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:
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.
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.
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.
I ended up with a measurement of 9.2 mm.
Finally I measure the front lip to the string.
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.
First a quick recap of what toe is:
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.
| Min | Max | |
| Total rear toe-in (degrees) | 0.25 | 0.45 |
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.
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.
I ended up with a measurement of 9.2 mm.
Finally I measure the front lip to the string.
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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