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2011 ML350 4Matic
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Discussion Starter #1
In my 2012 S65 I hit a big pothole and blew out my left front sidewall (sounded like an explosion from inside the car). I replaced the tire, and a couple thousand miles later I noticed significant wear on the inside edges of both front tires. I took it in to the dealer for an alignment and the right tire was so badly worn it had to be replaced too. My front total toe was way off - it was almost one degree toed out and it is supposed to be toed in by a small fraction of a degree (16 minutes of arc).

Recently I hit another pot hole that was not nearly as bad, but still a pretty violent event and I fond myself wondering if I needed another alignment. I read up on how to use strings to pretty accurately check the alignment and I did this check in my garage. People who autocross and take their cars to the track seem to use this type of system regularly to avoid the need to take their cars in to the alignment shop, and they seem to feel better about the results they get from this type of system. Using this string system I found out that my toe setting was still within the specifications.

You can do this check by setting up two strings parallel to the centerline of the car, one on each side going past the wheels at axle height. Then the toe-in or toe-out can be measured using this string as a reference. I used a long level connected to my wheel to magnify the difference in distance to the string from the front of the wheel compared to the back of the wheel to improve accuracy.

I made this youtube video to explain how to do this.
String alignment check

Camber can also be checked at home but that requires some tools and my pothole experience showed that the main thing affected on my car was the toe and not so much the camber. To check camber you need an inclinometer that is pretty accurate. I tried using an app on my phone, but I don't think that is really accurate enough.

The low profile tires used on our high-performance cars are really not compatible with potholes. Most cars with bigger sidewalls go right over these potholes and their occupants feel the bump, but there is no damage because the sidewall can absorb the shock. If you find yourself in this same dilemma after hitting a major pothole then you have this as an option to check before going through the hassle of taking it to the shop. It is a bit of a hassle to set it up the first time, but once you have all of the stuff, it is much quicker to set it up the second time. If you want the Excel spreadsheet I that I used, I can send it to you. I hope this was helpful.
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