Unstable at higher speeds

[sdcruiser]

Yes I meant 60 not 50 for those tires, a typo, sorry. Although I only have about 50K miles on my 2004, and have had a few different tires on it, I have not worn any of them down except for some alignment issue that wiped out on hydroedge tire. I drive sanely enought to get 48-49 mpg in a short 10 mile commute with lots of hills. I just kept searching for better handling and tried lots of combinations including the disaster that was the Scion take-offs. Nice wheels but mileage went down the tubes they were so heavy and wide.

I would have/should have left the hydroedge tires on but I wiped one out when the alignment went crazy and I didn't catch it. Funny because this car has been aligned by more experts around town as I sought better handling so it was during a 6 month period where I didn't try a new alignment guru, lol.

So when I say the car doesn't handle, I'm not talking slalom or anything. Just straight line stuff when you either encounter lots wavy deep and sometimes new rain grooves, or large passing vehicles, or 20 mph cross winds thru the mountains. That's where the car will literally just jump 6-12" suddenly from a side force. My wife sees and feels it without any wheel motion from me.

Yeah the cars medocre handling stability is probably acceptable to some and I can see if you're not riding on a lot of grooved cement or unblocked cross-winds you might think the car is just fine. I did find out that the touring frt struts and springs (not sure about the springs) are standard after March 2005 Prius and that there's a different covering/spoiler under the engine on later models that could help with the handling. I did do one mod that seemed to help more than tires and that was using rubber wedges to stiffen the front coils. I took them out when I suspected an issue with my hydroedge wear. Now I see there are lots of stiffer springs available but they all seem to lower the car.

Another mod I did back in 2004 was that I added an air dam at the very front of the car all across the bumper. While it was not really ideal for aerodyamics it did reduce lift and made the car track better. I probably should not have given up on persuing that because it didn't seem to affect mileage at all. I have played the tire pressure game to infinity and know about the 2 psi difference as well as trying higher differences. The car is now pretty bad with these Falkens so not much is going overcome that. They exaggerate the effect of road grooves even more. They are the only tire I've found that felt more stable at higher pressure, like 42/40. All the others seemed better at normal pressures where the contact patch was not reduced.

So out of all the suspension parts and other fixes available, I'm curious which ones worked the best with owners that complained about wandering and straight line stability?

[tomcornell]

Originally Posted by sdcruiser

So when I say the car doesn't handle, I'm not talking slalom or anything. Just straight line stuff when you either encounter lots wavy deep and sometimes new rain grooves, or large passing vehicles, or 20 mph cross winds thru the mountains. That's where the car will literally just jump 6-12" suddenly from a side force. My wife sees and feels it without any wheel motion from me.

My 2007 Prius has done this from the time I drove it away from the dealer. I mean I could set the speed control and lock both my knees solidly agains the steering wheel--it would lurch right, then lurch left, but NEVER track in a straight line. Borderline dangerous in my opinion.

I took it back a few weeks after purchase asking for an alignment. The female tech took it for a test drive with me on a dead straight road and noted no wander, nor did I. (Of course it had to make a monkey out of me!) So they did not want to perform an alignment on it. She mentioned that being a light car with a high profile, it would suffer the effects of crosswinds more than other vehicles, but it does it in dead calm on newly paved highways as well.

I'm going for new tires Monday and will get a full alignment as part of that process. Between getting rid of the crap rubber that came with the vehicle and the alignment, I expect it to hold a straight line better.

[brick]

Ask for a before/after printout of the alignment and post the values here. Some cars have trouble with the rear alignment, and alignment shops generally don't touch that. That problem has to be corrected with shims. The only way to know is to compare your values to the specs to see where they fall.

[tomcornell]

Originally Posted by brick

Ask for a before/after printout of the alignment and post the values here. Some cars have trouble with the rear alignment, and alignment shops generally don't touch that. That problem has to be corrected with shims. The only way to know is to compare your values to the specs to see where they fall.

Although I haven't gone back and checked yet, I distinctly recall some earlier posts in this thread stating that the rear axle on the Prius is solid and can not be adjusted. Essentially it comes fixed as-is from the factory. I believe this had to do with a discussion about what unscrupulous service departments try sell you, whether you need it or not.

Come to think of it, I probably saw that in the "what you need, what you don't" maintenance thread.

It certainly would be nice to have the definitive, unequivocal answer to this once and for all. What does the shop manual say?

[dogfriend]

Originally Posted by tomcornell

It certainly would be nice to have the definitive, unequivocal answer to this once and for all. What does the shop manual say?

The shop manual says that the rear alignment is not adjustable. However, I had to shim the right rear hub on my car to fix the toe in. Your symptoms sound like my car before I fixed it.

More details in this thread:

2007 Model Alignment issues

[sdcruiser]

Originally Posted by tomcornell

My 2007 Prius has done this from the time I drove it away from the dealer. I mean I could set the speed control and lock both my knees solidly agains the steering wheel--it would lurch right, then lurch left, but NEVER track in a straight line. Borderline dangerous in my opinion.

Sometimes I either want to cry or just laugh at all of this. Tom obviously is experiencing what I've been "ranting" about since 2004. And then someone will chime in as if we've never owned a car before and say something like, you must be gripping the wheel too tightly...or my car is rock solid up to 105 mph!

Our cars are almost dangerous at times and Toyota either can't or won't listen. My opinion is that if they acknowledge this, they leave themselve open for litigation so they just go on denying it and force us to search all over the place for solutions that probably don't exist. My car is now better thanks to later model frt struts and touring edition anti-sway bars. It's still not what I would call good, but it's improving at my expense ($650 this time). Now I'll be shelling out for yet another set of tires because the Falkens accentuate all these bad characteristics of my car. So my $28K (plus another $2k in "improvements") car still handles worse than the $10K crappy Kia I rented this weekend. I'm not kidding. That cheap car tracked better than my $28K Prius. A lot better.

[tomcornell]

I took my 2007 Prius to a local shop that seems savvy. The printout shows the right rear wheel toe-in wayyyyyyy out of spec, which accounts for the screwy driving pattern of this vehicle. See the attached scans.

Unfortunately, they need to order the square shim kit for the rear axle and I need to take a trip in the car before it will come in, so more damage to my new tires will ensue.

At least now I know for sure what has been going on, and the dealer was backpeddling from giving me a free alignment. At least when I return it will be done properly.

[dogfriend]

Originally Posted by tomcornell

I took my 2007 Prius to a local shop that seems savvy. The printout shows the right rear wheel toe-in wayyyyyyy out of spec, which accounts for the screwy driving pattern of this vehicle. See the attached scans.

Yours is similar but a bit worse than mine was. I couldn't get the dealer to fix mine either.

[tomcornell]

Originally Posted by dogfriend

Yours is similar but a bit worse than mine was. I couldn't get the dealer to fix mine either.

I forgot to add that she recommended that I get the tires rotated halfway through my trip so that the they don't learn the pattern of this poor alignment. Since I got new tires at Costco that should be no problem for me. I knew the stock tires that came with the car were crap so I wasn't as motivated to investigate it further at the time. I wish I had acted sooner, though.

I'll post the results when the shim kit comes in and I get back to take the car in.