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Discussion Starter #1
After carefully investigating the tire specs/requirements for my Prius 2002, I went with the Goodyear Aquatred 3's -- now my Toyota dealer is trying to tell me I have to yank these off & "get the right tires for this heavy car." The Goodyear guys have reassured me that this tire will work very well for the Prius, and my review of the ratings, etc seem to confirm this. But I'm still a bit nervous 'cause of Toyota's warning. I'm starting to feel that I'm road kill being torn between two huge companies. Does anyone have experience with the Aquatred's on the Prius? Any and all advice would be appreciated.
 

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aquatred

Goodyear is wrong. The same thing happened to me. The 2004 Prius fixes this problem by going to a larger size. Currently, the only tire approved for the 2003 Prius or before is the Bridgestone Potenza(sic). There are weight issues that the other tires due not support, and neither will Toyota. Return the tires, and tell GoodYear to replace them with the tires that Toyota recommends. There are definite issues...
 

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I don't agree AT ALL with previous poster. Classic Priuses came in Europe on standard Michelin tires (Energy, probably a name for Europe only) and we had no problem with them. You don't need any special tires on the Prius, provided you meet the pressure and weight requirements. By the way, the Prius is not particularly heavy compared to its size, similar european cars are about the same weight. For some useful instructions on tires I recommend John's web site :

http://john1701a.com/

and particularly this section :

http://john1701a.com/prius/prius-tires.htm
 

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Discussion Starter #4
more on Aquatred 3s

Thanks for your input -- I actually used John's website when doing my research for the replacement tires for my Classic Prius and it seems that the Aquatred 3's meet all the basic requirements for the Prius ... they have the same "specs" as the recommended Goodyear Allegra (max load of 1019 lbs), the same speed & load rating of 81T. I can't find the max. PSI for the Aquatreds, but I'm still looking.
 

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Tires

All I know is when I contacted Toyota Corporation, they indicated that if the recommended tires were not used, not only could it invalidate my waranty, but any potential suit in case of an accident. They indicated that the tires MUST meet the size, load, and speed rating. I agree that the risk is almost non-existent with the Michellan(sic) tires, but when the manufacturer of the car tells me to only use the recommended tires, I will do what they said. Incidently, Goodyear had no problem replacing the aquatreads with what Toyota recommended at no cost to me. Why do you think Toyota created a larger tire size for the 2004? It was to meet the size, load and speed rating.

Good luck to all...
 

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Tires

Incidently, read John's disclaimer:

"The ideas, suggestions, and opinions offered on this webpage have not been endorsed by the manufacturer of those specific components or Toyota Motor Corporation. Any harm or damage that may result from the application of or the following of any ideas, suggestions, or opinions contained in this document is the sole responsibility of the individual that applied or followed said ideas, suggestions or opinions. The authors of this document hereby declare that they cannot and will not be held liable, in any fashion, for the content or the use of this document. "
 

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They indicated that the tires MUST meet the size, load, and speed rating.
Of course they must, like on any car. But it's the only requirement, the Prius needs nothing more specific than any other car.
Why do you think Toyota created a larger tire size for the 2004? It was to meet the size, load and speed rating.
Wrong. All these requirements were already met on the previous version. Now the tire choice is always a balance between fuel economy, road-holding, price etc. A way to decrease rolling resistance (and therefore improve fuel economy) is to use small tires at high pressure. The new Prius beeing designed as a more "sporty" car than the classic, Toyota decided logically to increase the tire size. They even went further in Europe and Japan where the Prius has 195/55 R 16 tires.

Now for John's disclaimer, that seems just common sense in a country such as the USA... :wink:
 

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On my '02, I run Bridgestone B420s, which are not XL, at 44 psi. This is to obtain their maximum load capacity (1,019 lb.) as per specs on the sidewall. Total load capacity is 1,019 lb. X 4 = 4,076 lb. on a vehicle with a GVWR (car plus load) of 3,615 lb. This seems plenty adequate to me.

The Bridgestone Potenza XL has a 50 psi inflation maximum. Toyota's inflation recommendation is 37/35 front/rear. At this inflation the Potenzas, which are only 160 treadwear-rated to begin with, wear out quickly. Plus, the tires are underinflated by 13-15 lb. Some of us Explorer owners recall what happened when Ford recommended 26 psi for a 35 psi tire.

Since most of us don't know at just what point an underinflated tire becomes a dangerous tire, I prefer to run my tires on the "hard" side as per the tire sidewall, regardless of the car manufacturer's recommended pressure (where ride comfort may be the principal factor, as it apparently was in the Explorer-Firestone debacle).
 

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Discussion Starter #10
So. it seems that the Aquatred's should work on the Prius -- they seem to match the specs of the Bridgestone tire mentioned in Henry's post. I agree on the inflation to 42-44 PSI -- I like a harder ride myself. I've checked all my warranty info on the '02 Prius and it doesn't seem that using a different type of tire affects any of the other vehicular warranties, so I think I'm going to stick with the Aquatreds, monitoring them closely (the Goodyear dealer said they'd be interested in how the tire does, so will help me monitor the wear on these). I'll try to keep the results posted in this forum. Thanks for all your input and discussion -- it has been very helpful (thank goodness for the Internet!)
 

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Henry said:
On my '02, I run Bridgestone B420s, which are not XL, at 44 psi. This is to obtain their maximum load capacity (1,019 lb.) as per specs on the sidewall. Total load capacity is 1,019 lb. X 4 = 4,076 lb. on a vehicle with a GVWR (car plus load) of 3,615 lb. This seems plenty adequate to me.

The Bridgestone Potenza XL has a 50 psi inflation maximum. Toyota's inflation recommendation is 37/35 front/rear. At this inflation the Potenzas, which are only 160 treadwear-rated to begin with, wear out quickly. Plus, the tires are underinflated by 13-15 lb. Some of us Explorer owners recall what happened when Ford recommended 26 psi for a 35 psi tire.

Since most of us don't know at just what point an underinflated tire becomes a dangerous tire, I prefer to run my tires on the "hard" side as per the tire sidewall, regardless of the car manufacturer's recommended pressure (where ride comfort may be the principal factor, as it apparently was in the Explorer-Firestone debacle).
Actually, both the classic Prius and
the 2004 Prius have the same tire
pressures listed on the door jamb:
35 psi front, 33 psi rear.
 

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I stand corrected---too lazy to hop out to the driveway and check, and relied on faulty memory. I ran my Potenzas at 42/40 and was actually getting good wear from them until one got punctured. But Toyota's 35/33 is even worse than my erroneous numbers!
 

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Yokohama Avid Touring

These tires have worked out great for me on my 2002 Prius. Yokohama Avid Touring. They are not rated extra load. Filling them up to 42 PSI front and 40 PSI rear has compensated for that. No drop in MPG even though they are not rated LRR.
 

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I Use AquatredIII's

I has 185-65-14 Aquatred III's on my 2002 Prius and they work just fine. Because they are a size larger that the originals, the load rating is 85T. This is much better than the lousy OEM Bridgestones. These tires have a max inflation pressure of 44 psi, and I run them at 40/38 front/rear. In the winter I use 185-65-14 Yokahama Guardex 720 snow tires on steel rims. After running the larger Aquatred's on my '02 there is no way I would go back to the OEM Bridgestones.
 

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Replacement Tires

I recently replaced the OEM Bridgestones on my 2002 Prius with Michelin HydroEdge tires (185/65x14, 44/30 PSI). They are a little noisier than the Bridgestones at low speeds, but very quiet as speed picks up. Performance is a great improvement over the original tires, and the Prius now handles like a normal car (not fidgety in the front end at high speeds).

Despite what I heard about poor traction in ice and snow, a recent trip to Utah disproved this information. The tires provide great driving confidence on dry, wet and snowy roads, and the only drawback is the increased rolling resistance. I was surprised that the extra drag is immediately noticeable when coasting to a stop. The speedometer reading drops twice as fast as with the Bridgestones.

After 5,000 miles, I have confirmed that there is about a 4 mpg decrease in mileage, mainly noticeable in city driving. Highway mileage seems only slightly less, but city mileage has dropped from 47-48 mpg to 43-44 -- an anticipated loss, but still disappointing. The sacrifice in mileage is worth the improvement in tire performance and safety, but I wish that Michelin made a low rolling resistance tire for the Prius.

During the last maintence visit, the dealer added a note on the invoice "wrong sized tires". The service rep didn't say anything to me, so I guess that this is OK. Has anyone had any comments from the dealer on using tires other than the Bridgestones?
 

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A few (everything is relative) words on tires and pressures.

Low rolling resistance tires are a specialty item. As is the case in most engineering, design is a series of tradeoffs. Take for example, tire wear. Many of the factors that contribute to long wear in tires do not support some of the other desirable attributes such as traction, wet braking, etc. Similarly, factors contributing to better low rolling resistance performance are at odds with longivity, while retaining traction etc. Some compromise is in order to prevent losing too much ground in any important area of tire performance.

All the manufacturers work with essentially the same materials and laws of nature. It isn't something that you can "fix" at reasonable prices, if at all. It is unrealistic to expect any manufacturer to be able to deliver stellar performance in all rating attribute categories even if their name is Michelin.

Tire pressure: Tires are not neccessarily better because their max safe pressure is higher. Max load rating is important and should always exceed the greatest load ever carried. B U T, that said, it is important to note that the correct tire pressure is not usually the max pressure written on the sidewall. Brief physics lecture follows... (Frenchie, keep me honest.)

To a close approximation, the inflation pressure of a tire multiplied times the area in contact with the ground (footprint) is equal to the weight on that tire. Added up for all 4 tires and you have the loaded weight of the car. Too much pressure and the tire only contacts the road in a small patch at the center of the tread, wearing out the in the center while the edges of the tire remain essentially unused. With pressure too low, the tire tread buckles and most of the weight is carried on the edges of the tire with the center tucking up and away from the road.

Most of us are familiar with the gist of this dissertation and should be able to track the following logic. Somewhere in between way too much and way too little is a zone of pretty good. This is where even tire wear wil be achieved and give longer mileage AND with more tire in contact with the road you will get better traction for steering, accelerating, and braking.

Inflating a tire with a terrific load carrying ability to its maximum pressure when installed on a car that is much lighter than the maximum load will result in serious overinflation. This overinflation is not a hazzard to the tire but to safety and performance. It doesn't overstress the tire but it reduces the contact area and will result in lowered life and poorer traction.

Do not interpret this to mean you should not buy high load rated tires. I prefer tires with a good safety margin of load carrying ability as it implies stronger construction. I DO NOT arbitrarily inflate them to the manufacturer's max rating. It is a MAX rating not a recommendation for any specific application. That MAX pressure is only needed to carry the indicated MAX load. Since you are carrying less you need less pressure for proper tire shape.

Recommendations on the car's door jam sticker or in the manual often give increased pressures for sustained high speed driving. This is because one of the greatest tire killers is heat build up from high speed driving (assuming tires are not run underinflated). The extra pressure is a compromise that reduces tire flex (source of the heating) while operating nearer the upper end of the envelope of proper shape (pretty good zone, mentioned above). I suggest that you will get lower rolling resistance at the high speed pressure and that with only a minor reduction in tread life if you use the high speed pressure for everyday driving. For you "Princess and the Pea" types, you might note a slightly harsher ride. I would not recommend exceeding that high speed pressure for everyday driving.

Perhaps someone well connected with Toyota engineering info will chime in and tell us how far they are pushing the envelope with tire pressure to further reduce rolling friction and increase gas mileage.

As others have noted, the stock tires don't give really long service. That isn't a surprise, tire longivity wasn't the attirbute they were trying to maximize. A good question for those who may have kept really good detailed expense data on their Prii would be: Did buyinig tires that gave longer service (but lower MPG) end up saving any money?

You save on tires at the expense of buying more gasoline but did you save more $ on tire mileage than the increased $ for Gasoline? If yes, and environmental considerations don't sway the decision, then better to buy long life tires and spend more on gas. Or perhaps the ECONOMY of this issue will run the other way and you'll be better off saving the gas and buying tires more often. Any accountant/budget analyst types out there want to share the findings of their detailed records keepiing?????

Pat
 

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Replacement Tires

Sorry, I didn't see the latest response (which was on the next page) until after I posted my last message.

I agree with your explanation, though I arrived at the same conclusion by observing the contact patch on the tires. I set inflation pressures to provide the most even contact patch. (You can see the portion of the tread that contacts the road after driving through fine dust.)

44 psi on the Michelin HydroEdges provides full contact across the tread on the front tires, with minimal sidewall scrubbing. Similar pressure in the rear tires shows that only the center of the tread contacts the road. I gradually deflated the rear tires until the contact patch was the same as the front tires, which ended up around 30 psi.

For trips, I check the contact patch on the rear tires with the car fully loaded and pump up the back tires accordingly. Usually, 2-4 psi additional is sufficient.

The rolling resistance is a function of rubber compound and ply and belt composition and bias angles (and probably a lot of other factors that only tire manufacturers know). For long wearing tires, the rubber is usually fairly hard to reduce scrubbing. This usually reduces grip, which is compensated for by tread design. The tread is a function of the desirable traction and handling characteristices, e.g. higher void to rubber ratio for snow and mud, and closer to slicks for summer high speed highway driving.

The HydroEdges are long wearing tires, with a relatively hard rubber compound and a tread design optimized for rain. So, I think the higher rolling resistance is probably a function of the belts and plies. They have an Arimid belt in addition to the steel belts, but Michelin must have made some compromises in the sidewall plies to soften the ride, which might have increased rolling resistance.

Don't get me wrong, these tires perform well and are very comfortable riding -- and are obviously not high performance tires. They just don't roll as well as the Bridgestones. Also, they are really heavy. I think the Bridgestones weighed about 15 pounds and the HydroEdges are about 21 pounds each. (I may not have these numbers quite right, as they are from memory, but you get the idea.)

Thanks for your insight -- Just wish these got better mpg!
 

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Phoenoix, Hey, thanks for the tip about the fine dust thing. The first thing that came to mind when you said you "looked" at your contact patch was driving over a STRONG but transparent surface and viewing from below like I've seen on TV.

Pickups are an even greater tire inflation challenge as they change weight, especially in the rear, by a larger percentage. I changed out the stock wheels and tires on my 1 ton from 16 inch rims to 19.5 inch rims and run Michelin 245R85 19.5 rated for a max inflation of 110 lbs. Every yahoo who checks the pressure wants to inflate the tires to 110psi, even the duals in the rear. The stock tires ran something like 50 in the rear and 65 in front (Cumins diesel is a lot of cast iron). Larger tires with the same load don't need twice the pressure!

These tires may rot off before I can wear them out even though I go off road and they are mud and snow tread. I have about 65,000 miles on them and they are about 1/4 to 1/3 used up. The "highway" tread version lasts the high mileage drivers about 200,000 miles. The sidewalls proclaim them to be "Regrovable" but I don't know if that is for me.

How does this relate to a Prius? Prii have tires, that were selected, undoubtedly, under pressure of compromise. Lowest rolling resistance without compromising safety through loss of traction, heat resistane, and so forth. It is difficult or impossible to maximize all desirable attributes simultaneously, something has to "give." In the case of stock tires on the Prius, it seems wear rating may have been sacrificed in favor or low rolling resistance.

"My" dealer called yesterday to tell me that "My" color Prius just arrived if I want to come drive it or whatever. I declined as it is package #6 and we want #9. We are #1 on the list and get first crack as Prii arrive but could wait more months to get a #9. Once Prii equipped, I'll probably look into tires for it a lot more serioulsy.

I wonder how practical it is to only change out the drive tires to mud and snow tread and leave the rear, as is? I wold probably opt for getting another pair (quad? if I must) of wheels to mount up the snow tires. I am ot so concerned with highways and city streets as I am my own driveway.

We are building a new house about 1/4 mile down a gravel road (section line) off a state highway. Then the gravel drive is nearly 1000 ft long with a bit of hill in it, 2 rt angle turns, and a 135 degree turn into the garage. The incipient Prius delivery gives me pause to rethink the driveway geometry a bit and perhaps reduce the change of grade in the 135 degree turn. When 4x4 was the only way to fly (prior to becoming a prius convert) it was not even an issue, now I am concerned that the Prius might not make it out our driveway when there is enough snow cover to get the tires off the gravel or there is an ice coating. I'd hate to have to take the pickup (has 12,000 lb winch on front bumper) out to winch the Prius up to where it could make it on its own.

Pat
 

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Driving in the Snow

Sorry, I am not much help with driving in the snow. We went through a little in a recent trip to Utah, but I don't think a 2-3 inch dusting is like an Oklahoma winter dirt road.

If the Prius is like other front-wheel-drive cars, it will probably do great with just the front tires switched to snow tires. That would be fine for Arizona and California residents who have to drive to the snow on weekends to experience it. However, if you LIVE in the snow, you will probably benefit from switching all four wheels to snow tires. The extra safety margin in stopping would probably justify the extra expense. Also, if you are still running the OEM Bridgestones, even snow tires will outlast the Bridgestones on treadwear, and you can save the OEM rubber for the summer.

Let us know when you get your 2004. I am going to wait another year or two, then replace our 1998 Camry with a new Prius. We're going to keep the classic Prius, though. It's a great little car!
 
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