During the bump there are some changes but they have more to do with loss of traction than anything else.

    This first graph is just to get the data and get a feel for how the instrument works. More will be coming but I have to hack a Perl program to reduce the data.

    I have a volunteer who can replicate the anomaly. His data should show the problem. But first I have to 'master the tool.'

    Bob Wilson
     
  12. Lewie

    Lewie Junior Member

    Joined:
    Nov 22, 2009
    89
    18
    0
    Location:
    San Diego CA
    Vehicle:
    2010 Prius
    Model:
    V
    I think you might be able to collect better data by going over a different kind of bump than a "sleeping policeman". I've had good success going over a disjointed cement patch, where the cement forms an ascending ramp followed by a sharp drop-off of an inch or so. I also experienced the float where a bridge deck was a bit higher than the approach pavement. Once again, it's a sharp drop of an inch or so. The advantage of measuring acceleration in the bridge case is there won't be any vertical signal until you drop off the edge, then the signal should be cleaner with less bouncing. I've also found that I can't recreate the float over regular rough-road bumps at low speed since the wheels don't loose contact with the road. But the edge-drop bump guarantees a regen dropout right down to the normal dropout (7-mph?) speed.
     
  13. ronhowell

    ronhowell Active Member

    Joined:
    Oct 4, 2007
    681
    32
    0
    Location:
    Cypress, CA.
    Vehicle:
    2008 Prius
    I'm not! Individual freedom to do this kind of thing in a computer is one thing, but in a 3000 lb vehicle it scares the heck out of me. Besides, I am sure such behaviour would immediately invalidate your warranty.
     
  14. LINKSTER

    LINKSTER LINKSTER

    Joined:
    Jul 5, 2009
    20
    0
    0
    Location:
    los Angeles
    Vehicle:
    2010 Prius
    Model:
    IV
    I have been writing about "grabbing brakes" since July. I have a 2010 class four. At least three to four times a week, when I go into reverse and the car starts back and I gently apply the brakes to slow the car the brakes "seize" not grab. They bring the car to an abrupt halt. So I release the brake and try again with the same result. I found out later that when this happens, if I drive as little as 12 inches forward something releases and the car backs up perfectly normally. I know that in reverse the brakes are controlled electrically.

    After numerous complaints, Toyota came out to my dealership in Santa Monica, CA and drove my car for two hours. I told them in an advanced letter that I can not make it happen and that it's random and unpredictable. They said they could not duplicate the problem- "a standard military maintenance answer".

    I am a retired Air Force and airline pilot (747's, DC-10's, C-130's etc). I surely understand how to brake a 700,000 lb aircraft and I know a braking problem when I experience it and this car has one, even though I can't make it happen. Trying to live around a malfunction is not an answer.

    Linkster
     
  15. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Are you willing to spend $90 on an accelerometer and a couple of hours to document it?

    If so, contact Gulf Coast Concepts and order their cheap accelerometer. I'll be happy to share "lessons learned'.

    Bob Wilson
     
  16. LINKSTER

    LINKSTER LINKSTER

    Joined:
    Jul 5, 2009
    20
    0
    0
    Location:
    los Angeles
    Vehicle:
    2010 Prius
    Model:
    IV
    I would be happy to, but what is it I would learn from it?

    Linkster
     
  17. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    It is the difference between flying by seat of the pants and using instruments ... say airspeed indicator. Let me give an example with one of my first measured speed bumps recorded by the accelerometer. :
    [​IMG]
    The red line is vertical acceleration and the force of gravity. The blue line is acceleration along the axis of the car. Due to the orientation, a positive value is application of the brake. So the bump is the variation in vertical acceleration but other than temporary, momentary brake force changes, after the bump, the car continued to decelerate. We have engineering units that can be used to quantify exactly what is going on. A "siezed" brake would show a very sharp, deceleration.

    Now you may remember from physics that:

    • integrating acceleration -> velocity + constant
    • integrating velocity -> distance + constant
    So using the same data, I was able to generate this chart:
    [​IMG]
    The "blue line" is the double integration of the acceleration and shows when the front tires hit the speed bump, the struts compress and the cabin rises ~2.5 cm. Then the rear wheels hit and suddenly the cabin is 5 cm. higher ... the height of the speed bump.

    Now the reason I bring this up is an accelerometer converts imprecise words into numbers, engineering units. You no longer have to say "seize" but instead:

    • normal reverse braking is "n meters/second**2"
    • abnormal reverse braking is "m meters/second**2"
    One thing I didn't ask, have you gotten the maintenance manual that covers the brakes? In particular, the parking brake adjustment mechanism? Parking brakes are typically self-adjusted by braking while in reverse.

    If you can get the maintenance manual, you might be able to figure out what is going on. Perhaps even jack up the rear, take the tires off and inspect the parking brake adjustment mechanism. But none of this has anything to do with the "brakes going away after light braking over some road surfaces."

    This is the "Prius Technical Forum," which typically means not just reporting a problem but doing something about ... mastering the technology. So you have options.

    Bob Wilson
     
  18. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Well finally it happened to me so I voted. This after 8,500 miles and spending the last six weeks trying to replicate the problem. Fortunately, I had the accelerometer running and captured the event.

    CONDITIONS

    Friday morning, ~8:30 AM, light drizzle, approaching the Martin Road entrance to Redstone Arsenal. There are two speed bumps and the first one exhibited the braking anomaly:
    [​IMG]
    The "red" markers are gravity and the speed bumps. The "blue" line is negative for braking and positive for acceleration. It includes coming to a complete stop for the badge check. BTW, I've been over that speed bump many times without a problem.

    Expanding the scale a little better:
    [​IMG]
    This clearly shows braking ceased and then came back. I had a sliding sensation that is common on rain slick, Huntsville streets. Even now, I don't know if the braking system stopped or the tires just slid until they regained traction. Regardless of the specific mechanics, there was a definite pause. But some of the linear data points suggest brief acceleration.

    I expanded the scale again and ran trendlines that averaged 16 points together:
    [​IMG]
    The trend line shows no evidence of 'acceleration' but it is clear braking forces ceased for about 800 milliseconds.

    I'm uploading the spreadsheet with the data. Feel free to join in data analysis.

    Bob Wilson
     

    Attached Files:

    telmo744, PrBuddy, joewein and 2 others like this.
  19. adrianblack

    adrianblack Member

    Joined:
    Sep 26, 2009
    447
    187
    0
    Location:
    Los Angeles
    Vehicle:
    2010 Prius
    Model:
    III
    Bob, would you say you kept pressure on the brake pedal relatively constant during the event? And did you hear any evidence of ABS solenoid activation?
     
  20. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    23,277
    13,108
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    I believe the brake pressure was constant. I was approaching the gate and needed to reduce my speed. So I was braking before hitting the speed bump and it is not my practice to try and modulate the brakes when going over a speed bump. You'll notice that when braking force returned it was similar to the pre-bump level.

    I remember no evidence of ABS activation but within the interval of transiting the speed bump, I personally couldn't tell. That is one reason for using the accelerometer. Once the speed bump is past, I felt a slipping motion (aka., slip and slide.)

    Bob Wilson
     
Loading...