E46 front end wobble

Just today my car (2001 330 ci sport) started wobbling in the front end while braking from 40 mph+. The tires and wheels are fine. Any probable cause? A place for me to start? TIA

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sgfan3 wrote:

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Hmmm... hadn't considered that. Any other possibilities? Worn parts like tie-rods, control arm bushings, steering box?

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Worn parts would manifest themselves under other conditions. If the shaking is limited to braking, the most likely cause is the rotors.
The brake pads get thin and do not disipate the heat as well as they should, and the rotors can warp. If you did a hard stop that got the rotors hot, then went into a puddle, the heat shock could cause warping. In any case, you can get new rotors for about $50 each and they are easy to install at home.

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Warped brake rotors can cause this.

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My bet: a front brake caliper is seizing.
This is pretty common. The front calipers slide back and forth on metal rods; any dirt or corrosion on the rods and the caliper seizes, then when it gets hot it gets VERY grabby.
Next time this happens, stop the car, get out, and sniff near each wheel. If you get a strong odor of brake dust that's a big clue. (You might also notice that one wheel is getting MUCH dirtier than the others). You can also CAREFULLY touch each wheel - one might be significantly hotter than the rest.
If it's under warranty, then BMW replaces that caliper, the pads, and the rotor, and then fills and bleeds the fluid.
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That sounds like a possibility. I'll check the calipers tomorrow and let you know what I find.

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I don'tthink there is anything wrong with the calipers, the rotors are the suspect to be looking at.

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Just "re-discovered" this thread and have an update. The wobble in the front was caused by loose lug nuts (RF). I was so focused on finding another, more complicated solution, that I hadn't considered the most obvious and simplest fix. Fortunately, no harm was done while the nuts were loose, but this incident has made me more aware (again) of the importance of the driving experience. Proper maintenance, quick inspections (and corrections while still relatively inexpensive) of the simple things as well as the hi-tech, high-dollar stuff we worry about. In exchange, your BMW will reward you with a great deal of driving pleasure, instead of trip after trip to the garage. Then there is the withdrawal and inconvenience of it all. This is all part of my quality of life. M3 forever!!! Lug nuts! Who knew!
sgfan
...feelin' kind of silly right about now...
seizing.<BR>&gt; &gt;&gt;<BR>&gt; &gt;&gt; This is pretty common. The front calipers slide back and forth on metal<BR>&gt; &gt;&gt; rods; any dirt or corrosion on the rods and the caliper seizes, then<BR>&gt; &gt;&gt; when it gets hot it gets VERY grabby.<BR>&gt; &gt;&gt;<BR>&gt; &gt;&gt; Next time this happens, stop the car, get out, and sniff near each<BR>&gt; &gt;&gt; wheel. If you get a strong odor of brake dust that's a big clue. (You<BR>&gt; &gt;&gt; might also notice that one wheel is getting MUCH dirtier than the<BR>&gt; &gt;&gt; others). You can also CAREFULLY touch each wheel - one might be<BR>&gt; &gt;&gt; significantly hotter than the rest.<BR>&gt; &gt;&gt;<BR>&gt; &gt;&gt; If it's under warranty, then BMW replaces that caliper, the pads, and<BR>&gt; &gt;&gt; the rotor, and then fills and bleeds the fluid.<BR>&gt; &gt;&gt;<BR>&gt; &gt;<BR>&gt; &gt; <BR>&gt; </FONT></BODY></HTML> ------=
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