Author Topic: W8 Passat owners  (Read 2001 times)

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cooky

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W8 Passat owners
« on: January 10, 2007, 08:24:56 PM »
Hi all-

This is my first post on RMCB5.  :)  'm looking for any W8 Passat owners in the Denver area.  Please raise your hands!  ;)

I recently got a W8 and I have a question concerning my ABS - wondering if I can take a poll on the following:

On snowy/icy/slippery conditions, when the ABS engages, do you hear a gawd-awful grinding noise like there are rocks between your pads and rotors?

The dealer is telling me this is normal, but my Jetta never made that sound, nor does our other truck that has ABS (for that matter my Saab or Toyota didn't either!).  It's hard for me to believe that this noise is normal, considering the mindfulness of German engineering.  On the other hand, I know W8s have four pads/wheel, so maybe the sound is exacerbated by this?

Have any W8 owners experienced this?

Thanks for your help!

03Indigo

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Re: W8 Passat owners
« Reply #1 on: January 10, 2007, 08:30:22 PM »
I don't have a W8...but I heard the same noise on my 2 1.8T Passat, and on my allroad....so I guess it IS normal.

I have heard it on my wife's tacoma, and on my Subaru....it is the pulsing of the ABS.

FYI....my allroad has the same HP2 calipers up front that your W8 has....and I don't think the number of pads or pistons makes much difference in the function of the ABS....but maybe in the performance.

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Re: W8 Passat owners
« Reply #1 on: January 10, 2007, 08:30:22 PM »

hotani

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Re: W8 Passat owners
« Reply #2 on: January 10, 2007, 08:38:16 PM »
I think it is simulated feedback so you can 'feel' that the ABS is engaging. Some cars do it without letting you know. I guess VW/Audi wanted to provide a more engaging driver experience than those other guys. ;)
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92UrS4

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Re: W8 Passat owners
« Reply #3 on: January 10, 2007, 08:43:04 PM »
I had a 2000 A6 2.7T which, like Jon mentioned had the HP2's I believe. Nice heavy duty setup. I did hear some grinding type noises under heavy braking. After some discussions with a local dealer, I too was told it was normal. The other thing to keep in mind is some cities still toss gravel on the roads in these storms.

So you can get some crud up in there and you will hear some grindage under braking.

By the way, welcome to RMCB5, hopefully we will get to see you and your W8 at a GTG sometime.

cooky

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Re: W8 Passat owners
« Reply #4 on: January 10, 2007, 08:57:46 PM »
Thanks, guys!   :)

It's an engaging driving experience alright - it scared the crap out of me when it first happened!

Like I said, this is the first car I've had that makes that terrible noise, so I wanted to open it up to the masses to see if I was crazy.   :?

And, just because I'm such a n00b, what is a GTG?   :oops:

92UrS4

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Re: W8 Passat owners
« Reply #5 on: January 10, 2007, 09:01:44 PM »
GTG = Get Together, be it a garage day, burgers n beers or a all VW community meet.

Also, one thing to note, that W8 of yours is one heavy beast, so you can't throw it around like a Golf or even a Jetta. It has the heavier duty brakes for a reason. This could also be a factor in your experience.

It is a great car and as the roads clear up and we finish up this wintery season you'll have a lot more fun with it and get to know it a lot better.

cooky

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Re: W8 Passat owners
« Reply #6 on: January 10, 2007, 09:13:45 PM »
Okay, cool!  :)  I see there's one on the 21st.  Going to try and make it to that.

hotani

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Re: W8 Passat owners
« Reply #7 on: January 10, 2007, 09:45:15 PM »
Come to think of it... When I was driving in heavy snow over rabbit ears around the first of December, I heard some grinding on the brakes that had nothing to do with ABS. I am pretty sure there was ice build-up on the rotors, pads or both since every time I would apply the brakes it would sound like grinding metal. It went away later, and I'm assuming it was ice that finally melted off the parts once the car entered a lower, warmer elevation.
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Cole

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Re: W8 Passat owners
« Reply #8 on: January 10, 2007, 09:47:41 PM »
As long as we are on the topic. Here are a few thoughts on ABS.


The system was never designed to stop a car quicker. It was designed to give you some traction to allow the car to steer under heavy breaking. You can actually stop a car faster by braking as hard and fast as you can WITHOUT activating the ABS.

Braking up to the "threshold" will give you the most effective stopping power.  Once you cross the "threshold" and a wheel locks up the ABS RELEASES brake pressure to get the wheel spinning again. If you have your foot planted firmly on the brake pedal you will cross the threshold again almost instantly causing lockup agian. This causes the ABS to release pressure agian. The pulsing/grining/etc that you hear/feel in the car is the ABS system releasing pressure from the system. The only way to add pressure is with your foot on the pedal.

Different cars run different systems. Some have a 3 way system and some a 4 way. The 3 way releases the front tires independently and the rears as a set. This can be extra bad since it is releasing pressure on a wheel that may have perfect traction. While the 4 way system is better by doing each wheel independently. Most of these systems still run a full "cycle" every time they sense one wheel lockup. Which means that all four get pressure released even if they don't need it.

Since each vehicle behaves differently you will get a different feel from the pedal. Most systems do not work under 7-10 mph. Above that and they sense lockup differently and the response time can be different based on tires, brakes, brake pads, shocks, suspension etc. So the grinding in the W8 could be perfectly normal for your current set up. A simple change in tires could make the system seem smoother.

ABS is a great system for people that don't get threshold braking or as a back up to your own skill.

We use to demostrate this to students on a skid pad. On the slick surface we could consistantly stop a car from 20mph in  2-3 car lengths SHORTER distance by threshold braking the car VS. just letting the ABS do its thing.


 :D

Cole Ford
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ianacole

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Re: W8 Passat owners
« Reply #9 on: January 10, 2007, 10:02:49 PM »
To your point about turning Cole, there was a good demonstration of the effective turning distance under hard braking that I saw online somewhere - I'll see if I can find it.  Basically, without ABS, turning under hard braking induced huge amounts of understeer causing the car to plow straight ahead, whereas the ABS enabled the car to turn.
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cooky

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Re: W8 Passat owners
« Reply #10 on: January 10, 2007, 11:18:57 PM »
Interesting - I guess if I changed my tires to snow tires, or maybe a higher-performance all-season, I'd get better traction, so my wheels wouldn't slip as easily, therefore less need for ABS to engage.
 
I just recently learned about threshold braking - totally makes sense to me, but it's hard to fight the urge to just press the pedal constantly when you're in an emergency situation.  Especially since the ABS people say "DON'T LET UP PRESSURE ON THE PEDAL".  The weird thing is that I can be going 5mph, or just idling along with my foot off the accelerator, but if I slam the pedal, it'll grind.

To hotani's point - I grew up in the northeast (freezing rain central) and I'd sometimes have a layer of ice on the pad, like you described and it caused a grinding noise.  It always went away after a few gentle braking sessions, however.

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Re: W8 Passat owners
« Reply #11 on: February 05, 2007, 02:15:31 AM »
It has been a long while since I have posted, and noticed your post on the W8.  I completely agree with the comments others have made, and I have also experienced similar ABS performance as you have.  There have been some ABS controllers in the W8 that were defective and replaced by VW for the reason you have mentioned.  However, I never did any research on the subject so I am not sure if you could have one of these defective units.  

In general, I have been told that ABS systems perform at 95% of theroretical maximum braking capactiy.  If you were to disable an ABS system and had significant experience and traning, you could probably outbrake an ABS system in any condition.  The intent of ABS is to provide the average driver with control when braking and turning even if that driver were to apply maximum braking force at the wrong time.  It works well for its purpose.  

I probably havn't offered anything of value, but I would check with a VW delear to see if your VIN falls under any sort of TSB for defective ABS controllers.  Otherwise, it is probably related to tires and the conditons at that time.

Good luck!

Jason
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