Unstable at higher speeds

As expected...

Insults are the last refuge of the beaten scoundrel with a failed argument.

You stay classy, Shawn Clark!

 

Dobey,

I can't see what you hope to accomplish by continuing in this vein. You've effectively been arguing against your own statements. And we are supposed to be impressed by your display of intellectual confusion/dishonesty? When were you being honest and when were you obfuscating/being hard headed? It's tough to tell without a scorecard.

Double blind testing would be nice and all, but what is the point? Even you have claimed the stiffening makes a difference in the ways I and many others in this thread observed, then you argued vigorously that theoretically it does not, cannot and therefore all my observations and others are the result of intentional prejudice. I'm not sure what we are supposed to make of this other than you are a very confused individual.

 

I've put over 10,000 miles on mine & do have 60 series tires, but the rest is "stock". I have the stiffening plate & strut brace to install, but not on yet. I think a lot of the sensitivity is exhacerbated by over correction. Just my opinion as I have done it myself. Given that, I've had mine to 108 mph, steady as a rock.

I find if you look out at a distance it will help prevent over-correction. Works the same as landing a plane. If you get to fighting it & micro-manage, you will not establish of smooth glide & no smooth landings in sight. Look out there a ways & let it be. Works for me & hope that helps someone.

 

I'm jumping in and not reading the rest of the fodder in this thread.

I'm amazed you pushed 108. I've pushed my [former] 05 to 102 mph and it was squirrely. Never tracked straight. Passing semi's takes you several feet off course... And the noise was terrible.
I've pushed my current vehicle to 120 mph and felt like it was 70 mph in the Prius (same stretch of road).

 

The governor kicked in at 107-108 and that was it. I'm guessing the Prius would probably hit 115 or so with no governor. I drove several miles, hills, curves, guiding with finger and thumb. I noted mileage still in the 20's. I'd get mine aligned & evaluate my tires if I were having problems. It's certainly not a race car, but not bad either.

 

Since I did the BT stiffening plate and the front strut tower brace the majority of the squirreliness is gone. I've been back over my test stretch of interstate now in high cross winds (~30 mph directly perpendicular) and it is MUCH more tractable. There is still wind buffeting around semis and such (as with any vehicle), but the vehicle tracks better than in stock form, so it's not hairy passing anymore. As part of the drive I observed other vehicles catching gusts as they passed beyond wind shadows, noted their apparent deflection, then observed my own which was similar. This was a noticeable improvement compared to before the stiffening components.

I did have the opportunity to do a bit of higher speed driving recently and was pleased by the feel of the car compared to stock. It wasn't really cut out for this before the upgrades.

 

I've been away from this forum for awhile but still have my 2004. I've been to virtually every alignment guru I could find, discussed my car with several dealers, tire experts and with some of you online. Here are my most current observations. My best handling experience was with the stock size Michilin hydroedge tires, BT back brace, and rubber wedges in all the coil springs. The stiffening of the braces reduced a lot of the response of my car to outside forces, winds, grooves, road camber, passing trucks.

I removed the wedges and installed Falken 19550X15 912 tires. This is by far the worst my car has ever handled. And it gets about 5 mpg less. I just returned from a Vegas trip and both my arms hurt now from trying to stay on the road. My wife can easily feel the car moving around without any steering wheel input from me, it's that noticeable abrupt. It's a squirrley hair raising ride at times. I had a truck wander into my lane at the same time my car "jumped" to the left, probably a cross-wind. And it was very close to a bump with him. I'm running max toe in now after the tire dealer insisted on zero toe-in. That was even worse.

I can't help but think that we're talking about two cars throughout the "handling" threads I've read. One car has mediocre handling but adequate for the owner and the other cars are a disaster. And so the average or mediocre handling car owner thinks the rest of us are nuts that don't know how to drive. It all gets pretty insulting at times because I know my wife's Acura RSX handles light years better than my Priius and I've owned dozens of cars, all handling much better than my Prius. So my conclusion, based on my mechanical engineering background is that it gets down to a tolerance issue with our cars. It's basically an average to mediocre handling car given the suspension/weight/aspect ratio/aerodynamics and that those of us experiencing the worst handling have cars that exhibit worst case tolerances. It might be softer springs, less rigid body, slightly looser suspension components, extreme but in tolerance alignments. We'll probably never be able to make that right, but we can make it worse or slightly better.

Even the Ford Focus I rented on a recent trip was a "stellar" handling car compared to the most expesive can I ever bought, my Prius. If I thought that spending $2K or more would drastically improve my car I would gladly spend it. As it stands now I'm going to get this Falken tires off the car and take a bath on that. My tire dealer says Pirelli P4's should be a lot better. Anyone have experience with those compared to Hydroedge? I hate to get another tire on this car that catches road groooves like this one.

The other thing I'm considering is having the camber adjusted from about -1.5 deg to around -0.5 deg in an effort to improve straight line stability. Anyone ever try this?

 

Negitive Camber helps stability in the turns. It hurts straight line stability since there is less contact with the road when going straight. Our car comes from the factory with oversteer issues at highter speeds (45+) Cheepest fix is to run highter presssure in front tires vs the rear. Try a 2lb difference 1st(42f/40r) then try a 4 lb difference42f/38r). This will help. Let us know which one you liked better. Very few cars come from any factory with oversteer issues. It is uncorfortable and you can get into trouble quickly due to snap oversteer. Stiffer front anti roll bars are used effectively to keep oversteer in check on sport/race cars. I have JDM one on order from Bullitproof. It is not a cheap solution.

 

Two different kinds of drivers rather than two different cars. I understand what you are saying on the handling side, that was the negative of the vehicle. The strut tower brace and stiffening plate make the handling acceptable to me, but it trails my previous rides considerably in this dept.

You could match the same drivers up to typical tire choices in other vehicles. Whenever I hear someone say, "I only got 50,000 miles out of that 70,000 mile tire" I pretty much ignore their tire recommendations. It's not that I think there is anything wrong with them, just that they don't drive like I do and I would probably hate any tire they recommended. The primary consideration for me is not how many miles I eke out of a tire, but how well the vehicle corners in the wet and whether or not the tire results in white knuckle rides after 10,000 or 20,000 miles when it rains.

 

sdcruiser,
Did you mean 195/60 r15 (not 50) ?
I just put those on both our 07s. I think the ride and stability are very good, mileage down 1-2 mpg.
This is compared to the OEM intergrities.
We have not had the same handling problems as some have had.
Carl

 

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?

 

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.

 

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?

 

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:

http://priuschat.com/forums/gen-ii-...ooting/33373-2007-model-alignment-issues.html

 

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.

 

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.

 

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.