Re: 2015 SE Premium Tire Wear and Alignment Problem
It's not the "heaviness" of the vehicle that is the problem. There are much heavier vehicles on the road that do not have this issue. It's the setup of the rear suspension and the "nose heavy" nature of minivans. Toyota has designed the rear suspension setup for ride comfort. The downside is the tires tend to wear more on the inside. To get the most out of these tires, you have to rotate the tires every 5,000 miles. Even 10k mile rotations are too long. Yes, alignment checks help but there is very little if any adjustments that can be made to the rear setup.
Putting your tire pressure up to 40 psi on an SE? That ride has to be punishing. When the tires are warm, the psi is likely 43-44. If you have an LE or XLE, consider H-rated tires instead of T-rated (My 2013 XLE calls for T-rated tires which surprised me). The H-rated tires have slightly stiffer sidewalls and may hold up better. Just a thought.
I was happy I got 33K out of the OEM tires. We did have wear on the inside of the tires, not as bad as the OP. I also had an alignment done by Toyota before the new tires were installed. I put Cooper CS5 Grand Touring. I really like this tire: very quiet, good grip and great price. We keep the pressure at 35 psi. I'll report back on the wear of these tires since this seems like a common issue with Siennas.
Good luck everyone.