Poor steering and handling on the highway.

FredWB,
I am a new Prius owner 800mi 05' and find exactly the same issues you describe wandering etc. I too find this unacceptable and was initially hopeful performance rated tires would help but it sounds like they won't.
I am going to get my alignment checked and try what 200Volts outlined.


200Volts,
Thanks for your complete description and photos I'll try it to see if it helps.


wanderingP

 

[font=Lucida Console:8376ad8b8c][/font:8376ad8b8c]I've had my 2005 about 6 weeks, and my wife and I have both noticed the unsteadiness, especially at highway speeds, that is more pronounced under windy conditions. The latest auto issue of Consumer Reports referred to the tendency as a downside in its review of the 2005 Prius. After reading the thread, I intend to have the dealer check for alignment problems.

Salsa Red, 1800 miles, Package 6, average ~ 44 mpg

 

CR has their own automotive shop. If an issue comes up, they first check to see if everything is set to factory spec, then retest.

My toe and camber were both off. The alignment helped a lot - it was free at the dealer - but the Prius is not the most steady highway cruiser out there.

My parents have a 2003 Buick LeSabre Celebration Edition and under similar highway conditions it's rock steady. It tracks like on rails.

Magazine testers who have reviewed the Corolla with electric assist power steering have made similar comments. Maybe the EPS is too sensitive. Combine that with a car with very low Cd and a tall, narrow profile ... you get the idea.

Changing tires didn't help me. I went from the stock Goodyear Integrity to Michelin Harmony with no real difference in highway tracking.

 

jayman
How do you like the Harmony tires. I'm considering a change.

 

Compared to the OEM Integrity: much quieter, somewhat better ride (Softer), better wet traction, no difference in highway fuel economy that I can detect.

As far as snow/ice traction: like any all-season tire, don't even *think* about it. With the very sensitive Traction Control on the Prius, it would leave a green light at an icy intersection no faster than a walking pace. I even got stuck going up an icy parking ramp once, the car just came to a stop with my foot right to the mat.

If you live in a part of the country that gets "real" winter conditions, I really have to recommend proper winter tires. I would never drive on all-season tires as their traction is subpar. Especially in temps -20 C or colder, it's like driving on racing slicks.

Another point to consider if you have "real" winter driving conditions: do they salt the h*** out of the roads? If the answer is "yes," you want steel rims for the winter tires.

The steel rims are easily painted with a spray bomb once they start to rust. Once nice aluminum rims start to oxidize, they look *very* ugly and it gets $$$ to fix.

 

I live in the southern US so snow is rarely seen. It does get icy a few times a season, but not really concerned about that. More intrested in ride comfort. Thanks for the info!

 

Sounds like you don't have to worry about a winter tire.

If a nice soft ride is of upmost importance to you, a lot of folks like the Goodyear Assurance ComforTred.

Goodyear claims it has extra absorbtion built into the casing. I might consider it for a 3-season tire if the roads here get any worse. I hit a frost heave this morning that just about knocked me off the road.

 

I, too, took a little while getting used to the Prius' handling. But this wandering is something different. If permitted a little intuitive licence, I would say the problems are aerodynamic. Having read all the posts so far on this subject, I would say 200volts has the best idea. With his racing background, he has a good understanding of the forces at work. The car is basically acting like a big wing, and the faster it goes, the more lift is generated. This causes the steering to lighten and become twitchy, and makes the car more sensitive to crosswinds. There are so many variables involved (car speed, wind speed and direction, road surface, cargo placement, etc) that no two cars will behave exactly the same. A possible solution is to reduce the airflow beneath the car. Even small changes can have big results. Try mounting the licence plate under the front air intake instead of on the bumper. Move the little chin whisker air dams, as 200volts suggests, or build a bigger one. Some cardboard and duct tape will work fine as a temporary experiment. I have also seen flexible vinyl baseboard used to good effect. If that works, have a bodyshop attach a chin spoiler. Any slight increase in drag or fuel consumption is worth keeping the front end on the ground. The Prius is very slippery underneath, which is great for a low coefficient of drag, but it would seem the designers paid more attention to drag than to lift. Perhaps if Toyota's Formula 1 people spent some time in the wind tunnel with the Prius, a solution could be found.

 

What are the allignment specs for the Prius?

I don't want to be stupid, but I've scanned this thread a number of times and thought I saw the specs for Prius alignment, but I could be wrong.

Can somebody refresh my memory, or tell me which thread or in what thread are the specs for the alignment?

I've scheduled a time for my dealer to do an alignment under my 12/12,000 adjustment period for a steering wheel that is pointing right a few degrees. I posted a different thread on this one already.

 

I think the alignment numbers were lost when priuschat went down. I can't find anything old for these stats. Here is what someone posted for there feedback:
http://www.priuschat.com/forums/steering-w...ent-vt6867.html

 

Thanks, very helpful. I have my car at the alignment shop my dealer uses and they say it was done. The vehicle's toe was correct. They way the rear is off, but there are no adjustments, as the other thread indicates, however I doubt that it is really off. I wish more dealers had their own racks rather than farming out this type of stuff to tire shops. Thanks for the link, 2 points to you from my paltry number of points now.

 

I just got mine aligned and the back right was 0.38 + toe out. My left rear was 0.02. The Prius spec shows my right rear has about 40% extra toe out.
I discussed this with my service manager and they are can get a shim kit to adjust this (major work, they take apart the suspension).
I am aking them to do it under warranty work, since this is preset at the factory and I have not crashed the car, etc. I am way past the 12/12k that would cover this under warranty. They will get back to me in about 3 days.

 

See my front air dam mod (15 minutes, nothing to buy) at :
http://www.priuschat.com/forums/next-vt490...r=asc&&start=80
This made a bid difference in my 75mph crosswind stability.

Get front and REAR alignment checked. I had 40% extra toe OUT on one rear wheel (dealer can only adjust with a shim kit).

 

After reading this thread, I was wondering about the wandering and paid close attention to it, as I too have wandered at times. What I have discovered in my case was that the car does just fine at up to 70 mph, the top I have done, as it is a new car for me, still under 1,000 miles. However, when the car has wandered on the highway I discovered that it had more to do with me trying to recall what button does what on the steering wheel or around the MFD. Hence, I am letting my concentration wonder! New toy, new gadgets. I now take real care with learning one button at a time, and do not look at the wheel, and keep my attention on the road. Any thoughts on this?

 

Kudos to 200Volts - My car had a very noticeable, but not extreme case of instability at highway speeds. I tried his airdam mod, and it made a huge difference for me. We had to take a 2500 mile trip shortly after, and my Prius was as stable as any other car I've had. That was with the OE tires. During the trip, I had to replace the tires due to the mother of all potholes. I bought Traction TA's, which were highly rated by Tire Rack. After 37k miles on the Goodyears, it was a welcome change. My car is steady as a rock, even above 90 mph ( :mrgreen: don't ask where!) The spoiler mod gets credit for this - I agree with 200Volts. Thanks.

 

Thanks. What I think is happening to the aerodynamics is that there is buildup of air pressure under the front bumper to wheels area. Since it is completly sealed up the air lifts the front of the vehicle. The original spoiler location traps more air after it is under the car. Look at it from the side and picture a cup on it's side, moviing in the direction of the open end of the cup.
My new spoiler location pushes air to the side, creates a high pressure zone closer to the front of the bumper and allows more air to escape in front of the wheels (the original dam could actually push air under the car, especially from a cross wind).
Raising the tire pressure on the front tires will aggravate this more since you are raising the front slightly and changing the angle of attack.

I'm working on a real fix to this problem (full width spoiler).
FYI: If you compare the Prius to the Ford Focus you see they have almost identical dimensions (and Focus owners complain about stability and tires-tire pressure sensitivy also).

 

I tried the air damn mod and experimented with lower tire presures as well. I even tried the rubber baseboard material, but it's a little bit wimpy for this purpose. Then after driving for awhile I took them all off, lowered the pressure (37/35) and drove that for awhile. Then I increased the pressure to 42/40. Overally I'd have to say the air damn experiment improved my car's stability the most. I'd be interested in your long term solution 200volts. I think I'm going to construct something out of ABS or Acrylic which will be 2-3 inches deep and span most of the front, leaving the existing dams where they are. I looked at the new Acura TL and that's what they've got. Wish I could get a dam like that cheap!

 

Be careful if you add anything to the front end that is lower. You will drag on driveway entrances and parking curbs. Moving the air dams forward does this SLIGHTLY right now. They are very bendable so this is not a problem, but a rigid material would break or tear at the mounting hardware-locations.

 

How much is that import chin spoiler part? Would it deal with this issue?

 

If it's the one I've seen it doesn't look to be very functional and sits up too high. But the curb issue is an important one and a stiff rubber dam would probably work best