Symptoms of unbalanced or warped rotor? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

speedyspaghetti · 09-20-2018, 07:58 AM

Hey guys -

This weird vibration I'm feeling through my steering wheel is driving me insane. I have replaced literally everything in the front suspension, including my wheel bearings. Each thing I have done has made it a bit better, but it is still present, especially at highway speeds. I'm pretty certain it is coming from my front left wheel because the side-view mirror vibrates rapidly when I'm driving.

Is it possible that an unbalanced or warped rotor could be causing this? My rotors have a pretty significant lip on them, but I don't hear any serious scraping when I lift the car and spin the wheels, just the brake pad lightly touching the rotor.

Any ideas would be greatly appreciated - I'm getting to the point where I'm thinking of selling the car since I've been trying to track this thing down since last October.

In case someone asks, here is what has been replaced:
Tie rods (in & out)
Drop links (front)
Struts & Strut mounts (front and rear)
Control arms (front and rear)
Front tracking arms
Rear trailing arms
Wheel bearings (front)
Tires (Continental ExtremeContact DW)
Sway bar bushings (front and rear)
Multiple alignments
Multiple tire balances

All parts are OEM.

Topless · 09-20-2018, 08:18 AM

If it happens all the time at speed it is a most likely bad tire or bent wheel. The wheel balance guys should catch that.

If it only happens under braking, it is rotor judder from uneven pad transfer. With a significant lip on your rotors I would measure them for runout and probably change them. I don't like worn rotors and they are not very expensive.

PaulE · 09-20-2018, 08:27 AM

When I was going through the same issue my shop said brake rotors were not the issue. If your rotors were warped (which is actually an uneven level of brake pad material built up around the disk surface), you would feel it in the brake pedal pulsing when you brake at moderate to hard levels. I don't know about disks being out of balance. Do you have any friends with a Boxster who don't have vibration issues? If you do and they are willing to help out, you can swap wheels and tires and see if the vibration appears on your friend's car and disappears on your car. That would tell you the problem is in your wheels and tires. If you don't have a friend who can volunteer to help like this, maybe you Porsche shop can do it with another set of wheels and tires. The only other thing that comes to mind is the condition of your motor mount. If you are driving at the speeds when you feel the shimmy in the wheel, and take your hands off the wheel, do you still feel the shimmy through the seat of your pants? In that case it could be your motor mount starting to go.

From my own experience with just a 2003 Boxster S that I've owned since new, I think these cars are extremely sensitive to tire brand, road surface, tire pressure, and fuel tank level. When I bought my 17 inch wheels I bought a new set of Toyo Proxes T1 Sport tires. One of the fronts was so bad I had it replaced under warranty. Even then they were so bad that I threw them away after less than 8,000 miles and bought Michelins which were much better, and I would have saved a lot of money from having my shop going over my car if I just bought the Michelins to start with. Once you get this resolved though, I think you will still always feel a little something in the steering wheel due to the nature of the car.

I hope you can get to the bottom of this!

MWS · 09-20-2018, 08:34 AM

It seems like you have done more than your due diligence; I can, however, share a (maybe) relevant story. Years back (and a different car) I had a vibration that I attributed to a tire, and as they needed replaced anyway, I had new ones put on at a tire shop. New tires, but same vibration....I attributed this to incorrect balancing, so I went to a different shop to check the balance, which turned out to be good. I really wanted this vibration addressed, so I asked what else they could look at and they suggested the rim. As I wasn't in the shop at the time, all I know is that they found a defect and corrected (assumed by grinding down) remounted tire and balanced. Magically the vibration went away. Again, I don't know exactly what the issue was or how it was corrected.

Sorry I can't answer your question about the rotor. ;(

+1 on the idea of swapping out wheels.

speedyspaghetti · 09-23-2018, 10:01 AM

Quote:

Originally Posted by Topless

If it happens all the time at speed it is a most likely bad tire or bent wheel. The wheel balance guys should catch that.

If it only happens under braking, it is rotor judder from uneven pad transfer. With a significant lip on your rotors I would measure them for runout and probably change them. I don't like worn rotors and they are not very expensive.

So I went to a reputable wheel repair shop and they check all four wheels and also put them on the Hunter Road Force machine in front of me and no imbalance and bend could be detected. They were incredibly nice and didn't charge me a penny (I bought them lunch instead) but I'm still at a loss for what could be causing this.

The steering kind of self-steers when I'm on a bumpy road - it pulls left and right a lot more than it should. Could the steering rack be potentially bad?

speedyspaghetti · 09-23-2018, 10:03 AM

Quote:

Originally Posted by PaulE

When I was going through the same issue my shop said brake rotors were not the issue. If your rotors were warped (which is actually an uneven level of brake pad material built up around the disk surface), you would feel it in the brake pedal pulsing when you brake at moderate to hard levels. I don't know about disks being out of balance. Do you have any friends with a Boxster who don't have vibration issues? If you do and they are willing to help out, you can swap wheels and tires and see if the vibration appears on your friend's car and disappears on your car. That would tell you the problem is in your wheels and tires. If you don't have a friend who can volunteer to help like this, maybe you Porsche shop can do it with another set of wheels and tires. The only other thing that comes to mind is the condition of your motor mount. If you are driving at the speeds when you feel the shimmy in the wheel, and take your hands off the wheel, do you still feel the shimmy through the seat of your pants? In that case it could be your motor mount starting to go.

From my own experience with just a 2003 Boxster S that I've owned since new, I think these cars are extremely sensitive to tire brand, road surface, tire pressure, and fuel tank level. When I bought my 17 inch wheels I bought a new set of Toyo Proxes T1 Sport tires. One of the fronts was so bad I had it replaced under warranty. Even then they were so bad that I threw them away after less than 8,000 miles and bought Michelins which were much better, and I would have saved a lot of money from having my shop going over my car if I just bought the Michelins to start with. Once you get this resolved though, I think you will still always feel a little something in the steering wheel due to the nature of the car.

I hope you can get to the bottom of this!

Thanks for the input! Had the wheels and tires looked at yesterday and the techs said that they looked perfect. It does not really make sense for it to be a brake rotor thing, but I'm running out of things to chance. Good idea on the mount - I have the insert to replace, I just need to find a shop to push out the old one and put in the new one. Also, I need to find some time to get under the car and change it out.

I've had this problem on both my old tires (which were fine for a long time) and my new tires, so I don't think it is the tires.

The Radium King · 09-23-2018, 10:07 AM

i get vibration at speed. what research i've done indicates that the issue is with worn bushings in the front lower control arms. you can get your mechanic to go at it with a crowbar to see if there is any play, but typically the wear is only really apparent upon removal of the lca and visual inspection.

speedyspaghetti · 09-23-2018, 10:45 AM

Quote:

Originally Posted by The Radium King

i get vibration at speed. what research i've done indicates that the issue is with worn bushings in the front lower control arms. you can get your mechanic to go at it with a crowbar to see if there is any play, but typically the wear is only really apparent upon removal of the lca and visual inspection.

I've replaced all four control arms with Meyle OEM parts - anything else that could be contributing to this?

The Radium King · 09-23-2018, 01:00 PM

damn, i read your list or work done twice and somehow missed that.

any play in steering rack?

speedyspaghetti · 09-23-2018, 06:04 PM

Quote:

Originally Posted by The Radium King

damn, i read your list or work done twice and somehow missed that.

any play in steering rack?

I'm not 100% sure how to check for that. If I lift both front wheels off the ground and grab them at 9 and 3, it will rock the steering wheel back and forth, but I'm guessing that's normal?