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My perfect alignment quest (long but with new info and happy ending)

Discussion in 'Model S: Driving Dynamics' started by zwede, Apr 17, 2014.

  1. zwede

    zwede 2013 P85+

    Joined:
    Jan 17, 2014
    Messages:
    501
    Location:
    Plano, TX
    First I want to say this post is not a slam on Tesla. They are trying very hard to be the best. I have worked on cars as a hobby for 25 years and long ago realized it is impossible to get a perfect alignment at any shop. I believe this is because the alignment machines quickly go out of calibration and there's no easy way for the tech to know it's out.

    So after that little intro, some quick background. I bought my inventory P85+ in January with 5,800 miles on it. It had had 19" wheels on it for 2,000 of those miles. With 3,800 miles on them, the rear 21" tires (Michelin PS2) had quite a bit of wear, and it was also uneven. Outer groove was 7.5 mm, inner 5 mm. Meaning the tires were more than 1/2 worn in only 3,800 miles. Part of that wear was of course from being an inventory car (test drives), but that didn't explain the unevenness.

    I took it to the Dallas SC and they installed the camber bolts and aligned it. I got the following specs from them.


    FrontRear
    Camber-0.8/-1.0-1.3/-1.6
    Toe0.15 (IN)0.15 (IN)




    After that the rear tire wear evened out a bit, but they were still wearing fast. 1,000 miles later the inner groove was 4,5 mm and the outer 6 mm. I decided to measure the alignment myself:



    FrontRear
    Camber-1.1/0.0-1.7/-2.0
    ToeN/A0.80 (OUT)




    I didn't measure front toe as I realized I needed to tweak RF camber anyway. Notice the 0.80 dgr toe out in the rear!

    To fix the rear camber I adjusted the air suspension travel sensors. By elongating the mounting holes I was able to rotate them slightly which raised the rear 12 mm. Due to the camber gain curve, this decreased camber 1/2 dgr. My final alignment numbers are:


    FrontRear
    Camber-0.9/-0.7-1.3/-1.5
    Toe0.00.10 (IN)




    The first thing that struck me when driving it is how smooth it feels. It is like when you drive on concrete and then there's a section with asphalt. Suddenly it's like driving on glass. That's how it feels now.

    The next thing I noticed was my average energy usage ticking down. Previously my commute averaged 370 wh/mile. My 30 mile average after driving to work was 342, and my commute is only 7.5 miles. My last 5 miles averaged 269 wh/mile (I've never seen <300 before).

    So in closing I'll again say I'm not slamming Tesla. Alignments are a difficult area for all shops. Tesla isn't immune to the issues that plague professional alignment machines. Another problem with alignments is that you really need to drive the car after each change. I've spent 10 hours over 5 days doing this. It's not reasonable to expect a shop to invest that kind of time, and no customer would be willing to pay for it.
     
  2. yobigd20

    yobigd20 Well-Known Member

    Joined:
    Oct 28, 2012
    Messages:
    5,793
    Location:
    Skaneateles, NY
    how does one measure their own alignment without an expensive machine?
     
  3. zwede

    zwede 2013 P85+

    Joined:
    Jan 17, 2014
    Messages:
    501
    Location:
    Plano, TX
    Slowly, unfortunately.

    Camber is easy. I have a Longacre camber gauge:

    F14606152.jpg

    Toe takes me forever. There are some toe gauges I've been looking at, but currently I'm doing it the hard way:

    I have a level which I tape 2 sockets to so they contact the edge of the rim and not the tire. At the end of the level I hang a weight off a string which has a pointed end. A put masking tape on the floor and make a line where the weight contact it. I do 8 of these, front and rear of each wheel. I can then measure the distance between the lines in front and behind the wheels. Take the difference, divide by the front-rear distance and do Atan on the result and I get the angle. Of course after each adjustment I get to do all 8 tape pieces and measurements again. Takes quite a bit of patience. :) A toe gauge like this is probably my next purchase:

    796201365008946515c6232063ff.jpg
     
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