Highway driving

Get a BT Tech Stiffening Plate for $165.

Wheel alignment can help too. Toyota dealer should check wheel alignment for free if you complain that the car wanders on the highway.

Tire upgrade has been reported by many to make a big difference.


My personal experience, the wandering went away when I installed to BT Tech Stiffening Plate. You can do it yourself. Four bolts, and if you are slender enough and have a good reach, you don't even need to jack up the car.

 

I'm not clear if you've had it aligned or not. If you take your Prius to a Toyota dealer within 12 months or 12,500 miles, whichever is less, and you say your car pulls, you can get a free warranty alignment of the front end. Specification is 0.0° toe. Get a slight, 0.5°, toe-in on both front wheels. Also, ask them for a four-wheel alignment read-out. The four-wheel read-out will tell you if and how far the back may be out. Officially, the rear end can't be aligned. A good independent alignment shop can true the rear up with shims.

Strongly consider replacing the OEM POS (IMHO) tires. While tires are more expensive than the BT Tech plate, the OEM tires have poor wet grip and are noisy, though they are low-rolling-resistance tires. Lots of threads on tire choice here.

You can also read the long discussions here as to the merits of the BT Tech plate, but I agree with NoMoShocks, it makes a marked difference in how the car handles, including curvy roads. It also helps when the bow wave from a big truck passes you, or you pass it.

Some Prius just seem to be touchier than others to straight, constant driving. All of the above will help.

Good luck, it is really a great car.

 

<div class='quotetop'>QUOTE(wanderingBrian @ Jul 12 2007, 11:40 PM) [snapback]477942[/snapback]</div>

I have an 03 Prius and from day one noticed the steering and handling was as close to neutral as it can be. It may be that tweaking caster might improve things. My suspicion is the electronic assist may be part of the problem. I just haven't gotten around to disabling it to see.

On long trips, I find neutral tracking doesn't cause fatigue but requires attention. I had thought about rigging a rotational accelerator (cheap) or gyro (expensive) to provide additional stability input to the electronic steering. But given it isn't fatiguing to me and most of my travel is urban, this remains way down on my list of 'to do.' BTW, it is not a trivial problem, augmenting steering stability, because done badly, it could lead to an ugly stability problem.

Bob Wilson

 

wanderingBrian, welcome to PriusChat.

One thing that may not have been pointed out to you regarding the Prius -

The steering gives very little feedback to the steering wheel. In an average car, if you hit a pothole or other road imperfection, you will feel it in the steering wheel - not in the Prius.

Without that feedback, many new Prius drivers think the car does a lot of wandering . . . of course, with those crappy OEM tires it does to some degree . . . and with its low Cd, crosswinds and passing trucks sometimes aren't much fun either - BUT!!!! - believe it or not, YOU will get better at controlling your Prius with experience. Nowadays, it almost seems like my Prius steers itself. I guess I have become one with the force. :lol:

Since you have already done the dealer alignment thing (twice!) . . . I'd suggest driving a different Prii - either someone you know, or go back to the dealer and do another "test" drive. See if it feels the same as yours.

 

This is another thread that will probably become entirely too long
for all the same reasons as the other ones ... but bottom line, I
would check alignment FIRST, and then worry about bolting on a BT
plate. Yes, there is little or no road feedback in this car, and
it didn't take long for me to move to a more eyes --> hands mode of
feedback when driving. I treat the wheel as a sort of variable
suggestion as to where to point the car, especially at higher
speeds, and tend to turn it at a slow and predictable rate to match
where I want the car to *be* in the next five seconds as opposed to
trying to merely avoid immediate-proximity objects. [That's good
guidance practice in general, of course -- look ahead.]
.
I will say that this is the hardest car to knee-steer that I've ever
had, and that's simply because the visual feedback loop doesn't work
nearly as well with my knee. The more self-centering nature of prior
cars made that easier. I also don't do it often -- just once in a
great while if I briefly need two hands for something, which doesn't
provide a lot of practice at it.
.
Bottom line -- once you're dead sure about alignment, i.e. primarily
toe, don't fight it -- look far ahead and make tiny corrections and
wait for their effect, and you'll find it to be a very smooth
process after a while.
.
_H*

 

Hi Brian,

Welp, the first thing to check is the tires and wheels. Have the car put on a lift, and each tire spun, and each wheel checked for true with a dial indicator. Have the tires inspected for the possibility of a broken or mal-formed steel belt. Check tire pressures. An underflated front tire will cause lots of drifty driving.

Next would be alignment. The Prius toe-in has a specification which allows a little negative toe. Have the alignment set within specification, but in the positive toe-in half of the specification. That is, with the tires slightly pointed torwards each other when the car is static. Other Prius Chat posters have commented that this helps highway drifting allot.

I have been a big BT Tech plate supporter. But I do not want you to go get one, and then bad-mouth it, just because whatever_it_is_the_BT_Tech_plate_does was not the source of your problem. I had no problems on the highway before getting the BT Tech plate, when there was not any wind. The car tracked straight, and while the steering was sensative, if one carefully pointed the car, and held the wheel at that direction, my Prius went straight. The problem I had on the highway with my Prius was with heavy (0 to 40 mph in seconds) side wind gusts. These winds occur here in the spring some years, and are much more common in downstate Illinois. I also had one incident of left turn understeer (not tire traction related). It was like the car was steering itself (I do not have VSC). This might have been due to the road crowning momentum related forces causing chasis flex. The BT Tech plate took care of those problems, or at least reduced them to a point that my Prius is now like driving any other medium handling front wheel drive car.

 

Hey Brian,

Maybe you and I have the worst prius's, but I totally agree with you. I have taken my prius to a terrific alignment guy and told him to put more toe in and the car feels a little better, but still not perfect. I also have a bt plate installed and I'm not totally convinced it helped. I installed 17" wheels and tires which helped in the handling department and decreased my mpg a little. I even bought the TRD Sportivo shocks and springs. They helped the most as far as general handling goes. I think the stock prius is a terrible handling car. With the mods I've made my prius is an OK handling car. The car is heavy and not rigid, which is a bad combination. It's obvious Toyota spec'ed a 0 degree toe in to get that tiny bit more mpg out of this thing at the expense of the handling characteristics.

 

Get the alignment checked. Mine has toe and camber issues on the front and rear. I need to get a more accurate reading on the rear toe (decimal degrees instead of inches) so I can shim the rear. The dealer hasn't been cooperative, so I'm taking it to an independent shop.

 

I used to agree about difficult to keep straight on the road, but now with 7000+ miles on it I don't even think about it.

I truly believe that yes, the Prius is a bit different--and that your mind will eventually adapt to it. Like eyeglasses--when they're new things seem a bit weird, but after a day or two the weirdness is gone. Your mind adapts to it.

 

I've not experienced any real issue with wandering, buffeting or crosswinds in my 07 base Prius, even though after reading a number of threads on here before I bought it, I was expecting problems. Last weekend I came back from a 1000+ mile trip, almost entirely on interstates, and found the car to be amongst the most relaxing to drive of any I've had. It was affected by heavy wear in the road surface at one point, where distinct ruts caused it to wander in the same way my last vehicle did in the same location, and I could feel the 'bow wave' of some of the larger trucks a little more than I have previously been accustomed to, but that was about all.

I realize the above doesn't help in terms of diagnosing the problem, but it does suggest to me that it's an issue which varies with the specific car and which should therefore be readily resolvable.

 

I agree 100%. Once I became accustomed to the car's handling, it became as easy and comfortable as my Lexus to drive.

 

If you have good tires (not the OEM POS) and the alignment checks out, then it's almost certainly pilot induced oscillations. Most of the tracking problems with the Prius come from the zero-deadband steering with almost no feedback. Drivers tend to over control, leading to oscillations. Your considerable previous driving experience will work against you in this situation, since the Prius steering is unique. I find the Prius to be more like my experience with airplanes and boats. It takes a very light touch; just think about steering corrections, with control inputs more a matter of pressure than displacement. It gets easy once you are used to it.

Tom

 

<div class='quotetop'>QUOTE(chuck_k @ Jul 15 2007, 11:11 AM) [snapback]479131[/snapback]</div>

Same here, no problem whatsoever and no mods of any kind. Goes straight as an arrow. I hit a curb once with the front left tire and thought I'd need an alignment (after reading here about problems), but it still goes straight. I've also never checked the tire pressure for 3k miles, so I don't even know what it is. There must be something common to the cars with the wandering problem... front suspension member out of spec or something. If there is a place to research the problem... this is it! You might also want to trade Prii for one day with another Prius owner and see if there is a noticeable difference in handling. You might even get the dealer to let you borrow a new one for an hour to see if there is a difference.

 

Zero toe-in is allowed by the spec, but may be the cause of that uneasy feeling. Did they give you a printout of the alignment they did? You may have to specify toe-on to them, or they may leave it at zero.

Torsional loads at the location of the BT plate are probably almost nonexistent at highway speeds while driving straight, so I doubt that will solve your problem.

I'd like to hear from an experienced alignment shop about the choices in alignment Toyota made. Speculating, perhaps in an attempt to get better mileage, they chose a low friction design (say with less caster and king pin inclination?) which would create "less resistance" which is another way of saying "allow wander" since the self-centering action of some suspensions necessarily involves more resistance to turning, even at the slight turn angles used on the highway.

 

As a 90 mile a day commuter, I've never had issues with straight line control, even in our Santa Ana winds, which are severe where I drive. As a previous 66 Mustang owner, the Prius steering has no "freeplay" at all, which is great. My rememberance of the Mustang, is about 5 or 6 inches of steering before the car even moved from straight. If that's the kind of steering you are used to, the Prius isn't it. I much prefer the more direct connected steering than the dial and pray of my old Mustang. You are doing all the right things. My car is totally stock, never been aligned, and has 38,000 on the half worn OEM Goodyears, that feel Ok for me in sunny dry LA. I did add a BT plate, and run the TPs about 42/40. I find the traction OVERcontrol oppressive, but no issues at highway speeds where I spend 10 hours a week. Maybe the Prius just isn't your kind of car. (BTW, I'm 58, so I don't think it is an age thing.)

 

<div class='quotetop'>QUOTE(KTPhil @ Jul 16 2007, 12:32 PM) [snapback]479748[/snapback]</div>

I just had my alignment checked again at a tire shop after the dealer alignment was done on 7/3. The dealer reported the front toe-in as Zero on both sides; the tire shop reports it as slight toe-out on both sides. My understanding is that a front wheel drive car will tend to "pull in" on applying torque to the front wheels and will toe-out due to force against the tires when coasting.

My rear toe is still out of spec, even though the dealer gave me a printout showing that it was "perfect"

http://priuschat.com/index.php?showtopic=3...mp;#entry479783

 

I have to wonder how much slop is supposed to be in the suspension... if acceleration can change toe, that means there has to be play on the steering and/or suspension that gets taken up by accel/decel forces. I have to wonder in a new car whether there is really this much play, and furthermore, how much force is applied when cruising at an even speed as this poster wrote about.

Suppose there IS a lot of play. Then at steady speed cruise, the forces are changing from slight accel to slight decel as you (or the cruise control) try to maintain a constant speed. Is that gentle accel/decel really enough to cause wheel alignment changes? I really don't think so, but if there is, perhaps that changed form toe-in to tow=out is causing the wandering. A little more toe-in (as recommended by many here) would mean it changes from a little to a lot of toe, but in any case it would retain SOME toe-in so that it would track straight.

 

My 2007 prius PKG 2 has 4700 miles so far, it does exact the same thing driving on the highway. The car just pull to right or left, especially on poor highway road condition. So far average 48MPG combine.

I won't bother to do alignment, replacing with better tires, adding stiffing plate etc......Just drive it and enjoy the good MPG.

My 2007 prius PKG 2 has 4700 miles so far, it does exact the same thing driving on the highway. The car just pull to right or left, especially on poor highway road condition. So far average 48MPG combine.

I won't bother to do alignment, replacing with better tires, adding stiffing plate etc......Just drive it and enjoy the good MPG.

 

Since buying my 2007 Prius, I've had to cock the steering wheel slightly to the left in order to maintain a straight line -- I always thought that was odd. The car didn't "pull" per se, because once I cocked the wheel the car would drive straight hands-free and not pull in either direction.

I had the dealer check the alignment, they said I had a toe alignment problem and they fixed it. Since then, the steering wheel is straight as an arrow. I can say I notice a litlte bit of improved straight line driving, but that could just be a placebo effect.

I recommend you have your alignment checked.