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Tire Decision Quandary

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by sub3marathonman, Jun 5, 2010.

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  1. sub3marathonman

    sub3marathonman Active Member

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    I need to replace the original 185/65R15 Integrity tires, but there are many questions.

    1) What is the effect of going to the 195/60R15 tire? It seems to have the same rev/mile, so what is the difference?

    2) Which tire has a bigger contact patch with the road, a x/65R15 or a x/60R15 tire? Is the difference insignificant in real world performance?

    3) The 2010 Prius now has 195/65R15 tires. Will that size tire give a very slight improvement in mpg over the 185/65R15 tires (same manufacturer/tire line)? Does anybody know why Toyota switched sizes?

    4) Has anybody used the new Continental ProContact with EcoPlus Technology?

    5) Does anybody choose a tire based on the country of manufacture? Would you choose a different size just to get one made in the U.S.?

    6) Of the three sizes, 185/65R15, 195/60R15, or 195/65R15, is there any overriding reason to choose one size over the other?
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1) The 195/60 tire is wider, hence the tread patch in contact with the pavement will be slightly larger which results in better traction and increased rolling resistance.

    2) It depends upon the section width of the tire, i.e., 185, 195, etc. The larger number has a bigger contact patch.

    3) No, the 195/65 tire, all things being equal, should result in worsened mpg. Toyota probably went to a wider tire to improve handling and road feel.

    5) I don't really care where the tire is made; I care about the brand and model.

    6) My personal preference is to stay with the original equipment tire size because I don't have any problems with the car's handling (given a decent set of tires) and I prefer not to impair mpg.
  3. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    1) The 195/60 tire is wider, so will be less aerodynamic. The contact patch will be wider and shorter than 185/65, so it should turn better and brake in a straight line worse.

    2) Pounds per Square inch. The car weighs the same, so the contact patch will be the same number of square inches. Wider tires will have shorter patches.

    3) The 2010 weighs 150 more pounds and I bet it needed a larger load carrying tire.

    4) I have not.

    5) No, I chose Goodyear Viva Authority Fuel Max tires at Walmart. I was close to a Walmart when I ran over the nail.

    6) 185/65R15 was Toyota's best opinion, I do not know more than Toyota did.
  4. ursle

    ursle Gas miser

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    For best mileage 185 65 15", for best ride 195 60 15"

    Tirewrack or Discount tire (free shipping) will put em in your hands.
  5. vertex

    vertex Active Member

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    I just installed 205/60R15 Michelin Primacy tires. It has nearly the same circumference as the stock tire. I will take my first long trip with them tomorrow & report back on mileage.
  6. Boo

    Boo Boola Boola Member

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    Actually, they will not have the same revs per mile, although the difference is small.

    According to the Miata Tire Size Calculator, the average 185/65R15 tire has 824 revs/mile and the average 195/60R15 tire has 833 revs/mile (note however that actual revs/mile for different tires of the same size will vary).

    This means that if you put 195/60R15 tires on your car, the speedometer (and odometer) will over-read by 1%. So when the speedometer shows that you're going 60 mph with the new tires, you will actually be traveling at 59.4 mph (or the speedometer would have shown 59.4 mph with the original size tires).
    2 people like this.
  7. sub3marathonman

    sub3marathonman Active Member

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    Thank you ursle, that is exactly what I was wondering about. I guess the 0.4" additional height also causes a small increase in aerodynamic drag too. But I also remember that I liked the taller tire too because it added a bit more ground clearance for the Prius, which is extremely low and easily damaged because of it. (That's another story about another prius.)

    After a bit more research, I was also wondering what effect the tire weight had on mpg or anything else.

    And, the Continental ProContact with EcoPlus Technology tires present another not-all-things are equal choice between the sizes. First, the OE tires have 855 rev/mile, the Continental 185/65R15 has 848, the 195/60R15 has 858 (so almost exactly equal to OE), and the 195/65R15 has 831 rev/mile. Which as ursle pointed out, will change the gear ratio, and as others point out, will change the actual speed vs. indicated on the speedometer. So when the car thinks it is going 34 mph in EV mode, it would actually be going almost 35 mph, not that it really matters much though.

    Also, the 195s have 11/32" tread, as opposed to 10/32" tread for the 185, which to me indicates that they should last 12.5% longer ( (11/32 - 2/32) = 9/32 for 195s, (10/32 - 2/32) = 8/32 for 185s, 9 is 12.5% more than 8). And, the 195/65 tire is $2 less than the other two.

    So the choice is to sacrifice a bit of fuel economy for potentially longer tire life and a bit more ground clearance, and then too possibly better handling with the 60 series as opposed to better straight line braking with the 65 series.
  8. xpcman

    xpcman Active Member

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    Another Toyota knows best response. If the best tire is the 185/60 size then why did Toyota but 195/60's on the European models? Could it be the fact that they use "tyres" and be use the better "tires"? :rolleyes:
  9. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    1) Not knowing more than Toyota did, is not the same as Toyota knowing best. It is just a sign I know less.

    2) I did not find anyone (other than you) is discussing 185/60 tires/tyres.

    3) American highway speeds and European highway speeds may differ, making different tires/tyres better choices. I know the US Integrity tires are rated 1 MPH more than the Gen II US Prius is governed to go.
  10. redrockprius

    redrockprius redrockprius

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    I had a set of 185/65R15 Continental ProContact with EcoPlus Technology tires installed last week. I bought them from TireRack for $72 apiece. With shipping, the total came to $332. Mounting and balancing by one of TireRack's local associates, including tax and tire disposal fees, was about $75.

    I've used the tires driving around town for about 100 miles and for a 75-mile trip this morning that included winding, mountain roads at 55 to 60 mph, and about 25 miles at 75 mph on I-15. These tires are a great improvement in responsiveness over the original Goodyear Integrities. Based on indicated mpg on the MFD display, I can't see any significant change in mileage.

    I inflated them to 39/37, the same as I used on the original tires. It's hard to be sure, but I think the new tires are a little quieter on the road and give a shade more comfortable ride. The most noticeable change is in the handling.
  11. sub3marathonman

    sub3marathonman Active Member

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    I hope that this propaganda from Continental didn't influence your decision: "An emergency stop on a wet, slippery road can be a frightening experience. Tires are the only contact to the road during these adverse road conditions. When compared to a leading competitor, the ProContactTM with EcoPlus Technology stops up to 52 feet shorter 3." Then, with the little explanation for the 3: "Independent braking test compared 215/60 R16 95T Continental ProContactTM with EcoPlus Technology to P215/60R16 94T Michelin EnergyTM Saver A/S"

    I wrote to Continental to check into this claim, since 52 feet is gigantic. It would have been a major factor to choose the Continentals over the Michelins or pretty much any other tire. I received a reply from Russ Connor on 6/18/2010,
    "I have not forgotten you. Your request is the first that we have received for this particular test. As soon as I get their approval I will forward that information to you.
    Regards,
    Russ Conner
    Continental Tire the Americas, LLC.
    PLT Replacement Business Unit
    Customer Service
    704-583-8853 office
    704-804-1775 cell
    888-847-3329 fax
    russ.conner@conti-na.com "

    Now it is the end of September, I guess they forgot about me??? The first person to ask about it though. Hmmm. And some call me a skeptic?

    Oh, and I went with the Yokohama AVID ENVigor (H rated) from Tire Rack for $69 each with a $10/tire rebate, plus the $43 for shipping so it was about the same as when Tire Rack would offer free shipping.

    So far, I think these tires are fine. You can inflate them up to 51 psi, 850 rev/mile vs. 855 rev/mile for original Goodyear Integrity, so the speedometer is fine. They should have excellent low rolling resistance, but about the same time I changed the tires I got the Hymotion kit, so I can't isolate the tire contribution.
  12. redrockprius

    redrockprius redrockprius

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    No, that claim had no influence over my choice. In fact, I've never seen that particular claim. If I had, it would have meant nothing to me since the test conditions are not defined. Are they claiming a 52-foot advantage when stopping from 50, 60, 70 or ?? mph? Was the test track simply wet with water or with a friction-reducing agent? Was the test conducted with exactly the same car?

    I'm glad you're happy with your choice. I'm still quite satisfied with mine.
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  13. lew

    lew New Member

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    I have been using the Eco Plus tires on my '08 Prius standare, for almost 2k miles. They are superior tires to the OEM Goodyears (which i had to replace at 37k) in all ways. They are VERY quiet, smooth riding and show no signs of hydroplaning at all-even in heavy rains. They corner extremely well, with no leaning, and over bumps they hold the road so well, the traction control system engages much less frequently than with the OEM's. After about 800 miles the car regained the 2-3 mpg it lost with the new tires, and now, my city/hiway commute averages 50-53 in temperatures now ranging in the 50's-60's. Hiway driving with hills and AC, at 70mph, reduces the mph to 48. I was looking for Hydro Edge with Green x, but they were not available due to manufacturing problems, and I am really glad. These tires make the car feel better than new. I look forward to seeing how they do in the snow.
    2 people like this.
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