Can old eccentric bolts and washers and/or (mis-) alignment cause passenger front wheel shimmy under aggressive braking?

Background: I’ve owned my 2011 Panamera Turbo for 8 years now, 155K miles. It’s a wonderful ride, but there has been one thing that has always been annoying; during aggressive braking from speeds 85+, the passenger side wheel has a shimmy, which disappears around 60mph. This has been (and is) the case through years of DIY of 2 new sets of rotors and hawk pads, brake bleeding, replacement of air struts, steering ball joints, upper and lower control arms, PDCC front sway bar links and bushings. I’ve gone through several sets of tires and many balances, so it’s not a wheel balance issue. Tire people tell me the wheels are straight.

The shimmy was not as prevalent, but definitely still there, after control arm replacement and wheel alignment; 6 months later, it was just as bad as it had ever been. I believe the only thing I haven’t replaced is the lower control arms Eccentric bolts and washers. The car has never been in an accident. I’m under the car often and have not discovered any signs of an accident damage. Can old eccentric bolts and washers and/or alignment cause a passenger front wheel shimmy under aggressive braking? Is there a good suspension Indy on the CA Central Coast? I've always avoided the Dealer. Maybe I shouldn't.

I’m interested in experiences that resolved high speed braking issues on a 2011 970.

 

Check or have someone rebleed the brake system, then check the tire pressure.

 

That's worth a try, thanks.

 

11 turbo 67k
no issues until cv boots needed replacement, and now I'm experiencing similar issues with no solution in sight.

 

I'd check your brakes, check the rotors for hot spots or warping, brake pads for uneven ware, then check the tread on your tires for weird flat or cupping. From there bring it to a professional brake service place to rebleed the brake system.

 

The only thing not mentioned as changed already is wheel bearing. That could also be in play but I would expect some noise or other symptoms. Do the usual hard turn left to right driving tests and see if you can pick up something at low speed. I've had a wheel bearing be noisy and have zero play but never no noise with any kind of play. Its possible the speed matters here too. My 2 cents.

 

Wheel bearings is the expensive repair... That's why I didn't mention it, the rule of thumb is to check out the cheap fixes first.
But yes if you can lift the car up and spin the wheel freely if you hear a grinding sound could be your wheel bearings.

 

Rust between the hub and rotor is my first bet; or just some sort of imperfection where the rotor meets the hub.

sometimes the wheel mounting surface itself, where it meets the rotor, can also accumulate crap, and it not cleaned every time a job is done (tire, brake, hub, usw) oscillations can appear in specific speed regions.

my question is whether hard braking pulls to one side.
also just whether you're tried a cheap runout measuring tool, usually good enough to detect something as maddening as what you've been experiencing. these steel rotors are hard to warp, and with everything being replaced it seems like this is not likely, as in, if would have been caught already. it seems far more likely for everyone to have missed the base assumptions that just don't make anyone any money.

 

I noticed some rust on both front hubs when I did the brake job a year ago. I used a wire brush on the hubs and placed a small amount of Permatex purple brake lube (I forget where I learned to do this and weather its a good idea or not), cleaned the 15ml ECS spacers and mounted the wheels. I don't remember looking at the inside mounting surfaces of the wheels. I'll redo all this when I tear it all apart soon.

The car does not "pull" when braking at any speed. The Zimmerman rotors are not warped.

The rear passenger side bearing is the only one that has been replaced since the car was new.

If I perform the low speed "right to left and left to right test;" what should I be observing? Noise? I'll check for grinding when I get the car in the air. I'm starting to suspect the wheel bearings.

I don't know what a "runout measuring tool" is; or how to use it. I'll head to Google after this post.

One last thought and question. Can reuse of Caliper Bolts be an issue? I torque them down to spec each time I've reinstalled them. I had them off a few months ago to gain access to the front drive (diff) for an oil change.

Thanks for ALL the feedback!

 

Not sure if your vibration issue but caliper bolts are one use.

 

You should be looking for some kind of noise when doing the wheel bearing road test. Generally braking related issues aren't related to wheel bearing failure but in your case there isn't much left to replace so its worth a look. I would corner hard left to right and also apply brakes during the test to see what happens. Maybe have someone ride along and listen with you. The other thing that hasn't been mentioned is to check the cv axle and where it mounts up to the differential flanges. Those have rubber in them that could be failing or the bolts are coming loose. Give the axles a good shake while the front is in the air and look for any kind of play in that area. The passenger side is the differential side and the drivers side has a carrier with a bearing that does fail from time to time which could cause noise or vibration.