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Negative Camber in the Rear and Expensive Tires
- Thread starter lolachampcar
- Start date
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- Driving Dynamics Model S
They did the alignment in late December. I asked them to check it for precisely this reason. Now I'm wondering if they had the right update on the machine at the time.
Even without the right update, I do not think there is a good alignment tech on the planet that would put toe out on MS on purpose and the machines display/print absolute information in addition to data conformance to specification.
I've got a P85 with 19s and I'm at 46k miles now still driving on the original tires. so no, don't hold off. Buy the car. Like yesterday. lol you won't regret it. yes I do check my tires and tire pressure every other week. rotated at 6k, 24k, 36k, and 46k. probably going to get new tires within the next week or two as I am down to about 4/32" with slight inside edge wear. I just had my car serviced last week so that included new camber bolts and an alignment. I should be good to go for another 50k miles on my new set
I've got a P85 with 19s and I'm at 46k miles now still driving on the original tires. so no, don't hold off. Buy the car. Like yesterday. lol you won't regret it. yes I do check my tires and tire pressure every other week. rotated at 6k, 24k, 36k, and 46k. probably going to get new tires within the next week or two as I am down to about 4/32" with slight inside edge wear. I just had my car serviced last week so that included new camber bolts and an alignment. I should be good to go for another 50k miles on my new set
Can you post your alignment spec sheet? That is some impressive tire longevity for a P85. My 19" Goodyears are close to shot with only 17k miles on an S85. Its mostly inner tire wear, and the car is aligned to Tesla spec. My rear camber was only -1.36.
Spec allows for a good bit of toe in. Ask for the near zero side of the spec for improved wear.
That's what I don't understand, rear toe was set to 0.02" for a total of 0.04 on the rear. It shouldn't be wearing the way it is. I've got some bolts coming from Tesla and will try to get camber closer to -1.10 on the rear, and see how that works with the new tires.
You can check toe yourself. You need 2 jack stands, string, and digital calipers. The Chinese calipers you can get for $10-$15 work fine.
Tie the string between the jack stands and place along the side of the car. The string should run at the height of the rim center caps. Use the calipers to set the distance from the center cap to the string to 45 mm at the rear and 64 mm front. Next measure the distance from the string to the edge of the rear rim (front and back). If the rear edge of the rim is closer to the string than the front you have toe-in. Each millimeter of difference translates to right at 0.1 dgr. Total toe is both sides combined and should be 0.1 to 0.3 dgr (1-3 mm). Example:
Left rear wheel has 10 mm at the back, 9 mm front -> 0.1 toe-out (or -0.1 toe-in)
Right rear wheel has 8 mm at the back, 11 mm front -> 0.3 toe-in
Total rear toe: 0.3 + (-0.1) = 0.2 toe-in.
Tie the string between the jack stands and place along the side of the car. The string should run at the height of the rim center caps. Use the calipers to set the distance from the center cap to the string to 45 mm at the rear and 64 mm front. Next measure the distance from the string to the edge of the rear rim (front and back). If the rear edge of the rim is closer to the string than the front you have toe-in. Each millimeter of difference translates to right at 0.1 dgr. Total toe is both sides combined and should be 0.1 to 0.3 dgr (1-3 mm). Example:
Left rear wheel has 10 mm at the back, 9 mm front -> 0.1 toe-out (or -0.1 toe-in)
Right rear wheel has 8 mm at the back, 11 mm front -> 0.3 toe-in
Total rear toe: 0.3 + (-0.1) = 0.2 toe-in.
also, 0.4 degrees of toe in is towards the maximum toe in allowed by specification (if memory serves me correctly - please feel free to correct me). I put mine at 0.1 total toe in on the rear which may actually be a little under what Tesla wants. My car hunts on the highway a bit more with this setting but rolling resistance is down, range comes up and my tires are wearing more evenly. If I remember correctly, I have about 1.2 degrees of negative camber on all four wheels.
This is how I got a quick repeatable toe set up for my car when I was developing the upper links.
Tesla Alignment
This is how I got a quick repeatable toe set up for my car when I was developing the upper links.
Tesla Alignment
So... I've been wondering about the fact that the car was extremely loose in the rear under heavy acceleration. Thought maybe it didn't have the new bushings or camber bolts, but that wasn't the case.
Then the car just burned through a set of the PS2s in less than 6k miles. Inside edge completely corded, while the middle wasn't even on wear bars. I knew it was abnormal wear, I had these exact same tires on my Porsche several times, and managed very consistent wear across the back and mileages around 10k -- despite driving the Porsche much harder.
Did some investigation and found an independent shop to align my car. What I found was -0.25 toe (out) on the rear tires. On each side. In December, it was aligned by the service center to -0.25 and -0.19. The alignment machine printout I have says that the specified range is -0.30 to -0.10, but I'm seeing actual factory specs somewhere in the neighborhood of +0.20 (toe in). Can't imagine why that would cause the inner tire to wear out dramatically faster than the rest of the tire.
So, if you're having extreme wear on the inside edge of the rear, verify your alignment settings and make sure you have toe IN, not toe OUT on the rear.
Then the car just burned through a set of the PS2s in less than 6k miles. Inside edge completely corded, while the middle wasn't even on wear bars. I knew it was abnormal wear, I had these exact same tires on my Porsche several times, and managed very consistent wear across the back and mileages around 10k -- despite driving the Porsche much harder.
Did some investigation and found an independent shop to align my car. What I found was -0.25 toe (out) on the rear tires. On each side. In December, it was aligned by the service center to -0.25 and -0.19. The alignment machine printout I have says that the specified range is -0.30 to -0.10, but I'm seeing actual factory specs somewhere in the neighborhood of +0.20 (toe in). Can't imagine why that would cause the inner tire to wear out dramatically faster than the rest of the tire.
So, if you're having extreme wear on the inside edge of the rear, verify your alignment settings and make sure you have toe IN, not toe OUT on the rear.
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In the case of my service center, the specs programmed into the machine were wrong and the service center had to get Hunter (machine manufacturer) out to program the proper numbers into the machine. You have likely been hit by that as well.
The reason you end up with inner shoulder wear is that the negative camber plus the toe-out ends up creating an intersection point on the inside shoulder where tire meets the road.
After extended conversations with the service center, that does indeed appear to be the case.
Keep in mind, their service techs kind of do everything. They don't have an "alignment guy" and even if they did, the only cars they ever see are made by Tesla. Since they don't know alignment and don't have a lot to compare it to, they have to trust that the numbers in the machine are correct. For someone like me, who races and instructs race drivers, the alignment is obviously wrong just from a visual spot check, but you have to know what you're looking at. I cannot stress enough that the techs nor their training is at fault here. They only have to know how to align a car, they don't have to understand why the alignment works (or doesn't). Most of the technology we use every day is like this -- we know we bake a cake at 325 degrees for 40 minutes because that's what the box says, but do we know why? If a cake mix said bake at 400 degrees for 20 minutes and it was the second cake we'd baked, would we know enough to say it's wrong?
For everyone else, tire wear like this isn't normal. There is no reason a car should wear the inside edges of the tires that much sooner than the outside. If it is, then the car is set up wrong and needs to be realigned. That's not to say you might hit the cords on the inside and still have tread on the outside, but it should be a gradual fade and the overall difference negligible. Yes, performance tires do not last and you should not expect to get more than 10k out of the PS2s, but you should experience even tread wear across the tire.
The service center verified that the specs in the alignment machine did not match the factory alignment specs when my car was aligned. Additionally, they've reached out to other Austin area owners who have had their cars misaligned as well. They agreed to compensate me for the increased tire wear and I'd say that makes this outcome a positive one, even if the road there was a little rocky.
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Wheel Alignment Explained
Larger amounts of toe (positive or negative) plus larger amounts of negative camber will tear up the inside shoulder of the rear tire. Toe out is worse than toe in but both are bad.
If you choose to stay with Tesa's camber geometry, you will be best served for tire wear by using as little toe in as possible. The possible will either be the minimum of the Tesla specification or a lesser number of your choosing if you are comfortable dictating toe values.
Larger amounts of toe (positive or negative) plus larger amounts of negative camber will tear up the inside shoulder of the rear tire. Toe out is worse than toe in but both are bad.
If you choose to stay with Tesa's camber geometry, you will be best served for tire wear by using as little toe in as possible. The possible will either be the minimum of the Tesla specification or a lesser number of your choosing if you are comfortable dictating toe values.
mnx
2018 M3P
I think once I replace my tires I'm going to get the car re-aligned for as close 0 toe as possible. When I had an alignment done in January it was set to @ 0.21 deg toe in on each side in the rear.
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