On Fri, 18 Dec 2020 16:20:42 -0600, Paul in Houston TX wrote:

> IMO, mileage estimates seem to be for straight line, 50 mph, constant
> temp and load.

While the manufacturer stamps the tires with the treadwear indicator, they
do so following an exacting driving procedure handed to them (AFAIK) by the
DOT and/or the NHTSA to be run always on a specific San Angelo TX test
course always with a specific driving pattern for all tires being tested.

Let me dig that test track information up...
o <https://one.nhtsa.gov/DOT/NHTSA/Vehicle%20Safety/Test%20Procedures/Associated%20Files/TP-UTQG-W-01.pdf>

That document is labeled "TP-UTQG-W-01" US DOT NHTSA
o "Procedures for tire treadwear testing"

Skimming that document there is a Test Program Overview at section 1-12.
"The tires will then be labeled, inspected, mounted onto rims,
balanced and then placed onto the test vehicle. The test vehicle will be
ballasted to achieve the required loading of the tires. The vehicles
will be driven over the established 400 mile course utilizing the
prescribed driving technique for a total of 7,200 miles. After each 800
miles, the tire pressure and tire depth will be measured, the tire
position will be rotated, and the vehicle's front end alignment will be
adjusted when required. At the completion of the test the wear rates of
each tire will be calculated."

And here is a course overview at section 5-12:
"The course consists of 3 loops as follows:
1. Southern Loop
2. Eastern Loop
3. Northwestern Loop

I had originally thought it was a test 'track' but skimming the document
shows it's actually real roads and intersections such as STOP at FM388 for
the Calibrated Mile and U-Turn at the Camp Hudson Historical Marker, and
then drive on US277 for 88 miles, then drive on Sonora Road for 214 miles,
and stop at FM388 & FM2334, etc.

There's a map of the three loops which looks like a bow tie around a
Christmas present, where the southern end is just a bendy ribbon while the
two northern ends are both clearly large loops.

Anyway, my quick summary from a quick skim is that it's on "regular" roads
in Texas, where it's regular driving (they even tell the driver what the
braking & yield procedures are in the document).

When they check treadwear, they check it at 6 marked locations, starting at
the DOT number avoiding treadwear indicator bars.

It's not all straight but it's not all curves either.
o It sure does seem like it's seven thousand miles of "normal driving",
albeit I live on a mountain so none of that is covered in this test.

See also:
o Does the macadem road surface have a great effect on tire wear?
<https://groups.google.com/g/alt.home.repair/c/ZwIeZHNCzpI>
o Questions about mounting & balancing new LT tires on new steel rims at home (match mounting marks, red dots, yellow dots, & spacers)
<https://groups.google.com/g/alt.home.repair/c/gjsqxRxTacw>
o Clare, Xeno.... did you ever have a batch of tires that just wouldn't seal after the final bead?
<https://groups.google.com/g/alt.home.repair/c/ST-xNgC5pnU>
o Just mounted & static balanced my 30th tire in about five years - saving over $400
<https://groups.google.com/g/alt.home.repair/c/zfyOpil5bck>
o Can you return a tire you don't like for full refund?
<https://groups.google.com/g/alt.home.repair/c/5htRVubIoW8>
o What metric do you use to estimate remaining brake pad life on a typical economy sedan?
<https://groups.google.com/g/alt.home.repair/c/C2VH6EvL2As>
--
Posted, as always, out of the goodness of my heart, in order to help.