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How to measure toe yourself (with pictures)

Discussion in 'Model S: Driving Dynamics' started by zwede, Jul 5, 2014.

  1. zwede

    zwede 2013 P85+

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    #1 zwede, Jul 5, 2014
    Last edited: Jul 11, 2014
    The question of rear toe comes up on a regular basis and how one might measure it. As many of us have found out, having incorrect rear toe will quickly destroy tires. This is especially true with the 21" wheels as their shorter sidewall is less able to compensate for incorrect alignment.

    First a quick recap of what toe is:

    WhatIsToe_zpsf7fdc67a.jpeg

    What we want in the rear is a slight toe-in. This is so that when the torque of the motor propels the car forward, suspension bushings deflect and the wheels point straight.

    The current spec for the Model S is as follows.


    MinMax
    Total rear toe-in (degrees)0.250.45

    Note:
    This spec differs slightly from the one in the owner's manual. I received this in response to an email I sent to Tesla ownership 07/11/14 asking for the latest spec.

    Measuring this on your own is fairly simple. All that is needed are 2x jack stands, some string, and calipers.

    Place one jack in front of the car and one behind and run the string between them. Place the stands so the string is 45 mm from the rear center cap and 64 mm from the front.

    Here I'm setting the rear distance to 45 mm.

    Toe_1_zpseaef5628.jpg

    Placing the string like this makes it run exactly parallel to the car. The 45 mm / 64 mm setting works on all factory wheels. 19" as well as 21", including the staggered P85+.

    Next I measure the distance from the rear rim lip to the string. Note that I'm measuring from the rim, not the tire.

    Toe_2_zps5356896e.jpg

    I ended up with a measurement of 9.2 mm.

    Finally I measure the front lip to the string.

    Toe_3_zpsea5d9083.jpg

    And this was 10.2 mm.

    So what do my measurements mean?

    My front distance is greater than the rear. I have toe-in.

    The difference is 1 mm. Turns out each mm of difference corresponds to ~0.1 degrees with 21" wheels, and ~0.11 degrees with 19". You can do the trig, or just use my numbers. :)

    So on the right rear wheel I have 0.10 degrees toe-in. On the left I have 2 mm, or 0.20 degrees.

    My total rear toe is thus 0.30 degrees toe-in. With the spec being 0.25-0.45, my rear toe is in spec.

    Don't worry about small differences side-to-side. They are not harmful. If the difference is too large the car will go down the road sideways, but 0.1 degree is nothing to worry about.

    So that's how easy it is to check your toe. You can measure the front wheels the same way. Make sure the wheels are pointed straight. In the front the spec is:

    Air suspension: 0.10 toe-in to 0.30 degrees toe-out.
    Coil suspension: 0.24 toe-n to 0.16 degrees toe-out.

    Yes, it is OK to have slight toe-out in the front. The drag of the wheels deflects the suspension bushings differently than in the rear, so a slight static toe-out is not a problem.
     
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  2. drees

    drees Active Member

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    For measuring other cars, what's the easiest way to make sure the strings are parallel to the car?

    For the Model S, 45 mm / 64 mm I assume is relative - you just need to make sure that the rear is 19 mm greater than the front...
     
  3. zwede

    zwede 2013 P85+

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    If you know the track width of the car and the rims are the same rear and front you can use the difference between front/rear track. If the rims are different you may end up running string on both sides and then measure the distance between the strings until you get them equal. Of course you also need to make sure the car is right in between the strings.

    Correct.
     
  4. tezco

    tezco Sig P85

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    Thanks for the tutorial. I'm have to give it a try.
     
  5. redi

    redi 2013 P85+ http://ts.la/dale2363

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    While you can only get a total toe measurement, toe plates seem to work and you can read the tapes down to about 1/64". Takes about 3 minutes to get a check. There are cheaper and more expensive models, the more expensive have arms to touch only the wheel rim. The plus part is that it does literally take about 3 minutes to check.

    Deluxe Toe-In Plates (pair)
     
  6. Lasttoy

    Lasttoy Member

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    Mine tracks fine. BUT, just ruined rear inside tread. Metal cords were showing, tread on outside. I have to fix it. I just installed new tires. Front tread was equal on both sides.
     
  7. Lasttoy

    Lasttoy Member

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    I forgot, does anyone know how to adjust it ? I just went alignment shop, he wouldn't touch it.
     
  8. zwede

    zwede 2013 P85+

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    I think it can be adjusted without removing the wheel if it's on a lift, but since I only have jack stands I have to remove the wheel to adjust. With the wheel removed you'll see the toe link with one end attached to the wheel hub/knuckle and the other end to the frame. The inner mounting point has an eccentric. Note there are two links. The rear one is for camber (non-adjustable). The front one is toe.

    Make a mark with a felt tip pen on the eccentric, then loosen the nut and turn the bolt. Very small adjustments make a big difference in toe. It is very tedious getting it right as you have to re-install the wheel and drive around the block before you can measure again.
     
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  9. Naonak

    Naonak Member

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    I have a lift... how would I adjust it myself? Same deal? Do I have to drive it around to recheck it, or can i use some plates (previously linked) and just adjust the bolt until it lines up with what I want?
     
  10. zwede

    zwede 2013 P85+

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    I would say you still need to drive it before doing the final check. But being able to adjust it with wheels on will save you some time.
     
  11. aesculus

    aesculus Still Trying to Figure this All Out

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    The crab effect. :D

    Great write-up.
     
  12. Buook

    Buook Member

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    Thank you this is helpful
     
  13. timvracer

    timvracer Member

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    I used to use 2 round sheet metal plates (about 2' diameter) and put grease between them (skid plates). I had them for all 4 corners, then I could just drop the car on the plates, bounce it up and down, and settle the suspension - then remeasure the toe.

    Even if you drive around, how you pull in and park can mess up things if you have anything "bound up".
     

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