texbanc

Coming in to work this morning the guy in front of me threw out the anchor and I hah to get on the binders HARD. I was surprised that the brakes locked up for a couple of seconds. Is this normal? I thought ABS prevented that. I am driving a 09 GS 460.

Thanks

Tex

ibidu1

iTrader: (1)

Well ABS works by locking up the brakes and releasing and on and off pulsating

texbanc

I understand that part. What has me concerned is the tires sliding when the brakes lock up. I expected the brake petal to pulse,

KJSmitty

How much sliding/squealing did you get prior to full stop? Was it just some alternating chirps or full on skid to a stop?

Some tires make more noise than others thus identify the minor skidding associated with antilock braking - others don't. Also, if your tires are significantly warn you could get more skidding sensation with full on braking regardless of the antilocks etc. It basically takes a split second or so for the antilock system to determine what force or not it can apply to stop the car as quickly as possible yet not completely lock up the tires. This is a factor of weight, traction, speed etc. thus a minor bit of skidding first off can happen as well as throughout the stopping process.

But, if it seemed excessive (as most of us have experienced antilock break performance on several vehicles by now) it very well could justify a trip to your service dept.

Cheers

texbanc

The incident did not require a full stop. It was heavy traffic and I was able to get off the brakes before having to stop.

I do not remember this much tire skidding with my old car ( 01 GS 430)

No brake light indicators on the dash. It could be the tires, but I will have it checked.

Thanks

Tex

jamodeo

iTrader: (1)

You won't feel the pulsing of the ABS in the GS460 because our cars have ECB, when the ABS activates it flashes the traction control light to indicate that the ABS is activated.

-Joe

hacker_720

If all four tires locked at the same time the ABS wouldn't "know" the car is sliding. At least you have a more advance system which then realized you were sliding by some other method (yaw sensor / ride height / gps .. who knows) which would explain the delay. I locked up all four wheels on my old Acura TL and it just slid until I released the brakes.

It's probably functioning normally, especially if there are no warning lights on your dash during normal driving.

jamodeo

iTrader: (1)

He didn't feel the ABS because we don't feel the ABS in our cars...... ECB (Electronically Controlled Breaking, standard in the 450h, and 460) doesn't return the sensation of "pulsing" in the brake pedal, which is why he believes that ABS never activated, when in fact, it probably did.

-Joe

texbanc

Thanks Joe. The traction control light did go on right before I let off the brakes.

Tex

lucyq

I have a similar problem, front tires lock up in snow and I lose steering control. New Eagle GT all season with AA traction rating. Car is 2008 LS460.

Notice in the video the front anti-lock brakes first engage, and then malfunction as I skid to a stop (on a combination of snow/slush/and some patches of ice underneath in my driveway). Also notice the sound of the friction between the tires and snow, which indicates the conditions were not like braking on pure smooth ice.

If you have information about what would cause this, please share it with me.

Peter.

DaveGS4

iTrader: (2)

Peter if possible can you please upload video to YouTube or Vimeo? A little risky to link to a random zip file, thanks.

lucyq

Dave, I don't use youtube. File was downloaded by me from my wife's phone, and then I uploaded it to my website. Should be no malware issues. Peter.

[The video is now available in a different format, see my next post in this thread]

lucyq

Went to a different dealer, service consultant viewed my short video that proves the front brakes lock up in snow (http://www.petercdawson.us/files/IMG_0715.MOV), dealer replaced RF brake sensor wire, but it was the end of the snow season so I could not test the adequacy of this repair.

This winter the front anti-lock brakes appear to engage on snow, but the time between engage and disengage is too long (I recognize from reading this forum the LS460 will not exhibit a pulsating sensation THROUGH THE BRAKE PEDAL). Here is how I have described it to my dealer service manager:

"Since then, we have driven the car in snow several times, and found that the front anti-lock brakes do, in fact, now engage when braking on snow. However, two things suggest the front anti-lock brakes continue to malfunction[1]:

(a.) On snow, when braking the front anti-lock brakes engage in a slow engage-disengage (etc.) cycle, rather than pulsate on-and-off rapidly, such that the interval between brake engagement and disengagement is excessively long. During the long brake engagement portion of the anti-lock braking cycle, the front tires lock and slip, causing a loss of steering control and braking, and
(b.) Occasionally, the engage-disengage anti-lock brake cycle is mismatched or uneven (that is, while one front brake is engaged, the other front brake is disengaged (and vice versa), which leads to side-to-side movement of the front of the car during anti-lock braking), which worsens the loss of vehicle control during braking on snow.

During the snow storm on March 1, 2015, we experienced these two symptoms while driving on Connecticut highways and local roads. Most tellingly, because of the excessive length of time that the front brakes are engaged (during the engaged portion of the front anti-lock brake cycle)--and the resulting loss of steering control/sideways movement of the front end during the brake-engaged portion of the cycle--I pumped the brakes manually in an effort to improve control during braking on snow. My pumping action was faster than the car's front anti-lock braking, thereby improving my control of the car while braking on snow! This is evidence of two important facts:

(1.) Even though the front anti-lock brakes are now working, they still are malfunctioning, as evidenced by my pumping the brakes faster than the anti-lock brakes did, and
(2.) The road conditions were not, nor were our tires' condition, the cause of loss of control during braking [on snow], because my manual pumping of the brakes improved the braking performance during braking on snow (which would not have occurred on pure ice and/or with insufficient tire grip of the road [surface]).

This is a serious, continuing problem. Our safety is unduly at risk."

We have the certified platinum service agreement for 125,000 miles, and have requested diagnosis and repair under that agreement (even though the service department has not been able to replicate the issue ON A DIRT ROAD). In addition, given our regular brake service at Lexus dealers only, the history of anti-lock brake issues with our car (i.e., Lexus replaced a brake actuator previously[2], in addition to a brake sensor wire), the issue has continued for over a year now, and a reasonable consumer does/would expect no brake problems (apart from wear items) for a high-end Lexus LS460 for well more than 125K miles, we have reasonably requested an extension of our service agreement by 100K miles for the brakes only (not including, of course, maintenance parts).

Does (has) anyone have (had) a similar anti-lock brake problem, or technical knowledge that would help our dealer diagnose the cause? Thanks, Peter.

[1] I cannot tell whether the rear anti-lock brakes are functioning correctly on snow.
[2] That issue was: One of the front anti-lock brakes repeatedly engaged during normal braking.

chuckGS350

I have a similar brake lock & loss of steering for a few seconds as you described in (a) on slush.
I have 07GS350AWD.

lucyq

Chuck, I am still looking for a fix for this problem. Were you able to get one from Lexus? Peter.