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How to know which tires are most efficient?

Discussion in 'Prime Fuel Economy & EV Range' started by rbwilli, Oct 23, 2022.

  1. rbwilli

    rbwilli New Member

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    As I mentioned in my previous thread, my wife saw a significant drop in EV range in her 2018 Prius Prime a few months ago. (Real-world range, not just predicted; she used to be able to make it all the way home with a little range to spare, now she runs out with some miles to go. I did a test today since the weather was perfect—it was 67 ºF—and even without any heat/AC/fan use at all, the reduced range persists.) The drop coincided with changing from a set of fairly worn-out Toyo Nanoenergy A29 tires to a new set of Primewell all-seasons.

    I have no idea how to predict the impact of a given set of tires on fuel efficiency. Is there such a thing as an efficiency rating for a set of tires? Or the degree to which they have low rolling resistance? How can we know in advance how efficient a particular type of tire will be?
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Consumer Reports does list tires and the relative efficiency within the group (their usual colour-coded up and down arrows). Otherwise, going with one of the OEM models is usually a safe choice (Yokohama Avid, Bridgestone Ecopia EP422 etc)
     
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  3. bisco

    bisco cookie crumbler

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    unfortunately, no efficiency standards, so no ratings. not familiar with primewell, but they could certainly be a large part of the problem.
     
  4. CR94

    CR94 Senior Member

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    Keep in mind that tires have higher rolling resistance when new than when worn. That effect was at least part of the drop you noticed.
     
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  5. rbwilli

    rbwilli New Member

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    Interesting, I figured they would weigh a little more, but I wasn't aware of the explicitly higher rolling resistance with a new tire. Makes sense. Thanks!
     
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  6. Mendel Leisk

    Mendel Leisk Luddite

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    New tires also have larger OD, meaning the car think's you've travelled not as far, as when those tires are worn down, smaller OD, more rev's per mile, but the car then think you've travelled further. Fairly trivial, but a factor.

    One tire I got (on a privious car) that really hit the ground running as they say, was Bridgestone Ecopia EP20. They were OEM on some Prius, only came in 195/65R15 IIRC. And I believe they've been discontinued. When those were put on, replacing worn Bridgestone Insignia SE200_02 (no mpg slouch either), the mpg never skipped a beat.

    FWIW, mpg aside, they were very noisy when worn, and a menace in any amount of snow.

    Hmm: Canadian Tire claims to have the EP20.
     
  7. rbwilli

    rbwilli New Member

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    That's an interesting thought about the diameter and how far the car thinks it's gone. In this case it's not a factor, though (or only a minimal one), because we know she can't go as far on the same physical route. (That is, she can't make it to work and back on EV mode alone.) Encouraging that the new Ecopia EP20s didn't ding your efficiency! I'll have to keep an eye out for them—or whatever replaced them, if there's a newer model—when it comes time to switch again!
     
  8. Mendel Leisk

    Mendel Leisk Luddite

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    Probably Bridgestone Ecopia EP422 Plus. I suspect they gave up a slight edge in rolling resistance, but they're an OEM tire used by Toyota on the Prius, so...

    One thing, the EP422 from the factory are a Made-In-Japan version. There's also two other versions, more readily available in the North America: one manufactured in the States, the other in Mexico. All three have physically different tread patterns, and various specs are different. And they all have the same name. One of them, the US itteration IIRC, has very wide longitudinal gaps, one less row of tread, in 195/65R15 at least. There was one member here reported a tire shop tried to sell him 2 US and 2 Mex, when he was replacing all tires.
     
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  9. MikeDee

    MikeDee Senior Member

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    If you buy the Bridgestone EP422 Plus from the dealer, will you get the Japanese version?
     
  10. Mendel Leisk

    Mendel Leisk Luddite

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    I don’t think so. Ask? Around here I think dealerships mostly sell just snow tires.
     
  11. FuelMiser

    FuelMiser Senior Member

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    Try searching "fuel efficient tires for prius" in your favorite Search Engine
     
  12. Mendel Leisk

    Mendel Leisk Luddite

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    With the dearth of accurate LRR data, there could be a buisness model for a website, something like "Bob is the Tire Guy"? Develop a database of opinion, for various factors, LRR included? Maybe it already exists?
     
  13. MikeDee

    MikeDee Senior Member

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    Consumer Reports tests tire on a dynamometer for rolling resistance.
     
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  14. pasta4breakfast

    pasta4breakfast Junior Member

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    I experienced the same thing this year with my 2020 prius prime. I was getting arount 6-6.1 miles/KWh until I got a nail in my tire after 42,000 miles. I replaced all 4 of my factory installed Dunlop Ensave tires with Michelin X-Tour tires on June 6th 2022. The efficency dropped about 10% to 5.4-5.5 miles/KWh and hasn't appeared to to recover after driving 10,000 miles. You can see a table of my efficency in 2021 and 2022.

    Effeciency (miles/KWh)
    Month ---------- 2021 --- 2022
    January -------- 5.3 ----- 5.7
    February ------- 5.8 ----- 5.9
    March ----------- 5.6 ----- 6
    April ------------- 5.8 ----- 6
    May-------------- 5.8 ---- 6.1
    June-------------- 5.8 ---- 5.5
    July -------------- 5.9 ---- 5.4
    August ---------- 6 ----- 5.5
    September ---- 6.2 ---- 5.5
    October -------- 6.1 --- 5.5
    November ----- 6.2 ---- 5.4
    December ----- 5.6 ---- 5.2
     
    #14 pasta4breakfast, Jan 6, 2023
    Last edited: Jan 6, 2023
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  15. randerson9248

    randerson9248 Junior Member

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    I have a 2000 Honda Insight hybrid. The original tires were a Bridgestone Potenza. I went thru several sets of those tires, they had terrible tread life, but good low rolling resistance. Those tires are getting hard to come by, so the last set I bought were a LRR Dunlop. MPG dropped dramatically, by about 10mpg. The car can no longer maintain highway speed in 5th gear with the AC on. By highway speed. I mean 60mph. That's how bad the Dunlops are. I wish there were published numbers on actual rolling resistance.
     
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  16. pasta4breakfast

    pasta4breakfast Junior Member

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    I just wanted update everyone, since I now think my original post was misleading. Now that I have put 24,000 miles on the new X-tour tires, I believe they may only be 2-3% less efficient than the factory installed Dunlop Enasave tires. Also, I could have sworn I ran over peace of wood on the freeway with several nails poking out like a porkypine and didn't observe any evidence of a puncture on my X-tour tires. On June 2021, I had about 23,000 miles on the original tires and was getting 5.8 miles/KWh. June of this year, I had about 20,000 miles on the replacement Michelin X-Tour tires and got 5.7 miles/KWh. That is only a 1.7% reduction in efficiency. I think I am driving a little slower and using a little less A/C this year. Even if this adds another 1-2% efficiency, That is still only a 3% drop with the X-tour tires. Initiallly I thought the X-tour tires were 10% less efficienct because I noticed a 9-12% emediate drop in efficiency after replacing the tires and didn't notice any consistent improvement in the following 10,000 miles on the new tires. It appears that tires very gradually improve in efficiency as they wear. There is no early break-in period where they rapidly reduce rolling resistance and then stablize. When you replace the tires you notice a significant drop in efficiency, especially in a care as efficient as a prius prime. It then takes a long time for that efficiency to return. I guess you can only compare efficiency between tires with the same number of miles on them. Hopefully, I can get +/- 6 miles/KWh again a year from now, when I will have as much miles on them as the original tires. See the updated table below

    Effeciency (miles/KWh) - Tires replaced June 6th, 2022
    Month......... 2022.. 2022.. 2023
    January------ 5.3---- 5.7 ---- 5.2
    February---- 5.8---- 5.9 ---- 5.3
    March-------- 5.6---- 6.0 ---- 5.3
    April---------- 5.8---- 6.0 ---- 5.7
    May---------- 5.8---- 6.1 ---- 5.7
    June---------- 5.8---- 5.5 ---- 5.7
    July----------- 5.9---- 5.4 ---- 5.8
    August------ 6.0---- 5.5 ---- 5.9
    September- 6.2---- 5.5
    October----- 6.1---- 5.5
    November-- 6.2---- 5.4
    December-- 5.6 --- 5.2
     
    #16 pasta4breakfast, Sep 1, 2023
    Last edited: Sep 1, 2023
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  17. rbwilli

    rbwilli New Member

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    pasta4breakfast! Thanks for keeping us updated on your situation. To my eye, it looks like you have three months where the energy efficiency was only slightly reduced compared to your previous set of tires (June, July, and August 2023), and you have…12 months? (the 12 months preceding June 2023?)…in which efficiency was markedly lower. So it may be too early to say whether the tires are only slightly less efficient, depending on this summer’s weather, your A/C use, how inflated the tires are, your driving style, etc.

    My wife’s efficiency has never returned after the switch, in fact it seems as bad as ever, which surprises me somewhat. She recently destroyed a tire, so I had them replace it with one of the original Nanoenergy A29s. One down, three to go!

    An interesting counterexample to what we did would be to watch the efficiency after replacing a worn set of tires *with the same model of tire.* Presumably, the efficiency would eventually fully recover. I wonder whether it would take a month, a year, or many years!
     
  18. pasta4breakfast

    pasta4breakfast Junior Member

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    I guess only time will tell. Your situation may be different, as I am unfamiliar with Primewell tires. Either it is bad luck or not a good sign that one of them got destroyed so soon. Does your wife put a lot of miles on this car. If she is only putting 10,000 miles a year on it, it may take almost 2 years to notice an improvement in efficiency if my experience is applicable. There is a typo on the first column of my table. It should be 2021, not 2022. Actually, I only got a 0.1 mile/KWh drop in efficiency for the last 5 months in 2023 compared to 2021 when the original tires had a similar amount of miles on them or more. I don't think it is fair to compare them to the previous year because the old tires would have had over double the amount of miles on them. In April 2021 the original tires had about 19,000 miles and I got 5.8 miles/KWh. In April of 2023, the new X-tour tires had 17,000 miles on them and they got 5.7 miles/KWh. I wish I kept track of the efficiency the first year I had the car. It would be informative to compare the first year I had the car to the first year of the new tires.