Solution to wandering on the freeway

My Prius has always had a tendency to wander a little on the freeways. It's been posted here by quite a few. Beyond the basic "check the toe-in and other alignment specs" it was generally agreed that it's just the way a Prius drives.

But after the last set of new tires (Goodyear ComforTreds) it seems worse. I even took it back to the tire shop to have the alignment rechecked, and the toe-in set very carefully. The steering wheel was a little off-center, another common complaint. So they recentered it (to the horizon, not the dash itself). Though it was now centered, and the freeway stability was a little better, it still wasn't really good enough.

Then another symptom... when I hit the brakes hard at speed, the car really darted back and forth. It was VERY disquieting! It almost felt like the car was being tugged one side or another. It took both hands to keep it in the center of the lane. It wasn't the ABS, because it never skid even the slightest. It just didn't want to track straight when braking very hard. This was a safety issue, since the last thing you want when you are braking to avoid an accident is to have to fight the wheel!

So I took it to the dealer, wondering if the recentering had thrown off the electric assist center point, which required the THHT tester to reset. Of course, the tire shop lacks the tester, and even the knowledge that they needed to check anything else.

Well, over the last 80K miles, the three alignments without checking this and other settings really put things out of kilter!

The dealer noted that the following settings were needing recalibration:
- re-align steering wheel angle sensors
- reset three steering torque sensors
- reset yaw-rate sensor
- reset linear valve sensor
- zero calibration (the setting I had suspected)
This was done as well as the four-wheel alignment.

Wow, what a difference! It tracks like it never has before. It's not the most stable car I've ever driven, but the feeling of wandering doesn't start for another 20 mph higher speed than before. I could feel it at 60 prior to the adjustments, and now it's stable at 80. And braking with hands off is straight as an arrow.

This was not cheap. The bill came to $263 (3 hours of special tech, LA prices). I was a little shocked, but it's cheaper than an accident.

It was worth it! The car is far more safe and effortless to drive on the highway fast. It's better in crosswinds, too. It no longer requires such acute attention to steering in order to track the center of the lane.

Whether each and every one of the sensors was contributing specifically to my problems isn't known; they were all out of spec and were all reset. Perhaps a partial job could have been done for a little less labor.

But it solved a problem that I used to think I just had to live with, and was a part of the car's design. But no, it CAN be a joy to drive!

So perhaps it's off to the dealer any time I need an alignment, which is more expensive. But it was false economy to let the tire shop do it, because they are not capable of oding the whole job, and doing it right.

 

No, not a tire issue. The tires the new ComforTreds replaced were identical. It was the realignment done two weeks after getting the tires replaced where the wandering suddenly got real bad, and I noticed the braking issue.

 

After this experience, I don't believe regular alignment shops can align a Prius. They did a 4-wheel alignment after putting on my new tires, but they cannot set center or reset any of the other sensors that guide the VSC system and the electric steering.

Especially if they change the tie rod ends in order to center the steering wheel, they really mess it up.