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Violent shudder when braking after hitting bumps

116K views 417 replies 124 participants last post by  bobdmac 
#1 ·
I've noticed that my car shudders badly when braking while passing over larger road imperfections (expansion joints, potholes). My Integra is fine when I go over the same. Is there something wrong with my 525iT or is this just normal for the car?
 
#2 ·
LA525iT said:
I've noticed that my car shudders badly when braking while passing over larger road imperfections (expansion joints, potholes). My Integra is fine when I go over the same. Is there something wrong with my 525iT or is this just normal for the car?
Is it only after hitting bumps, or does it do it all the time while braking? Shuttering under braking tends to be warped rotors. How many miles on the car/brakes?
 
#3 ·
hmmmm........that happened to me last week. I did a hard brake after I went over a small ditch and all of a sudden, the car started to have a seizure or something. But it was just that one time. My car has over 98,500 miles. I've been more cautious whenever I brake now. I'll keep tabs on that to see what gives........
 
#5 ·
Plaz said:
You sure it's not just the ABS activating?
you could be correct
 
#299 ·
That's my bet as well.
 
#6 ·
Plaz said:
You sure it's not just the ABS activating?
I'm not braking hard, usually just downshifting and gently braking to a stop (I'm talking about an expansion joint on the Main Street bridge over the 10 freeway in Santa Monica).

Could be the ABS triggered, but seems like a much more pronounced shudder through the pedals.

Car has 18,000 miles on it, 1.5 years old and I'm the original owner.
 
#7 ·
LA525iT said:
I'm not braking hard, usually just downshifting and gently braking to a stop (I'm talking about an expansion joint on the Main Street bridge over the 10 freeway in Santa Monica).

Could be the ABS triggered, but seems like a much more pronounced shudder through the pedals.

Car has 18,000 miles on it, 1.5 years old and I'm the original owner.
If you applying any brakes and go over a bump that's the ABS kicking in and you would only feel it throguh the pedal. It feels like the pedal is pushing back against you because it actually is. The brakes are pulsating so that they do not lock up on you. This is normal for every car with ABS, I would imagine that your integra is not equipped with ABS. If you feel a vibration under normal braking conditions at highway speeds that is most likely due to warped rotors as previous poster stated. You have driven more than enough miles to have warped your rotors.
 
#9 ·
LA525iT said:
I'm not braking hard, usually just downshifting and gently braking to a stop (I'm talking about an expansion joint on the Main Street bridge over the 10 freeway in Santa Monica).

Could be the ABS triggered, but seems like a much more pronounced shudder through the pedals.

Car has 18,000 miles on it, 1.5 years old and I'm the original owner.
LA I know exactly what you are talking about, it is the ABS activation but very odd in deed, not the normal ABS activation, but a whole front end shuttering, and does not stop after you go over the bump, until you release the brakes.

It almost feels like the whole front end is going to shake apart.

It has happened to me 3 or 4 times in my 2001 530i and 2 or 3 times to me in my wife's 2000 740i, so I have never brought them in on this. Funny, they replaced the ABS/DSC computer in the 740 not to long ago, and it still happened. I have never asked about it but will next time.

But you are right, it is unlike any other car I have ever owned with ABS (I have had 4 others), it is not just a pulsating feeling through the pedal or a pump sound, or clicking sound, the whole front end shutters and bucks back and forth.

The 7er has less than 40k miles and my 5er has over 50k miles, I just thought it was normal, but alarming, under certain conditions (and not braking hard either). Maybe a software glitch.
 
#130 ·
Had the same exact issue once. Mine at low speed (about 35MPH) I was braking, hit very rough road, steering shuddered like mad, off brakes, on brakes now OK. It was NOT ABS kicking in. It is the infamous BMW suspension that is overly sensitive. All you have to do is read the ba'zillion posts on steering wheel shake to realize that this is the price you pay for superb handling on the E39 series.
 
#10 ·
How can you expect every car to have the same exact ABS feel? That's like expecting every car to have the same steering feel. The know what ABS feels like when it kicks in on a car. I can't say that I can recognize the severity between this car and my previous cat but you should know what the ABS feels like and its as simple as that. Maybe there is a combination of the ABS and your rotors being warped.

When was the last time you guys changed your rotors? People you have bad braking habits (people who over brake or apply brakes by holding the brake down until they are at the speed they wish rather than applying brakes and releasing them allowing inertia to do its work) go through brakes and rotors quicker and tend to warp their rotors because they are always hot.
 
#11 ·
dagoo98 said:
How can you expect every car to have the same exact ABS feel? That's like expecting every car to have the same steering feel. The know what ABS feels like when it kicks in on a car. I can't say that I can recognize the severity between this car and my previous cat but you should know what the ABS feels like and its as simple as that. Maybe there is a combination of the ABS and your rotors being warped.

When was the last time you guys changed your rotors? People you have bad braking habits (people who over brake or apply brakes by holding the brake down until they are at the speed they wish rather than applying brakes and releasing them allowing inertia to do its work) go through brakes and rotors quicker and tend to warp their rotors because they are always hot.
Dagoo

Sorry, my rotors are not warped. When the steering wheel pulls left and right repeatedly until the brakes are released (even after the bump has long passed) and the whole car shutters badly at that same time, I know that it is not normal, have I complained, no, does it happen every time, no, but it does happen sometimes when I brake and go over a bump, and not heavy braking, not limit braking, but well modulated braking.

Rotors were replaced (full brake replacement) only 3k miles ago on my car and 10k miles on the 7.

Relax on criticizing others, we know what we are talking about.

Yes, not every car has the same abs feel, but whole car should not shudder, vibrate, or pull when abs kicks in (plus I have felt normal abs kick in on the car, so I know it is not the normal application).

If even you were driving my car when it happened, you would be quite alarmed the first time!

Be constructive, not destructive - Thanks
 
#12 ·
I have let two people other than my wife drive the 5er. The first and only time my buddy drove it he entered a liquor store drive way (small bump) while putting on the brakes and the front-end-about-to-come-apart ABS activated. He looked at me like he just wrecked my car.

I am sure dagoo didn't mean his post the way it sounded, but if I am coming to a stop and there is a pot hole that I know might cause this phenomenon, I guess I should just disengage the brakes and coast into the back end of the guy in front of me. I am just glad that other people find the ABS in these cars a bit eccentric.
 
#13 · (Edited)
Yeah must be the ABS I guess. My Integra has ABS (and a firmer suspension and shorter wheelbase to boot) and does not react at all over the exact same road imperfections.

BTW, rotors are not worn nor warped. My car only has 18k on it and I slow down with a combination of downshifting and gentle braking, so I'd bet my brakes are much less worn than a car with similar mileage and an automatic tranny.
 
#14 ·
I have experienced this very problem in my '02 525i. Usually at low speed going over a railroad crossing or the like. I think its just ABS kicking in. I usually let off and reapply, and no problem.
 
#179 ·
Ditto...on my 2002 530i. I thought the front left wheel was going to fly off! Seems to only happen at low speed breaking and hitting a small road bump. I have had the suspension checked with no problems found. Let off brakes and stops immediately. Glad to know that its not just me.
 
#16 ·
I've experienced this in my car several times as well. It's as if the ABS doesn't *let go*. Usually it's an expansion joint or a mild pothole and usually I'm driving no more than 5 miles per hour or so. The ABS kicks in and will not *let go* until either the car is fully stopped or the mechanism is "reset" by taking my foot off the brake pedal.
 
#17 ·
shabbaman said:
I've experienced this in my car several times as well. It's as if the ABS doesn't *let go*. Usually it's an expansion joint or a mild pothole and usually I'm driving no more than 5 miles per hour or so. The ABS kicks in and will not *let go* until either the car is fully stopped or the mechanism is "reset" by taking my foot off the brake pedal.
Exactly, thanks to you and the others for your replies, at least I know it is not just my car :thumbup:
 
#19 ·
E39spd said:
Dagoo

Sorry, my rotors are not warped. When the steering wheel pulls left and right repeatedly until the brakes are released (even after the bump has long passed) and the whole car shutters badly at that same time, I know that it is not normal, have I complained, no, does it happen every time, no, but it does happen sometimes when I brake and go over a bump, and not heavy braking, not limit braking, but well modulated braking.

Rotors were replaced (full brake replacement) only 3k miles ago on my car and 10k miles on the 7.

Relax on criticizing others, we know what we are talking about.

Yes, not every car has the same abs feel, but whole car should not shudder, vibrate, or pull when abs kicks in (plus I have felt normal abs kick in on the car, so I know it is not the normal application).

If even you were driving my car when it happened, you would be quite alarmed the first time!

Be constructive, not destructive - Thanks
My reply was constructive, the scenario you described are exact symptoms of warped rotors. Remember that the people on this forum cannot drive the car to tell themselves so they go by your descriptions. When a car has warped rotors, when you apply brakes at highway speed, 50mph and above, the steering wheel shakes from left to right and you feel the vibration in the front of your car until you let go of the brakes.

The fact that you brake and go over a bump should first clue you in on the fact that it most likely is your ABS kicking in. It also will not stop until you release the brake because that is what is designed to do, the whole purpose is to prevent the brakes from locking up and causing an unsafe condition. It forces the driver to release the brake and re-engage the brakes which ensures that the brakes will not lock up because of the bumps in the road. I simply was trying to explain that it was either your rotors being warped or your ABS kicking in, not quite sure how that's destructive.

I don't understand when people post here looking for answers and then get offended when others offer answers. :confused:

Thank you norcal 528i for understanding the intentions of my reply. :thumbup:
 
#20 · (Edited)
norcal 528i said:
I am just glad that other people find the ABS in these cars a bit eccentric.
I wouldn't exactly call it eccentric. I would call it confused.

Also, another attribute of the ABS problem is the humming that is heard while the system is working. So the shudder in the front that you can feel along with the humming that you can hear together collaborate to make you think that your car is about to fall apart on the spot.
 
#21 ·
dagoo98 said:
The fact that you brake and go over a bump should first clue you in on the fact that it most likely is your ABS kicking in.
I (and I assume other posters who have had similar problems) currently own and have owned other ABS equipped cars and have not experienced this problem with others. Why I should assume ABS is beyond me. Only because it seems recurrent amongst others am I inclined to think design of car and its systems, hence ABS.
 
#22 ·
LA525iT said:
I (and I assume other posters who have had similar problems) currently own and have owned other ABS equipped cars and have not experienced this problem with others. Why I should assume ABS is beyond me. Only because it seems recurrent amongst others am I inclined to think design of car and its systems, hence ABS.
I have experienced the speed bump problem in my old Land Rover. I guess it would be safe to presume that for a split second while the car is rebounding from the speed bump and the brake is pressed hard enough that a momentary instance of lockup is detected by the ABS sensors and begin to cycle the brakes.

The ABS sensors on all these cars are quick and are capable of picking up several hundred actions per second so I don't think it takes more than a momentary lockup to kick the system in.

To me, when this happens I consider it more of an annoyance than anything else. It's one of the only downsides to ABS I can think of.
 
#23 ·
dagoo98 said:
My reply was constructive, the scenario you described are exact symptoms of warped rotors. Remember that the people on this forum cannot drive the car to tell themselves so they go by your descriptions. When a car has warped rotors, when you apply brakes at highway speed, 50mph and above, the steering wheel shakes from left to right and you feel the vibration in the front of your car until you let go of the brakes.

The fact that you brake and go over a bump should first clue you in on the fact that it most likely is your ABS kicking in. It also will not stop until you release the brake because that is what is designed to do, the whole purpose is to prevent the brakes from locking up and causing an unsafe condition. It forces the driver to release the brake and re-engage the brakes which ensures that the brakes will not lock up because of the bumps in the road. I simply was trying to explain that it was either your rotors being warped or your ABS kicking in, not quite sure how that's destructive.

I don't understand when people post here looking for answers and then get offended when others offer answers. :confused:

Thank you norcal 528i for understanding the intentions of my reply. :thumbup:
I am sorry if I misinterpreted your reply, but it sounded a bit arrogant when I read it.

In regards to ABS, everything I have been taught (which had to undo my years of training without ABS) is that you are to stand on the brakes once ABS activates (there are plenty of publications that tell you this), which is not what we used to do when the tires started to lock up (which was to release pressure or pump the brakes to the point that lockup was averted). This is now contrary to what you are telling me to do, release the brakes so it can reset itself and reapply, which increases my braking distance.

I personally find the ABS system when activated over a bump unsafe in both the E39 and E38, and to require brake release by the operator to stop the car from doing it's own unnecessary and uncoordinated dance a hazard in the fact that stopping distance is exaggerated rather than reduced and controlled.

I have felt the e39 actuate the ABS system when the ground is slick, and it is nothing like when a bump is hit and it actuates. Under "normal" conditions of activation, it works great.

My past cars when hitting bumps while braking have activated the ABS system, but never with such nervousness and sense of uncontrollability the E39 has, those other cars also self corrected themselves without hesitation or interaction of the driver (just constant pressure as they have taught us with ABS).

I am sorry, but while I firmly believe in ABS, the system in the e39 is flawed in its execution over bumpy roads. For some reason the system becomes confused and can not reset it self, but instead sends itself into a violent frenzy instead of a controlled response like it exhibits on slick (but smooth) surfaces. When this wild sensation occurs, it is usually on dry surfaces, but with a bump or two on one side of the car, such a condition is common and calls for a controlled response, not what the E39 demonstrates.

While I am not trying to get into a "contest" with you, I am surprised that you have not seen more controlled responses in ABS systems used in other cars, could it be that you have not driven any other cars other than a BMW (j/k)?

With all the other cars I have owned with ABS and the multitude of rental cars I have driven with ABS (and I certainly like to give the rentals the "breakfast, lunch, and dinner" treatment, with the adage, "don't be gentile, it's a rental" branded into my head), I have never seen a car with such nervousness when ABS is actuated due to a bump on "dry" pavement, based on this, I begin to question if the system really is right, since it supposed to improve safety, not decrease it (what I believe it does in this situation).

Based on the responses to the original post, and some of mine, I think others may be in my camp.

All in all, I think the ABS systems by other manufacturers offer a higher level of control and composure than the E39 and E38 due to the reaction of the system over bumps.

I am not flaming, just telling you my opinion of the system based on the years of driving experience that I have, both with and without ABS systems.
 
#24 · (Edited)
OK, so I feel I am an unfortunate expert with this subject.

First off, this is not ABS normal working. This is ABS malfuntioning if at all.

Anybody with this problem knows how an ABS feels like when it engages. This does not feel the same.

Believe me when I tell you, one month after buying my E39 this symptom surprised me when I came to a red light. I was about 40'-50' away, driving normal city speed. The car did not even slowed down. Right into the butt of the car that was standing at the red light. $3500 damage on my car. $1500 on his car.

Since then, almost 3 crashes into the rear end of cars in front of me.

Fact: it will usually happen in a slow speed. 3-5 mph. The vibration is much faster then the pulsating speed of ABS working correctly.

cure: replaced shocks and struts on front and rear ends. Replaced wheels from 16" to 17" two weeks later. Since then, sysmptom almost completely dissapeared.

I have a theory of exactly how this happens. but it is way too long to explain in writing. But it has to do with a "positive feedback loop" between wheel bouncing to the air, while abs activates at the wrong time, landing on the road just to bounce again and to activate abs again while in the air. It causes harmonic oscilation that will not stop because it continues to feed itsef infinitly.

Not ABS, you can stop a car with ABS activated.
Not wraped rotors. Wraped rotors vibrates the steering wheel in high speed braking.

This symptom, happends in slow speed. Vibrate the front wheels (bouncing), and the car will NOT stop.

Of course, anybody who did not experience this first hand will think we don't know what we are talking about and we don't know how ABS feels.

Hope it is a little more clear now.

Is that fairly describs what you guys experiencing?
 
#104 · (Edited)
E39 ABS Issues



I was pleased to learn today that I have not lost my mind. In the past 2 months, I have hit the same pot hole in LA in my 2003 530i MSport and thought the front end was coming off. I have driven ABS before in an S70 Volvo previously so knew the drill to just stand on the brake and let it work as the dealer and manual state. I have been driving since 1972 and have never had an accident until today. While driving to work on the 110 freeway, I merged into the flow of traffic still in 3rd gear from the ramp as the right lane ahead was merging into my lane as that lane was ending. Another car in the right lane was running out of room and cut in front of the Toyota 4Runner ahead of me which immediately braked hard and in turn, I hit the brakes hard at about 45 mph. The violent shuddering began but the car would not stop as I stood on the brake as hard as I could with the clutch in and it felt like sliding on ice as the car slowed to about 15 mph and hit the trailer hitch dead on the kidney grill and into the new radiator I had just paid for at the dealer not 15 minutes prior. To say that experienced drivers do not understand ABS is an oversimplification. I was not distracted, did not have the radio on and was not on a cell phone, yet I could not stop the car. Fortuantely, no one was hurt and I was able to get off the road and have a flat bed pick it up. The repair bill is close to $5,000 and my insurance company says I am at fault certainly for a rear end collision.

I have owned BMW's since my first 2002tii but all that safety engineering could not avert what should have been an avoidable accident. How many of you who have experienced this have filed a report with the NTSB? Has BMW ever ackowledged this as a problem?
 
#216 · (Edited)
There are many new people on this board and this thread is very old, and long. So for the benefit of renewing the information, here is what I said starting at 2004. It still hold true. I picked only the more informative posts. It seems that some who fiercely argued and disagreed with my analysis have come around to actually repeat my explanation, although not so accurately. So for that reason, here goes. Please read. Understand, and take care of the problem.

12-17-2004, 11:25 PM:
OK, so I feel I am an unfortunate expert with this subject.

First off, this is not ABS normal working. This is ABS malfunctioning if at all.

Anybody with this problem knows how an ABS feels like when it engages. This does not feel the same.

Believe me when I tell you, one month after buying my E39 this symptom surprised me when I came to a red light. I was about 40'-50' away, driving normal city speed. The car did not even slowed down. Right into the butt of the car that was standing at the red light. $3500 damage on my car. $1500 on his car.

Since then, almost 3 crashes into the rear end of cars in front of me.

Fact: it will usually happen in a slow speed. 3-5 mph. The vibration is much faster then the pulsating speed of ABS working correctly.

cure: replaced shocks and struts on front and rear ends. I also replaced wheels from 16" to 17" two weeks later. Since then, symptom almost completely disappeared. (Edit, 9/14/09: It was actually gone forever, I just didn't know it at that time yet.)

I have a theory of exactly how this happens. but it is way too long to explain in writing. (9/14/09 Edit: I am explaining it later in this post.) But it has to do with a "positive feedback loop" between wheel bouncing to the air, while abs activates at the wrong time, landing on the road just to bounce again and to activate abs again while in the air. It causes harmonic oscillation that will not stop because it continues to feed itself infinitely.

Not ABS, you can stop a car with ABS activated.
Not warped rotors. Warped rotors vibrates the steering wheel in high speed braking.

This symptom, happens in slow speed. Vibrate the front wheels (bouncing), and the car will NOT stop.

Of course, anybody who did not experience this first hand will think we don't know what we are talking about and we don't know how ABS feels.

Hope it is a little more clear now.

Is that fairly describes what you guys experiencing?
12-19-2004, 07:47 AM
12-18-2004, 12:30 PM
Interesting explanation. How fast were you driving when the first crash happened? In my case it's never happened at speed more than 3-5 miles per hour, like you said, so besides the annoyance I've never really considered it to be a safety concern. If this condition happens at speeds greater than 5 miles I'd be concerned. Can you elaborate a little more about that crash that you had? Thanks.
When the first crash happened I was driving around 30mph, you know, just normal lazy driving from one traffic light to the next one. We were the only two cars at that stop. I started to stop at normal distance, the front started to vibrate. Since I was 'new' to the car, I didn't understand what was happening thought that is the ABS and that it will stop, but the car continued and 20' away I realized something is very wrong and I can't stop the car. I pressed the brakes as hard as I could, the car didn't even slowed down. Crashed right into that guy in front of me. I now know that if it happens you should quickly release the brake pedal and re-apply the brakes. This is THE one reason I would not let anybody drive my car, by the way! In most other times it just when speed is very slow, so you have time to react.

At other times it was just crawling in heavy city (NYC) traffic when you drive bumper to bumper. You are closing a gap of 15' to the car in front of you, and this happens when you are 5-8' away... now you are in BIG trouble, right?... LOL. Only the experience from the past teaches you to quickly react by releasing the brakes and re-applying. Very scary.

This is definitely a safety issue, IMO.
12-19-2004, 08:39 AM
Is it possible that your front shocks are gone already? Stock shocks are by Sachs. (I think the sport package also by Sachs.) But they don't last forever. I went to a few dealers and few other shops and told them I suspect my shocks are gone. They all told me that my shocks are good. One dealer mechanic even took it to a road test with me. Another SA took it with me to demonstrate ABS... :) I don't know of any way to measure shocks effectiveness. Its all subjective and comes down to "feel".

When I finally replaced the shocks, the technician was 'shocked' at their condition, :) The front shocks were so gone that I could compress them completely or pull them out easily with just two fingers!

If you have this problem on your car, then most likely you have bumpy roads where you usually drive, and chances are, your shocks worn out faster. Just like mine.

The contribution of the shocks to this problem is that they do not suspend/dampen the spring vibrations. The contribution of the wheel size is in its weight and tire wall height, which will affect the frequency of the 'bounciness'. My thought was that since I thought of this as a feedback, I wanted to break the cycle by changing the "oscillation frequency"...

I think replacing the shocks had more to do with curing this problem on my car then size of the wheels. How many miles do you have on your shocks?
12-19-2004, 09:04 AM
KarlB, thats pretty much what I am thinking.

Here is my theory of how this happens:

1. I am braking at a speed that should not activate ABS. No wheel locking.

2. Front wheel hit a bump, and bounce to the air.

3. Since the wheel is in the air, it will now lock because there is no resistance. (the weight of the car does not push the wheel forward against the pressure of the brakes, so that wheel will easily lock.)

4. ABS will notice that one wheel is not turning, while the others do turn. Therefore mistakenly thinking that this wheel is sliding on the road!

5. ABS will start pulsating the brakes, in harmony with the bouncing rate of the wheels, therefore causing them to continue bouncing, just for the ABS to continue thinking they are locked.

TXE39, you said you have it on your Land Rover. I heard BMW owns Land Rover... ??? Just like they own, Mini, and RR.

You know that story of the soldiers marching on a bridge and the pace of their steps matched the "oscillating frequency" of the bridge. The frequency feed on itself vibrating the bridge so much that it destroyed the bridge.

I think that is what happening on our E39s. The cure is to change the frequency or to prevent it from even developing (shocks).

Any other thoughts/theories out there?

Oh, and I didn't have almost 3 crashes. I meant to say I had a "almost a crash" about three times since that ONE crash... :D
07-17-2007, 12:29 AM
I actually had to pleasure of crashing my car into the rear of the car in front of me when that happened to me the first time. $3,500 damage.

Then I almost crashed into a rear of a 24' truck a few months later, and a few other close calls. I just learned that I have to let go of the brakes, and reapply the brakes quickly before I hit something.

And it was not the rubber bushing.

All the control arms were replaced, and it happened again, just not as often. Then I decided to replace the shocks. After replacing the shocks, the problem was gone. That was 60,000 miles ago and it never happened again.
(EDIT, 9/14/09: it is now more then 2 years later (meaning total 5 years), and still, it NEVER happened again. Problem solved. Gone.)

Checking the old shocks after they were out, they were completely gone. There was no resistance left in them. Zero. You could completely compress them while holding he rod between your two fingers.
09-30-2007, 01:48 PM
If you are still experiencing this. Fix it ASAP. Go to a good BMW tech, and have them look at the front suspension and fix/replace anything that is worn out - meaning, the obvious noticeable wear. If after that you still have the problem, than replace your shocks.

Good shock absorbers will STOP the 'bouncing'. Shut shocks = you are riding on springs. The car will bounce like a basketball.

Again, fix it ASAP. You can kill yourself or somebody else. Seriously.

.
09-30-2007, 02:27 PM
So, someone on this thread earlier was talking about "harmonic oscillations".. not exactly the right description but good enough. If we think back to elementary diff eq. or physics, we would remember that you can never have harmonic oscillation in a system with any sort of damping, so logically the damping must be at fault (which it was).. Combine this with the fact that any fault in DSC/ABS is highly unlikely, and you have found your culprit..

Don't know why you guys got into this big discussion about driving styles a couple years ago, when if you just sat down and thought about it you would have found out the answer.
(This guy finally got it! )

10-04-2007, 08:08 PM
Exactly! You got it! That is exactly what I am explaining!

That was my post. Paying $3500, having my insurance go up, and almost killing myself on another occasion, made me very passionate about this issue.

I said a few times in this thread, that this is dangerous. Just a few days ago I told someone on this thread to fix it before he could kill someone or himself.

***8230;. and guess what. Just yesterday, Splooge had an accident. Just like the one I described.

Sorry about your car, Splooge.

.
So... I started posting about this in 2004. I explained then and I will repeat again: YOU NEED TO REPLACE YOUR SHOCKS. Some argued with me that replacing the rubber bushing is the solution, but if you will read the whole thread, you will see that bushing did not solve the problem, or solved it only temporarily. The problem came back rather quickly. ONLY after replacing the struts/shocks the problem was gone. Mine is gone for 5 years already, never to return, EVEN when my bushing were shot.

More so, having this problem IS an INDICATION that your struts/shocks are gone. Even if you stopped the shuddering with the bushing, YOUR SHOCKS ARE STILL GONE.

Replacing struts/shocks may look expensive. But fixing your car after a crash costs even more. And you could kill yourself too.

mw
 
#25 ·
Matwiz, yes very similar, but car was able to stop (not well, but it did stop). Interesting explination. Only thing, both cars have sport package (so larger wheels) and one is very low milage, other is up there, both have it. I would agree on the feedback loop.
 
#26 ·
MatWiz said:
OK, so I feel I am an unfortunate expert with this subject.

First off, this is not ABS normal working. This is ABS malfuntioning it at all.

Anybody with this problem knows how an ABS feels like when it engages. This does not feel the same.

Believe me when I tell you, one month after buying my E39 this symptom surprised me when I came to a red light. I was about 40'-50' away, driving normal city speed. The car did not even slowed down. Right into the butt of the car that was standing at the red light. $3500 damage on my car. $1500 on his car.

Since then, almost 3 crashes into the rear end of cars in front of me.

Fact: it will usually happen in a slow speed. 3-5 mph. The vibration is much faster then the pulsating speed of ABS working correctly.

cure: replaced shocks and struts on front and rear ends. Replaced wheels from 16" to 17" two weeks later. Since then, sysmptom almost completely dissapeared.

I have a theory of exactly how this happens. but it is way too long to explain in writing. But it has to do with a "positive feedback loop" between wheel bouncing to the air, while abs activates at the wrong time, landing on the road just to bounce again and to activate abs again while in the air. It causes harmonic oscilation that will not stop because it continues to feed itsef infinitly.

Not ABS, you can stop a car with ABS activated.
Not wraped rotors. Wraped rotors vibrates the steering wheel in high speed braking.

This symptom, happends in slow speed. Vibrate the front wheels (bouncing), and the car will NOT stop.

Of course, anybody who did not experience this first hand will think we don't know what we are talking about and we don't know how ABS feels.

Hope it is a little more clear now.

Is that fairly describs what you guys experiencing?
Interesting explanation. How fast were you driving when the first crash happened? In my case it's never happened at speed more than 3-5 miles per hour, like you said, so besides the annoyance I've never really considered it to be a safety concern. If this condition happens at speeds greater than 5 miles I'd be concerned. Can you elaborate a little more about that crash that you had? Thanks.
 
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