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Discussion Starter · #1 ·
So im driving home from work today and its a little bit rainy and a double hitch semi truck tries to make a turn across my lane to get to the opposite side of the road while im coming at him so i have to slam on my brakes (the brakes and roaters are about 4 months old) so i down shift and hit my brakes and i feel grinding or crunching on my brake pedal, my drivers side wheel locks up and my back end slides right i release my brake and straiten back out and everything is fine... but what was the grinding or crunching vibrations in the pedal what should i look into besides another brake inspection?

If it helps my brakes are also already squealing.
 

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I dont mean to be obvious, but are you familiar with how ABS activation feels like when engaged?
 

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that would be ur ABS trying to kick in.. ur wheel shouldnt have locked up.. none of ur wheels should have locked up.. how fast where you going? when my ABS kicks in i can feel it in the peddle.. but only when the wheels are actually starting to slip in slippery conditions like you described.. either all your wheels should have traction or all should be at full lock.. not all doing their own thing.

I dont mean to be obvious, but are you familiar with how ABS activation feels like when engaged?
+1
 

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could it have been your ABS kicking in? How fast were you going and how hard did you hit the brakes?
 

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4 months old? Wow. What brand rotors/pads do you have?
Jake new sig looks sweet :thumbup:

OP did you visually inspect the rotors for any shinny grind marks?
 

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Discussion Starter · #7 ·
Brakes/Rotors/Sensor: OEM installed by BMW
I was going about 45ish

Also sometimes when i go over a bump while turning (into a shopping center for instance) i feel the same thing on my brake pedal
 

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I've had abs kick only on ice/snow conditions and when there's sand on the road, never on dry pavement. Maybe i never brake that hard but yea. Abs feels like that almost, your brake pedal kicks back and forth...
 

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I would suggest OP go out in some snow with wide road margins or in a parking lot and push the car to its limits or envelope and skid around a bit to see what it feels like. that is, the ABS and handling in general. Believe it or not, when the roads are all snowy, I take my car into safe areas and purposely lose control of the car and recover. I do this over and over so I know what to expect when the car unexpectedly is in such conditions. Often when it rains, I drive without wipers to prepare for the unlikley day when the wipers go out duirng a torrential down pour and I have to drive. This allows me to be more in control and to anticipate how the car will handle under adverse conditions. This is something I picked up from flying. In training, you intentionally put the plane into bad situations (flying to the edge of the aerodynamic envelope) and practice recovering from it. The more you do it, the more desensitized you get and the more confident and in control you become when it happens.
 

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Discussion Starter · #10 ·
I would suggest OP go out in some snow with wide road margins or in a parking lot and push the car to its limits or envelope and skid around a bit to see what it feels like. that is, the ABS and handling in general. Believe it or not, when the roads are all snowy, I take my car into safe areas and purposely lose control of the car and recover. I do this over and over so I know what to expect when the car unexpectedly is in such conditions. Often when it rains, I drive without wipers to prepare for the unlikley day when the wipers go out duirng a torrential down pour and I have to drive. This allows me to be more in control and to anticipate how the car will handle under adverse conditions. This is something I picked up from flying. In training, you intentionally put the plane into bad situations (flying to the edge of the aerodynamic envelope) and practice recovering from it. The more you do it, the more desensitized you get and the more confident and in control you become when it happens.
I would LOVE to do that trust me... but ive only seen snow once in my life... born and raised Floridian :rofl:
 

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Discussion Starter · #11 ·
Jake new sig looks sweet :thumbup:

OP did you visually inspect the rotors for any shinny grind marks?
Yes i did i removed the rim and everything looked in order and there where no crevices
 

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Brakes/Rotors/Sensor: OEM installed by BMW
I was going about 45ish

Also sometimes when i go over a bump while turning (into a shopping center for instance) i feel the same thing on my brake pedal
Now that you say this i think i know exactly what your talking about. If i turn the wheel all the way to lock while, say pulling into a parking lot, and i brake a little hard i feel exactly what you described. But it has only happen when my wheel is fully turned in. Unfortunatley i have no answer for you, i have no idea what it is but its never cause me any problems as im never going more tha 2 mph when my wheel if fully turned.
 

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I would LOVE to do that trust me... but ive only seen snow once in my life... born and raised Floridian :rofl:


Give it a shot right as its beginning to rain. Roads are most slippery when it starts due to oil being lighter than water; it rises to the surface, creating a slippery surface.

anyhoo - if the road is wet try slaming hard on your brakes and see how it feels. ABS is a grinding virbrating feeling you get in the pedal and you almost feel like you mihgt be slidding on a locked wheel. Once you feel this, you shouldnt let go of the pedal but keep the pressure to ensure optimal braking as per ABS design functionality. I suspect what you felt as "locking up," was just the ABS working. It does feel like you might be locked up and slipping, but that is not the case. :thumbup:
 

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that sounds like your abs working.
abs and traction control and stability control and all the trickery in the world will not defy the laws of physics. You push hard enough the car will slide.
You performed a panic stop (not that you panicked) in the rain. It all sounds normal to me.
The wheel does lock up, even with abs, and abs unlocks it in rapid succession; however, in the right conditions that slight lock up combined with wet/oily roads can cause you to slide a little.
check out this clip and see that abs while prevents lock up it does not eliminate.
http://www.youtube.com/watch?v=ng3YjH8KaKY&feature=related
 

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Unfortunatley i have no answer for you, i have no idea what it is but its never cause me any problems as im never going more tha 2 mpg when my wheel if fully turned.
When your turn, weight is transferred toward the outside of the turn, the inside wheel will lock up easier since it has less weight on it.
Also when turning there is less traction available for braking, some of the available traction is being used to turn the car.

ABS doesn't function at less than 7 mph........

http://www.kinmak.com/downloads/doc/m3training/TSC1.pdf
ABS starts on page 40

System: Anti-Lock Braking System (ABS)
The ABS system can prevent wheel lock when braking by comparing the four active wheel
speed sensors to the average vehicle speed. If a wheel is locking during braking or has
dropped below a speed threshold programmed in the control unit ABS braking will begin.
ABS braking is possible when vehicle speeds are above 12 kph (7mph).
ABS regulation has three phases:
***8226; Pressure Build
***8226; Pressure Hold
***8226; Pressure Release


If anyone here is 16 - 21 years old, I highly recommend the Tire Rack Street Survival School to make you a better driver.
You will experience emergency maneuvers/situations in a safe environment !
http://www.streetsurvival.org/for-students.php
 

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When your turn, weight is transferred toward the outside of the turn, the inside wheel will lock up easier since it has less weight on it.
Also when turning there is less traction available for braking, some of the available traction is being used to turn the car.

ABS doesn't function at less than 7 mph........

http://www.kinmak.com/downloads/doc/m3training/TSC1.pdf
ABS starts on page 40

System: Anti-Lock Braking System (ABS)
The ABS system can prevent wheel lock when braking by comparing the four active wheel
speed sensors to the average vehicle speed. If a wheel is locking during braking or has
dropped below a speed threshold programmed in the control unit ABS braking will begin.
ABS braking is possible when vehicle speeds are above 12 kph (7mph).
ABS regulation has three phases:
***8226; Pressure Build
***8226; Pressure Hold
***8226; Pressure Release
Thanks for the info, it makes alot of sense. Come to think of it i was probably going around 10 mph :D
 

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It sounds like your abs kicking in.. But itsawkwardthat you experie±nce it when you turn to a shoppingcentre etc.. Maybe a malfunctioning abs?
 

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If you can't find snowy parking lots or gravel roads, try AutoX and you will definitely trigger your ABS even on dry, clean pavement if you just enter a tight turn too fast. Especially if you try to brake hard and turn hard at the same time on a slight downhill. And normally the worst that can happen is you hit some plastic cones. And nobody will look at you funny as they might if they see you testing ABS in a shopping center lot.
 
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