The extended tread-life test on CR's Sienna AWD continues.
For those who have been following our saga of run-flat tires on our 2007 Toyota Sienna XLE AWD, we've been raking up the miles faster than you can say "minivans are the best family vehicle EVER!" After hearing many tales of premature wear of the original-equipment Dunlop SP Sport 4000 Self-Supporting Technology tires (DSST)—run-flat tires, in layman terms—we decided to do a long-term test to see for ourselves. After the traditional road test of our Sienna was completed, we purchased a new set of Dunlop SP Sport 4000 DSST tires for a tread-life evaluation. The evaluation started at the end of March, 2007, and is ongoing.
We've been checking inflation pressures religiously; aligning the wheels, rotating the tires, and measuring the average tread depth in no less than 16 test points around each tire at nearly every 2,000 miles. Admittedly, most consumers are not likely to follow our frequent alignment and rotation schedule, but we're giving the tires the best opportunity to wear optimally. So far, the results suggest that there are benefits in taking good care of your tires.
After some long vacations stints around Northeast parts of the United States and Canada, we've accumulated just over 22,000 miles. Our comprehensive tread-wear measurements tell us the tires still have plenty of life left. The tires are at least 32 percent worn out and some are closing in on the 40-percent mark based on the fastest wearing groove. Keep in mind that a tire is legally worn out when any one groove depth is flush to the tread wear indicator of 2/32 inch. Our Sienna's tires are showing more rapid tread loss at the shoulders, which is not uncommon for a radial tire, but we also observed a stepped wear condition to the inboard shoulder rib that started to appear around 19,000 miles. In addition, a cyclical tire whine is becoming very noticeable as the miles have accumulated.
We'll continue our put on the miles to see how the wear proceeds, including the step-wear condition.
Related blog posts:
Toyota Sienna AWD run-flat tires wear well for us
Toyota Sienna AWD tires - patience wearing thin
Toyota extends run-flat tire warranty
Toyota Sienna run-flat tires? Spare us.
Run-flat tires go flat with our readers