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Old 01-18-2019, 08:29 AM
Knoxes Knoxes is offline
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Mein Auto: Starts on the second pull
Highway speeds instability

I just had new tires (Michelin PS AS3+) installed and an alignment done yesterday. Here are the results:

I had a chance this morning to test drive and it felt mostly ok up to 70mph. Above 60mph, it starts to feel very light in the front. At 70, it feels really windy out, even though its not. I pushed it briefly up to just over 100 and it really floats at that speed - very unsettled. Is the rear out of spec causing that float?
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File Type: pdf e86 Alignment 1-15-19.pdf (298.1 KB, 41 views)

Last edited by Knoxes; 01-18-2019 at 08:37 AM.
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  #2  
Old 01-18-2019, 08:48 AM
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Doug Huffman Doug Huffman is online now
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Or the front out of spec? Why did you specify / allow those numbers for your alignment? Read and understand your alignment allowable specifications AND THEIR EFFECTS. Tell the mechanic the allowable numbers that YOU want. This one mechanic was in a hurry to get to his hydraulic lunch.
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Old 01-18-2019, 09:19 AM
Knoxes Knoxes is offline
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Mein Auto: Starts on the second pull
Yup. My mistake. I've had them do alignments before and it's handled fine. So I assumed they knew what they were doing and I didn't pay much attention to the actual measures as long as they were in spec.

I've noticed your activity along with Ard's in a couple of threads on alignment issues - thanks for your contributions on the topic. This morning I sent an email to the store manager requesting all toe to 0.02 based on ard's specs, so we'll have another go at it.
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Old 01-18-2019, 10:05 AM
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Check your front & rear suspension bushings too. You'd be amazed at how much bad rear bushings impact handling.
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Old 01-18-2019, 06:10 PM
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The near zero rear toe certainly isn't helping things. A bit of rear toe gives stability. If you go to zero toe front and rear you maximize rotation which is the opposite of being stable at speed.
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Old 01-21-2019, 08:47 AM
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Also, I would allow for at least 200-300 miles before testing the tires. Tire mold release agents can cause the tires to behave differently at first.

Steve
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Old 01-21-2019, 09:06 AM
Z4530i Z4530i is offline
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Need some cycles on the tires, at least 300 miles.
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Old 01-22-2019, 08:38 AM
Knoxes Knoxes is offline
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Mein Auto: Starts on the second pull
I went back and had them adjust all 4 corners to 0.02. Interestingly, less than a week had passed since the first effort and they somehow came up with different "Before Measurements", which didn't match the "Current Measurements" from the previous visit. I guess I would expect some minor variance, but I'm not sure how you get to from -0.01 total rear toe to 0.27 in less than a week.

Also, in reviewing the specs, was the rear supposed to 0.04 total? According to the image, that's toe out.

I've put a few miles on it since yesterday and it's much better at highway speeds, but still a little darty.
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Last edited by Knoxes; 01-22-2019 at 08:42 AM.
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Old 01-24-2019, 03:37 PM
keeton keeton is offline
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Quote:
Originally Posted by BostonB6 View Post
Check your front & rear suspension bushings too. You'd be amazed at how much bad rear bushings impact handling.
This bears repeating. The front arm control bushings (FACB) are a known wear point for the Z4. It starts showing up at around the 60,000 mile mark and can cause exactly the symptoms (loose steering, floaty feeling) you are describing.

If the bushings are worn, you will NEVER be able to align the vehicle properly because the suspension bits will be constantly shifting around.
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