klaus Posted January 27, 2006 Share Posted January 27, 2006 Hi, I was going from a parking lot to the street downhill through a 30ft long back alley today. When I touched the breaks, they rattled for a moment... On a dry pavement at below 10 miles per hour... Kind of a like the ABS... A couple of weeks ago I had a similar experience in a garage going down 5 levels. Again low speed and dry concrete in this case. Each time it lasted only about a second or two and then everything was back to normal... Both times the downhill was steeper than average, but not extremely steep. Any guesses on what's going on? I don't think it makes much sense going to a dealer because it's nearly impossible to reproduce (I tried). Thanks, klaus. Link to comment Share on other sites More sharing options...
eL GaTo Posted January 27, 2006 Share Posted January 27, 2006 http://legacygt.com/forums/showthread.php?t=8911&highlight=brake+shakes Are you sure it is "rattle" of "shake"? Check this thread. "Remember..."MODDING is a HOBBY:icon_bigg, not a BAAAD HABIT";) . Link to comment Share on other sites More sharing options...
Fast Wagon Posted January 27, 2006 Share Posted January 27, 2006 It is most likely rust on the rotors that forms when the pads sit on the rotors for a while is wet weather on when you wash your car and do not drive it afterward. Once you apply the brakes after the cars been sitting, the rotor gets clean/smooth again after a few rotations with the brakes applied. Its normal. Link to comment Share on other sites More sharing options...
Desmond Posted January 27, 2006 Share Posted January 27, 2006 I have the same problem too, and like you said cannot consistently reproduces this, however, you are right it when it happens I am on a downhill slope, but not reproduceable. I do not think it is rust..... Hope someone can shed some light on this..... Thanks Link to comment Share on other sites More sharing options...
magnetic1 Posted January 27, 2006 Share Posted January 27, 2006 Did they "rattle"? or just feel rough? Free Sonax Cleaner Deal http://www.brakeswap.com Carbotech, Hawk, PFC, DBA Rotors, Motul, Wilwood, Castrol... Great service. No bumping required ! Link to comment Share on other sites More sharing options...
klaus Posted January 27, 2006 Author Share Posted January 27, 2006 http://legacygt.com/forums/showthread.php?t=8911&highlight=brake+shakes Are you sure it is "rattle" of "shake"? Check this thread. Nope, completely different -- very slow speed and downhill. And it rattles, does not shake the steering wheel or something. I felt it on the pedal. Similar to when ABS would kick in (which would make no sense considering other circumstances). It is most likely rust on the rotors that forms when the pads sit on the rotors for a while is wet weather on when you wash your car and do not drive it afterward. Once you apply the brakes after the cars been sitting, the rotor gets clean/smooth again after a few rotations with the brakes applied. Its normal. Yesterday the roads were dry, so no water was around and the car was sitting for just about over an hour. This car is driven daily several times. The first time it was in a garage after the car was sitting there for about 8 hours. I have the same problem too, and like you said cannot consistently reproduces this, however, you are right it when it happens I am on a downhill slope, but not reproduceable. I do not think it is rust..... Hope someone can shed some light on this..... Thanks Agreed -- it does not feel like rust... it feels more like ABS kicking in, but this makes no sense either. Link to comment Share on other sites More sharing options...
j255c Posted January 28, 2006 Share Posted January 28, 2006 mine were especially rattly, shaky tonight as well. 06 TB EVO IX SE stock turbo monster subaru hater Link to comment Share on other sites More sharing options...
laz Posted January 28, 2006 Share Posted January 28, 2006 If you are going downhill an in a circle there may be a point in time when one wheel is spinning faster than the other while braking? Just a thought. --- Link to comment Share on other sites More sharing options...
klaus Posted January 28, 2006 Author Share Posted January 28, 2006 If you are going downhill an in a circle there may be a point in time when one wheel is spinning faster than the other while braking? Just a thought. Sure, it was in a turn... However, this is still normal operation... I'm not sure what you mean...? Link to comment Share on other sites More sharing options...
laz Posted January 29, 2006 Share Posted January 29, 2006 Just thinking that while braking downhill in a circle the ABS sensors may mistake one wheel turning faster than the other as skidding and activate. I know mine activate sometimes in the weirdest places, like going over train tracks while braking, or speed bumps. Just a thought. X --- Link to comment Share on other sites More sharing options...
SBT Posted January 29, 2006 Share Posted January 29, 2006 I was thinking the same thing...steep, decreasing radius turn one wheel moving faster than the other and the ABS momentarily kicks in to equalize speeds. Given how steep some of these exits are, ABS kick-in seems reasonable, especially since your angle sensors and weight shift sensors would be at the maximum braking thresholds. How long does the ABS-feel last? Can you hear anything, such as the ABS servo pump or is it just the sense that the ABS is coming on? SBT - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
mwiener2 Posted January 29, 2006 Share Posted January 29, 2006 Could also be the ABS doing a self cehck My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
klaus Posted January 30, 2006 Author Share Posted January 30, 2006 Interesting... The rattles lasted max a couple of seconds, if even that long. It's a noisy rattle or "buzzer" and it is also felt on the brake pedal... I would think that going downhill in a turn, although somewhat steeper, is perfectly normal and ABS should ignore it (especially with the VDC)... Link to comment Share on other sites More sharing options...
mwiener2 Posted January 30, 2006 Share Posted January 30, 2006 could also be your wheel fallling off My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
SBT Posted January 30, 2006 Share Posted January 30, 2006 If the pedal is pulsing (buzzer-ing I think is how you described it), that's a sure indication that your ABS is lighting off. Now that you mention it, the VDC may be the actual contributor to this as I mentioned before, angle and weight shift sensors are much more attuned/present in the VDC setup. And the noisy "rattle" that you describe certainly describes the sound of an ABS servor pump when it cycles. Is there any kind of a stuccato, rapid sound on/off, on/off with this occurence? Does the pulsing stop as soon as you release the brakes? Perhaps attempting this down exit at different speeds (within the margin of safety of course) would enable you to and see if there is any change (lack of noise, pulsing, buzzing, etc.). If the pulsing lasts longer, then it is likely the ABS is cycling which given the comments above, would seem like it's doing its job and I wouldn't worry about it. If the pulsing/noise stops all together, then it's likely that the wheels are turning fast enough for the sensors not to pick up the change, side to side and not cycle the ABS. Maybe, you're right in that mid-zone where the ABS has a choice and quickly cycles. Let us know what you find and/or how you resolve. SBT - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
klaus Posted January 30, 2006 Author Share Posted January 30, 2006 If the pedal is pulsing (buzzer-ing I think is how you described it), that's a sure indication that your ABS is lighting off. Now that you mention it, the VDC may be the actual contributor to this as I mentioned before, angle and weight shift sensors are much more attuned/present in the VDC setup. And the noisy "rattle" that you describe certainly describes the sound of an ABS servor pump when it cycles. Is there any kind of a stuccato, rapid sound on/off, on/off with this occurence? Yeah, I was thinking about the VDC after I posted my previous message... Going downhill, accelerating (gravity), breaking and turning at the same time could result in an interesting situation... If the nose is trying to escape, I would expect the VDC to kick in and try to steer it. I haven't checked if the VDC light came on... I'll play a bit with this and see if this thing is somewhat predictable... Thanks for ideas... klaus. Link to comment Share on other sites More sharing options...
klaus Posted January 30, 2006 Author Share Posted January 30, 2006 could also be your wheel fallling off Well, this would not be good... But, no, I don't think it's falling off -- they've been retorqued about 3 weeks ago Link to comment Share on other sites More sharing options...
Desmond Posted February 2, 2006 Share Posted February 2, 2006 Hi Klaus, I also get under heavy breaking (emergency), grinding in the brakes similar to worn brake pads grinding into the disks... (I only have 8000km on my car so the pads should still be "new" Again, this does not happen all the time...... and cannot be reproduced. I sense that this may be related to your reported rattle problem. Strange that so few persons have reported the rattle problem. If you have more info, please keep me posted. Thanks Desmond Link to comment Share on other sites More sharing options...
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