Our 2004 Toyota Prius is wearing a brand new set of tires. The last set was badly worn, and the wear had grown uneven, over time. One had been driven on flat (or very low) long enough to score the inner and outer sidewalls. It was time.
The original Goodyear Integrity OE tires never got much love from our cadre of test pilots, so we wanted to try something different. Our choices were many because a lot of companies, Goodyear included, have brought out new "green" second-generation low rolling resistance tires for the Prius, each claiming more grip, shorter wet stopping distances, the same or better ride, the same or better noise and perhaps even a little less rolling resistance than the original rubber.
I was leaning toward the Bridgestone Ecopia, one of those new "green" tires. The final decision became simple because my local Bridgestone dealer, the one next to the Autozone where I dispose of my waste oil, was open this past Saturday, had them in stock and could do it in an hour, right then and there.
Done and done. The Prius had new shoes before I had lunch.
Furthermore, as I'd speculated, the new tires cured the Prius' steering wheel misalignment and ESC problems, single handedly and immediately.
Without so much as touching the suspension, the new Ecopias brought the wheel back to dead center when driving straight. The pull is gone. It's back to square.
Meanwhile, back at the scene of the original crime, the ESC system no longer fires when it's not supposed to. No flashing lights, no piercing piezo screech. It's cured.
I'm not basing that proclamation on just one corner -- far from it. Last night, I loaded the family into the Prius for a trip to Trabuco Oaks Steakhouse, some 25 miles distant. And I made sure to take the back way up Santiago Canyon Road, passing Silverado and Modjeska Canyons to Cook's Corner, where we finally turned left onto Live Oak Canyon Road. It's all two-lane, and the route is as scenic -- and as twisty, in places -- as the place-names suggest.
There were no problems at all. The steering stayed centered, grip was good, the ride was smooth and it may even have been a little quieter than before. Most of all, the ESC system never let out the slightest piezo peep, whether turning left or right.
Moral of the story: If you're having problems that seem to be alignment-related, have a look at your tires before you do anything else. If they're worn down to the point where replacement is imminent, go ahead and get new ones and see how things change before you decide to run off to the alignment shop. You might find that your problem disappears, like ours did. This is more likely in the case of many strut-based cars like our Prius, which has no alignment adjustments except for front toe-in. Without a healthy curb strike or accident to bend something, things can't go very far out of spec.
Tire conicity, on the other hand, can develop over time for a number of reasons. Conical tires, in amounts too small to see, can cause the steering to pull to one side if the concity isn't balanced (equal and opposite) across the left and right sides of the front axle. If you don't want to re-zero everything with new tires just yet, you can check for this yourself by swapping the front tires left-to-right. If conicity is the culprit, your steering pull should switch to the opposite direction. It may even disappear for reasons that get complicated enough for a full-length article.
This is not intended to devalue wheel alignments--they can be very important, especially on cars like the first-gen Miata, which have double eccentric cams on their lower control arms, front and rear. Because they are so adjustable, they can move about more easily, too. Still, unless you know your problem is a direct result of hitting something, have a go at the tires first, then have it aligned if there's still any doubt.
As for the Ecopias, we'll see if we can take them out to the track once they've got a few more miles on them.
Dan Edmunds, Director of Vehicle Testing @ 84,643 miles
bodyblue says:
11:58 AM, 09/27/10
Dan, It sounds like your Prius has been beat to death with little love and care over its lifetime at IL. Why are some cars treated so differently? It became filthy inside.....had tires that needed replacing long ago....why? Is it because it is not an exciting car? So boring cars are not deserving of tender loving care?
This is a serious question and I hope you give a serious answer.
wobbly_ears says:
01:09 PM, 09/27/10
@bodyblue,
It's not the personal car of the editors. Since they didn't pay for it, they treat it worse than the rental car.
It's a miracle that the Prius hasn't fallen apart under their 'Care'!
sodaguy says:
01:15 PM, 09/27/10
How much were the tires?
Although the tires "cured" the ESC problem, wouldn't an alignment check still be a good idea in case to ensure that you do not cause any unneeded wear to the new tires? As you are probably aware, it is possible for a car to be out of alignment even if the steering wheel is straight.
bodyblue says:
01:31 PM, 09/27/10
"It's a miracle that the Prius hasn't fallen apart under their 'Care'!"
More like it is a testament to Toyota durability. My wifes Prius has been flawless. I take good care of all my cars...high performance or not...unlike IL.
actualsize says:
01:55 PM, 09/27/10
Sure, sodaguy, that's certainly next, for peace of mind. But the only "alignment" adjustment possible on this car is front toe-in. If the steering wheel were to be perfectly centered, as it now is, then toe-in would have to be equally "out of spec" on both sides, a very unlikely situation. I'll tell you what I find, but I don't expect to find anything. If this were my own car, I'd skip it.
The Bridgestone Ecopia EP100 tires were $88 each, plus tax and fees. They're 185/65R15, with a higher load and speed rating of 88H. The original tires were P185/65R15 with a lower load index of 86 and a lower "S" speed rating. The Ecopias would have been $78 each online via tire rack, but I didn't want to wait and then hassle with scheduling a fitting somewhere during the work week. My local store had the tires and the time while I was standing there, and that was worth $40 extra to me.
The higher load and speed rating is directly related to that leading "P" on the size. It's fine going this way, where the lack of a "P" on the new tire raises the load rating, but if your car's standard size does not begin with "P", going to a P-metric replacement tire will lose you a point or two of load capacity in most cases.
Tirerack ignores the "P" for some reason, but they shouldn't. When you shop online with them, you must be careful to check the numerical load rating to make sure it's the same or higher than your car's original requirement.
P-metric sizes are based on a US Tire and Rim Association (USTRA) standard. Non-P sizes are most often based on specs published by either the European Tire and Rim Association (ETRTO) or the Japanese Auto Tire Manufacturers Association (JATMA). The latter two entities specify more stout construction guidelines for a given tire size, so they usually provide one or two points more load capacity.
ptcdawg says:
02:07 PM, 09/27/10
Good tires can make a car for sure.
bodyblue says:
02:08 PM, 09/27/10
"This is a serious question and I hope you give a serious answer."
Guess that was a vain hope.
abuddy82 says:
05:25 PM, 09/27/10
Do us all a favor put the car on the rack and check the alignment, I’ll bet it’s not in spec.
bodyblue says:
05:42 PM, 09/27/10
Dan, I did not think you would answer my question, but I hoped you would have. You took the time to answer a question about a tire but could not be bothered with mine?
kevm14 says:
06:21 PM, 09/27/10
"check the alignment, I’ll bet it’s not in spec."
Given how gross the tolerances are on stock alignments, I doubt it. Dan's probably right; if the wheel is centered, it's probably within spec. I used to go out of my way to find a shop who was willing to go the extra mile and dial in a good street alignment for my 93 Caprice (a little more negative camber, more caster and a touch of toe-in, with street friendly wear characteristics still). It was always noticeable.
slickersdrip says:
08:38 PM, 09/27/10
+1 bodyblue.
The editors have a great tendency to ignore pointed questions.
What was the real story with the Ford Edge, btw?
sodaguy says:
01:25 AM, 09/28/10
Dan,
Thanks for the explanation.
I guess it is a question of risk. Sure, the car is now pointing straight, but that does not mean the alignment is perfect. I personally believe that "in-spec" alignment is not enough, as the allowable ranges for toe (and other settings) are quite wide, and a reading that is merely "in spec" may not be ideal for tire wear or handling. Considering the vehicle's mileage and the irregular wear on the old tires, I think it is a wise investment to have the alignment checked and adjusted.
In addition, while it is true that toe is the only factory adjustable settings, it is possible to adjust the front camber with cam bolts and the rear toe and camber with shims. I never allow the lack of factory adjustments to force me to compromise for a less than perfect alignment-- I take advantage of available aftermarket alignment products whenever possible to obtain the best alignment.
Lastly, I have a follow-up question for you. You mention that if the steering wheel is perfectly centered, then the alignment is OK. From what I've been told, you can have a situation where excessive camber and toe-in will compensate for the result of no pull-- yet you still have a condition where the alignment is not correct. Similarly, how are you certain that the steering wheel is perfectly straight? Without having the car on the alignment rack, I am not sure that you can make such a statement as the steering wheel could be slightly off-center and it would not be noticeable unless you had another Prius with a perfectly centered wheel to compare against.
bodyblue says:
04:53 AM, 09/28/10
"+1 bodyblue.
The editors have a great tendency to ignore pointed questions.
What was the real story with the Ford Edge, btw?"
No kidding....Dan has been honest in the past but I did not expect an answer.....I think it would have been embarrassing to really say.
wyounger says:
05:28 AM, 09/28/10
Yep, I've had the front camber adjusted in my Prius by exchanging the camber bolts- at the dealer and apparently with factory parts. Among the Prius enthusiast boards you don't hear many reports of them coming from the factory in good alignment (I think my '07 was even slightly out of spec). After much fiddling and with the addition of some toe-in (though still within the allowable spec) the car doesn't wander as much as a typical Prius, and is bothered by crosswinds a little less.
Don't get me wrong, the steering in the '04-09 Prius belongs in a U-Haul truck, definitely the car's biggest weakness, but it can be helped somewhat by replacing the stock tires and at least getting the alignment optimized.
geokilla says:
07:47 AM, 09/28/10
Since when can you swap tires left and right? I know you can swap em front and back to take care of the uneven wear and stuff, but not left and right. In fact, doing so is dangerous last I checked.
wyounger says:
07:55 AM, 09/28/10
Left to right is fine and is part of normal tire rotation as long as the tire isn't a unidirectional design (with a big arrow on the side showing which way it's supposed to rotate), and you are highly unlikely to find a unidirectional tire on a low-performance car like a Prius.
actualsize says:
10:15 AM, 09/28/10
We're quickly venturing into territory where that longer article, nay, a textbook, is needed!
@sodaguy: One thing to remember is this: Our aim is to test these cars as a normal consumer might. We're intentionally not going for the perfect track alignment, as if we were slaloming the thing. This is a Prius, a commuter car, after all. We might think differently of a Z06 or GT-R, which will attract gearhead owners. Toyota publishes a spec for the car, and the alignment is within that spec according to a consumer-oriented shop or a dealer tech, it's testable. If the tires wear funny while within spec, then that's what they do. It is not in the best interest of consumer testing if we decide that, say, "+/- 45 minutes isn't a tight enough tolerance, let's do +/- 15 minutes instead".
Beyond that, yes, we will check the alignment to see where our Prius stands. This car has 85,000 miles on it. If it turns out it drifted out of spec, we'll adjust it. But at this point the front toe is balanced, left-to-right, that much is sure (see below). We'll find out if the actual total amount is within spec or not, but I suspect it still is.
As much as I'd like it to be otherwise, very few of our cars accumulate enough miles for many of these issues to become a regular part of our program. This particular and unusual high-mileage car has had an odd random history for reasons I can't delve into. In a way that produces an interesting result, because it may well be more applicable to typical consumer behavior. But I'd like to put every car through a 100,000-mile accelerated durability cycle and control every move they make in a specific and comparable pattern. Maybe someday, but for now that costs more money and manpower than I have in my budget.
Twist-beam axle shims or strut camber bolts are generally intended as crash-damage repair items. They shouldn't be necessary in normal practice unless the owner is intentionally going for a particular "limit" of the spec he or she deems desirable. I've been that autocrosser, that racer, the one that wanted the maximum negative camber allowed and a toe setting of my choosing, and I have used and installed twist beam axle shims and camber bolts in those efforts. But this is not the behavior of normal consumers who get "an alignment" when someone at a repair shop recommends it and talks them into it. In the spirit of consumer-based testing, I don't think we should second-guess manufacturer specs or tolerances in normal practice. If these pieces are needed to get inside the spec, great. If not, we'll *cough* steer clear.
As for wheel centering, I am confident that the wheel and the ESC sensor are properly centered at this time. Here's why.
Wheel-centering during an alignment is not rocket science. First you turn the wheel left and right to make sure there are more or less an equal number of turns to each lock, to make sure the wheel and steering shaft are on the correct spline. This will have been set properly at the factory, and as long as the wheel has never been off, this will remain the case forever. In normal circumstances, the steering wheel should never come off during an alignment.
Then you EYEBALL the wheel to a centered position, then install a spring clamp between the wheel and the front seat cushion so the wheel won't move easily from where you put it. Next you get under the car and twirl the left and right tie rod ends (after camber and caster are set) so the toe comes out equal and opposite on both sides. If the front pair of tires have balanced conicity (and the correct amount of intentional "ply steer"-- longer story, textbook, chapter 6), the wheel will remain in that spot while driving straight on a normally-cambered road (2 percent sloping down to the right). But the centering will only be as good as the tech's eyesight and judgment when he first applied the clamp. There's no rocket science here. The wheel is centered properly and the toe-in is "balanced" left-to-right if the wheel LOOKS like it is centered properly when you're driving straight with known good tires on a normally-cambered road. This accurately describes our Prius at this time.
Furthermore, our Prius' steering angle sensor is in the proper orientation not only because the ESC's response is now symmetrical, left to right, but also because the steering wheel and steering shaft have never be disconnected from each other or the steering rack itself. It could only get out of sync with the system if one of these had been previously removed and clocked to a different spline. This is extremely bad practice in any alignment and we know it didn't happen here.
Is there too much or too little total toe-in? I doubt it, but we'll check. And we'll look at the camber and caster, too. It is possible to loosen the two strut attachment bolts at the hub and play with the slop to make small changes without installing camber bolts. Of course the toe has to be reset whenever camber is touched.
@geokilla: swapping front tires left to right is an accepted way to diagnose/cure steering drift and pull. Many carmakers endorse it as a standard practice. It is generally not seen as dangerous. The old theory that overlapping tire plies take a "set" and should never be rotated the other way is an old wive's tale that may have applies a couple of decades ago, but not now. Remember, on front-drive cars, where these types of steering issues are most prominent, tires get "worked" in both directions daily, as they alternate between acceleration torque and braking torque. The only time you can't do this is in cases where the tread itself is directional. Such tires will be so marked with a proper rotation direction.
sodaguy says:
05:56 PM, 09/28/10
Dan,
Thanks for the great explanation. I look forward to seeing the results of the alignment. You are indeed, correct that there's no reason why the steering wheel should be off-center, especially since it sounds like the Prius has never had any suspension work performed.
However, I would like to add that there is a way of properly centering the steering wheel during an alignment. There should not be a need for eyeballing. I am not sure if the John Bean Company (JBC) racks have this feature, but with the Hunter WinAlign software, the computer will direct the tech to move the steering wheel until the sensors determine that the wheel is centered. Only at that point is the steering clamp supposed to be set.