Measuring the Tire Tread Depth on an Aston Martin DB9

Measuring the Tire Tread Depth with a Vernier CaliperMeasuring the tire tread depths on your DB9 is part of every annual service.  This isn’t a sexy topic, but it is a very useful one if done correctly.  By measuring and reviewing the data properly, you can actually spot issues with your suspension, tire pressures and wheel balance.

I’ve used the official Aston Martin Vehicle Inspection Checklist as my guide on what we should be checking.  You can see a copy of it here.  You’ll notice this isn’t just ‘take a quick peak at the wear markers and call it good’.  Read on to learn how.

You might be interested in my other tire related posts and videos:

Measuring Tire Tread Depth and Reviewing for Uneven Wear

So this is a tedious step, but is very useful as it will discover if your tires are wearing unevenly, or need replaced.

DB9 SuspensionA worn suspension, incorrect alignment, poor wheel balance, and improper tire pressures are just some of conditions that can wear a tire unevenly.  I don’t plan on covering those conditions here, but want you to be able to collect the data and know when you have an irregularly worn tire so that you can be alerted to take your car in for professional help from the Dealer.

4 Clock PositionsThe official Aston Martin Vehicle Inspection Checklist wants us to check the remaining tread depth in the four grooves on the tread face, at four positions around the tire.  That’s 4 readings at 4 positions, 16 total per tire.  Four tires later and that’s 64 data points.   Tedious yes, but really only takes about 10 minutes total.  Check out the video below to see the procedure I followed.

The Vehicle Inspection Checklist has a table for the data.

I used a digital vernier caliper to make quick work of the measurements, but there are other tread depth measuring devices that can work.  You don’t need to be precise to the thousandth of an inch, but you don’t want to use a tape measure or ruler either.  The wear patterns can be subtle to detect.

When the Bridgestone OEM tires are new, they have 11/32 (0.34″) of tread depth.

Tread Wear Indicator Strip
Tread Wear Indicator Strip

All tires have a wear indicator built into the grooves to make it easy for you to spot when your tires need replaced at 3/32″ (0.10″) of tread depth.  If the treads and wear strip are one continuous surface, you are at or below 3/32″ and need to replace the tires.

The ideal situation would be to have the same tread depth remaining in all four grooves at all four positions around the tire, a sign that it’s worn completely evenly.  If this happens to you, it’s a miracle.

What’s more realistic is to have _almost_ the same readings at most locations.  Look at your data for these common signs of a problem:

  • If the tread depth is less than 0.10″ at any position the tire is worn out and should be replaced (in sets)
  • Both outside grooves more worn than the inside
    • Possibly a sign of under inflation
    • Possibly a sign of aggressive driving (track day)
  • Either just the inside or outside groove worn more than other three
    • Possible suspension misalignment
  • Both center grooves more worn than the two outside
    • Possible sign of over inflation
  • Depth of groove is varying as you move around the rim
    • Possible sign of tire imbalance
    • Possible sign of worn suspension
  • Sloping tire depth from inside to outside or vice-versa
    • Possible sign of suspension issue

If you have one of these anomalies you might want to consider having your dealer check out the car.  Personally I wouldn’t let a local tire shop fiddle with my suspension.  Change a tire on a rim – yes.  Diagnose and adjust alignment – no.  [A private shop that specializes in Astons is fine, but not a generic tire shop]

I am developing my own version of the Check List table in a simple spreadsheet that will look at the data for us and note the anomalies in a easy to understand visual format.  Stay tuned for this….

Here is a quick video describing how to collect the information.

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