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Since buying my 2002 Prius in December I've been on the interstate a few times and have been dissapointed with the handling above 55 mph.
I have had the alignment checked and front and rear wheels are both slightly toe in and the tech said he didn't think he could adjust it any better. I've also experimented with a myriad of tire pressure settings. Things are better at lower tire pressure but the problem still exists.
I've recently done some reading in the Prius New Car Features book and I've come up with a new theory. I've attached the relevant page from this book to this post.
The rear suspension of the Prius contains toe control links, trailing arms, an axle beam, and a series of bushings. The idea here is to correct rear axle toe when cornering. The book gives an example of how a right turn can cause the left rear wheel to toe out. This is a bad thing that should be prevented when cornering. Toyota has implemented rear axle toe control to solve this problem. Toyota says this problem is solved by a toe correct function that utilizes the lateral force during cornering.
I understand how this is beneficial during lateral forces encountered during cornering.
I'm thinking about what happens when lateral forces are encountered on the straightaway. Examples include crosswinds or the tires encountering ruts in the pavement. In these situations it seems like the rear axle toe control would be undesirable since we want the Prius rear wheels to continue tracking straight ahead. It seems to me the lateral force is going to confuse the rear suspension into thinking that the Prius is cornering when it has merely experienced a crosswind. I think this could be the explanation for the squirrelly behavior I've experienced on the interstate.
I can imagine a scenario where a gust of wind would try to blow the Prius from left to right across the lane of traffic. This lateral force will induce forces on the toe control links and trailing arm bushings of the rear axle such that the the rear wheels will tend to steer in the same direction that the wind is blowing the Prius. This has an effect of making the crosswind seem much bigger than it is in reality. One can come up with a similar scenario navigating the 18 wheeler ruts that are a standard feature of Idaho interstates and highways.
Does anybody know if the Prius rear suspenion toe correct function is adjustable? I'm guessing the answer is no.
Thanks,
Ed
I have had the alignment checked and front and rear wheels are both slightly toe in and the tech said he didn't think he could adjust it any better. I've also experimented with a myriad of tire pressure settings. Things are better at lower tire pressure but the problem still exists.
I've recently done some reading in the Prius New Car Features book and I've come up with a new theory. I've attached the relevant page from this book to this post.
The rear suspension of the Prius contains toe control links, trailing arms, an axle beam, and a series of bushings. The idea here is to correct rear axle toe when cornering. The book gives an example of how a right turn can cause the left rear wheel to toe out. This is a bad thing that should be prevented when cornering. Toyota has implemented rear axle toe control to solve this problem. Toyota says this problem is solved by a toe correct function that utilizes the lateral force during cornering.
I understand how this is beneficial during lateral forces encountered during cornering.
I'm thinking about what happens when lateral forces are encountered on the straightaway. Examples include crosswinds or the tires encountering ruts in the pavement. In these situations it seems like the rear axle toe control would be undesirable since we want the Prius rear wheels to continue tracking straight ahead. It seems to me the lateral force is going to confuse the rear suspension into thinking that the Prius is cornering when it has merely experienced a crosswind. I think this could be the explanation for the squirrelly behavior I've experienced on the interstate.
I can imagine a scenario where a gust of wind would try to blow the Prius from left to right across the lane of traffic. This lateral force will induce forces on the toe control links and trailing arm bushings of the rear axle such that the the rear wheels will tend to steer in the same direction that the wind is blowing the Prius. This has an effect of making the crosswind seem much bigger than it is in reality. One can come up with a similar scenario navigating the 18 wheeler ruts that are a standard feature of Idaho interstates and highways.
Does anybody know if the Prius rear suspenion toe correct function is adjustable? I'm guessing the answer is no.
Thanks,
Ed