When round and black becomes lean and green

Discussion in 'Articles' started by xcel, Sep 11, 2009.

  1. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    [​IMG] The best_FE and Traction tire data ever created is now in your hands.

    [fimg=left]http://www.cleanmpg.com/photos/data/501/2008_Toyota_Prius2.jpg[/fimg]John Rastetter - Tire Rack - Sept. 11, 2009

    Multiple 2009 Toyota Prius-II’s put to the test to give you a choice.

    It takes energy to drive a vehicle down the road and part of that energy is converted into power to overcome the vehicle's aerodynamic drag, driveline friction and the tires' rolling resistance. While drivers can't do much about drag and friction once they've bought a vehicle, the question is can eco-friendly, low rolling resistance tires make a difference in fuel economy, driving costs and the environment? The answer is yes.

    Tires are made of about 80% rubber by weight and rubber is a viscoelastic material that naturally converts some energy into heat every time it's compressed or stretched. Tires resist rolling primarily because their sidewalls and treads continuously bend and stretch as they transition from their loaded (where the weight of the vehicle causes the sidewalls to bulge as the tread footprint flattens against the road) to unloaded profiles.

    Tire rolling resistance and its influence on vehicle fuel efficiency has not been widely rated or reported in the past, so little comparative information is available. However, since every gallon of gasoline saved reduces personal fuel costs and America's dependence on oil, as well as releases 20 fewer pounds of CO2 gas into the atmosphere from the tailpipe, tire rolling resistance information and its contribution to vehicle fuel economy is scheduled to become more readily available in the next couple of years thanks to California and Federal legislation.

    While tire rolling resistance often has been reduced in the past by sacrificing wet traction and treadwear, the newest high-tech, fuel-efficient tires proclaim to have achieved low rolling resistance without compromising traction and wear through the introduction of new tread compounds and weight optimizing manufacturing processes.

    With multiple manufacturers introducing low rolling resistance tires in 2009, the Tire Rack team felt it was time to evaluate the influence these new tires have on vehicle fuel efficiency, as well as confirm if the manufacturers had to sacrifice traction to achieve it. We included a fuel economy evaluation as part of our Real World Road Ride and measured dry and wet traction limits while braking and cornering.

    Tires tested
    Vehicle(s) tested - 2009 Toyota Prius’

    The Cars

    [fimg=right]http://www.cleanmpg.com/photos/data/2/2009_Toyota_Prius-II_1.jpg[/fimg]Unfortunately not all of the latest low rolling resistance tires are available in a size appropriate for our normal test cars, so we arranged to get a small fleet of the popular 2009 model year 2nd generation Toyota Prius hybrids for this test. All of the cars had equivalent miles registering on their odometers and were treated to identical conditions while they were in our care to assure accurate results.

    In preparation for our test, the test tires were mounted on Prius Original Equipment 15x6.0" alloy wheels and all of the cars received four-wheel alignments using the vehicle's preferred settings to prevent any unwanted tire scrub from influencing vehicle fuel economy.

    The Tires

    Our test began with the premise that the Goodyear Integrity tire used as Original Equipment (O.E.) on the 2004-2009 Prius would establish the baseline for this test, since it's a tire almost all 2nd generation Prius owners have experienced. We then compared it to today's choices, with one end of the range being eco-friendly aftermarket tires now available for hybrid and fuel-efficient compact cars owners. The other end of our range was represented by the Goodyear Assurance ComforTred. Introduced in 2004 before aftermarket fuel-efficient tires became popular, the Assurance ComforTred features a 20% thicker rubber cushion between its tread and belts than standard passenger tires to prioritize ride comfort and long wear over fuel efficiency.

    The 185/65R15-sized OEM and aftermarket tires were new, full tread depth tires that covered several tire performance categories.

    Column1Column2
    Tire LinePerformance Category
    Bridgestone Ecopia EP100Grand Touring Summer
    Goodyear Assurance ComforTredPassenger All-Season
    Goodyear Assurance Fuel MaxPassenger All-Season
    Goodyear Integrity Passenger All-Season, O.E.M.
    Michelin Energy Saver A/SPassenger All-Season
    Michelin HydroEdge with Green XPassenger All-Season
    Yokohama dB Super E-SpecGrand Touring Summer

    All-season tires are appropriate year-round choices for drivers living in geographic areas that might encounter moderate snow. Summer tires are appropriate choices for drivers living in sunbelt areas that experience only dry and wet roads, or for drivers living in snowbelt states that switch to winter / snow tires with the annual change of seasons.

    Tire Pressures

    We could have begun with higher than normal cold tire inflation pressures to improve fuel economy, but we didn't want to deviate from the vehicle manufacturer's placard recommendation for this test. Additionally our experience is that while low tire pressures increase tire rolling resistance, higher than recommended tire pressures don't reduce tire rolling resistance to the same degree.

    Cold tire pressures were set to the vehicle manufacturer's recommendation of 35 psi front and 33 psi rear early in the morning after the cars were parked outside overnight. We also checked tire pressures late in the afternoon as our team completed their driving and when road and air temperatures had reached their highs. As expected, hot tire pressures had risen with use and measured an appropriate 39 psi front and 37 psi rear, ±0.5 psi.

    The Real World Road Ride Conditions

    [fimg=right]http://www.cleanmpg.com/photos/data/2/2009_Toyota_Prius-II_2.jpg[/fimg]Our Real World Road Ride consisted of over 550 miles on each tire during multiple laps of a 6.6-mile loop of public roads that combined 65 mph expressway, 55 mph state highway and 40 mph county roads along with two stop signs and one traffic light every lap. Our drivers encountered moderate vehicle traffic and averaged about 40 mph throughout the day.

    In order to keep our fuel economy results as accurate as possible, we only conducted our Real World Road Rides in dry conditions. Since tire treads encounter more resistance driving through water than they do through air, rain soaked roads would have introduced a water depth variable that we couldn't have accurately accounted for.

    Since we wanted to compare results that typical drivers would experience, our drivers were instructed to maintain the flow of traffic by running at the posted speed limits and sustain the vehicle's speed using cruise control whenever possible. They also came to a complete stop at the stop signs and waited at the traffic light as necessary.

    Fuel Economy Results

    Rather than using the Prius' on-board trip computer that assumes the dimensions of all tires are identical when it computes fuel economy, we used Race Technology DL1 GPS data loggers to record driving speeds and absolute distances, along with Linear-Logic ScanGauge IIs to monitor how much fuel was consumed. We alternated which car led our convoy every session and rotated the tires from car to car every half day to assure the accuracy of our data and neutralize vehicle variables.

    The U.S. EPA rates the 2009 Prius with a combined city/highway fuel economy of 46 mpg using regular grade gasoline. The Prius hybrids used for this test returned an average of about 52 mpg with their air conditioners on. We attribute our higher than normal mpg average primarily to vehicle preparation (accurate alignments and tire pressure maintenance), driving conditions (consolidating trips and not speeding) along with a route that only exposed our team to moderate traffic and a limited number of stops.

    [fimg=left]http://www.cleanmpg.com/photos/data/2/2009_Toyota_Prius-II_3.jpg[/fimg]
    Fuel Economy recorded for each tire and its relative position compared to the OEM tire's average is shown below.

    Column1Column2Column3
    Tire LineTest MPG* (US)% over/under vs. OEM
    Michelin Energy Saver A/S53.8 mpg+4.74%
    Bridgestone Ecopia EP10053.5 mpg+4.12%
    Yokohama dB Super E-Spec52.8 mpg+2.81%
    Goodyear Assurance Fuel Max51.6 mpg+0.37%
    Goodyear Integrity (OEM)51.6 mpg---
    Michelin HydroEdge with Green X51.1 mpg-0.59%
    Goodyear Assurance ComforTred50.0 mpg-2.64%

    *Calculated based on GPS distances and ScanGage II recorded consumption
    (offset 6% for Prius Summer E10 regular grade fuel).​

    In the case of the Prius, one of the most fuel-efficient cars in America, the difference between our lowest and highest recorded miles per gallon would result in an annual difference of about 21 gallons of regular gasoline consumed at a cost of about $52.50 (at $2.50/gallon) for drivers traveling 15,000 miles a year. Multiply this difference by several years of driving and the value of using low rolling resistance tires steadily increases. Additionally, you can also apply similar percentages of improvement in fuel economy to other vehicles. The fuel saving dollar value of eco-friendly, low rolling resistance tires essentially doubles or quadruples when applied to typical cars that deliver 25-30 mpg or light trucks and utility vehicles delivering 12-15 mpg.

    What We Learned on the Road

    Our expressway, state highway and county roads provide a variety of road conditions that include smooth and coarse concrete, as well as new and patched asphalt. This route allows our team to experience noise comfort, ride quality and everyday handling, just as most drivers do during their drive to school or work.

    The nature of the 2nd generation Prius and its design characteristics allow a fair amount of exterior noise into the cabin, which proved to mask some of the tire noise, especially at higher speeds. Our team also found the suspension tuning of the Prius to be somewhat soft, resulting in extra suspension movement over the rough sections of our road ride route. In the end we found that tire choice can have a noticeable influence on how the car drives and feels.

    As its name promises, the Goodyear Assurance ComforTred provided the most comfortable ride of the group. This tire did a good job controlling jounce and jiggle as the Prius chassis encountered patched concrete expansion joints. The Bridgestone Ecopia EP100 followed, also doing a good job minimizing how much of the road's bumps made their way to the driver. Right behind was the Michelin Energy Saver A/S, which also displayed good ride characteristics, allowing just slightly more of the road's texture to find its way into the cabin. Not far behind was the other Michelin tire in the test, the HydroEdge with Green X. Behind this front group were the Goodyear Assurance Fuel Max and the Yokohama dB Super E-spec tires which felt harsher over nearly all road surfaces, and the Goodyear Integrity, which had a relatively soft ride but felt harsh when it encountered the bigger bumps and patched sections of roadway.

    For overall noise comfort, the ComforTred again led the group with the least amount of tread noise relative to the other tires in the evaluation. Following close behind were the Ecopia EP100, Energy Saver A/S and HydroEdge with Green X. All three were rated closely, with similar overall noise levels and only small differences in any distinct pitches that could be heard at various road speeds. Next was the Fuel Max, which produced a few distinct tones as it cruised along at higher speeds. The dB Super E-spec and Integrity produced minimal tread noise, but were marked down for impact noise when they encountered larger bumps and patched sections of pavement.

    While not focused on handling, the personality and drivability of the Prius can also be affected by what tire is installed. The firm ride of the dB Super E-spec paid back with a quick, athletic feel as it responded crisply to driver inputs. So, too, did the Ecopia EP100 that displayed a responsive and linear feel to the steering. This came as no surprise as these tires were the only H-speed rated, Grand Touring Summer tires in the test and didn't require heavily siped, all-season tread designs to provide traction in light snow. Handling of the HydroEdge with Green X was pleasantly close to the first two tires, with its taut steering and connected feel when driving straight ahead. The Energy Saver A/S followed with somewhat slower steering response and just a hint of vagueness to initial steering inputs. The handling of the Fuel Max was appropriate for the category, but not overly responsive. Our team found the soft ride of the ComforTred resulted in a less-responsive tire, feeling slow to respond to driver inputs. The Integrity rounded out the group, feeling a bit sluggish when responding to driver inputs.

    What We Learned on the Test Track

    Our track test was designed to measure each tire's straight-line and steady-state cornering traction in wet and dry conditions. We used our track's in-ground sprinkler system to provide consistent wet conditions on the first track test day, followed by dry conditions on the second.

    One driver tested all of the tires back-to-back on one car to eliminate differences in driver skill and vehicle variables from influencing the outcome. The OEM tires were run first, last and in the middle of each day's sequence to allow us to identify and account for any changes in the test conditions.

    Braking

    We measured ABS-assisted braking distances from 50 to 0 mph to determine each tire's straight-line traction. We ran multiple stops measured by a Vericom VC2000 braking test computer and averaged the results to determine each tire's typical stopping distances.

    In wet braking all of the aftermarket tires stopped in distances ranging from 105.2 to 112.5 feet, however the OEM tire was separate from the aftermarket pack when it turned in a long 131.8-foot stopping distance.

    [fimg=left]http://www.cleanmpg.com/photos/data/2/2009_Toyota_Prius-II_5.jpg[/fimg]
    Column1Column2Column3
    Tire LineDry Braking Distance (in feet)% over/under vs. OEM
    Goodyear Integrity96.7 ft.---
    Yokohama dB Super E-Spec97.2 ft.+0.5%
    Michelin HydroEdge with Green X97.3 ft.+0.6%
    Michelin Energy Saver A/S98.3 ft.+1.6%
    Goodyear Assurance Fuel Max99.1 ft.+2.5%
    Bridgestone Ecopia EP100101.2 ft.+4.5%
    Goodyear Assurance ComforTred101.2 ft.+4.6%

    In dry braking, the OEM tire held a slim advantage ahead of all the
    aftermarket tires by turning in a 96.7 foot average. All of the
    aftermarket tires were close, ranging from 97.2 to 101.2 feet.​

    [fimg=left]http://www.cleanmpg.com/photos/data/2/2009_Toyota_Prius-II_4.jpg[/fimg]
    Column1Column2Column3
    Tire LineWet Braking Distance (in feet)% over/under vs. OEM
    Bridgestone Ecopia EP100105.2 ft.-20.2%
    Goodyear Assurance ComforTred106.7 ft.-19.0%
    Michelin Energy Saver A/S107.2 ft.-18.7%
    Yokohama dB Super E-Spec107.6 ft.-18.4%
    Goodyear Assurance Fuel Max108.7 ft.-17.5%
    Michelin HydroEdge with Green X112.5 ft.-14.6%
    Goodyear Integrity131.8 ft.---

    In wet braking, the OEM tires braking distances were significantly longer
    than all of the aftermarket tires by turning in a 131.8 foot average. All of
    the aftermarket tires were close, ranging from 105.2 to 112.5 feet.​


    Cornering

    We measured how fast the Prius could be driven around a 200-foot diameter circle to determine each tire's cornering traction. We timed both clockwise and counterclockwise directions and calculated average cornering values in g-forces of lateral acceleration, with higher numbers indicating better traction.

    [fimg=left]http://www.cleanmpg.com/photos/data/2/2009_Toyota_Prius-II_7.jpg[/fimg]
    Column1Column2Column3
    Tire LineDry Cornering (G-force)% over/under vs. OEM
    Goodyear Integrity0.804 G’s---
    Yokohama dB Super E-Spec0.798 G’s-0.7%
    Michelin Energy Saver A/S0.795 G’s-1.1%
    Michelin HydroEdge with Green X0.795 G’s-1.1%
    Goodyear Assurance Fuel Max0.775 G’s-3.6%
    Bridgestone Ecopia EP1000.769 G’s-4.4%
    Goodyear Assurance ComforTred0.743 G’s-7.6%

    In dry cornering like in dry braking, the OEM tire held a slim advantage
    ahead of all the aftermarket tires by turning in an .804 g average. All of
    the aftermarket tires were close, ranging from .798 g to .743 g.​


    In wet cornering the aftermarket tires again led the pack, generating average g-forces of 0.677 to 0.638 g. However our wet cornering test again saw the OEM tire separate itself from the aftermarket pack with its low 0.601 g of cornering capability. In addition to delivering low g-forces, great patience was required on the part of the driver for the OEM tire to recover grip every time it exceeded its limit.

    [fimg=left]http://www.cleanmpg.com/photos/data/2/2009_Toyota_Prius-II_6.jpg[/fimg]
    Column1Column2Column3
    Tire LineWet Cornering (G-force)% over/under vs. OEM
    Michelin HydroEdge with Green X0.677 G’s+12.6%
    Yokohama dB Super E-Spec0.670 G’s+11.5%
    Bridgestone Ecopia EP1000.661 G’s+10.0%
    Goodyear Assurance Fuel Max0.653 G’s+8.7%
    Goodyear Assurance ComforTred0.641 G’s+6.7%
    Michelin Energy Saver A/S0.638 G’s+6.2%
    Goodyear Integrity0.601 G’s---

    In wet cornering like in wet braking, the OEM tire was at a significant
    disadvantage behind all the aftermarket tires by turning in a .601 g
    average. All of the aftermarket tires were close, ranging from .677 g to .638 g.​


    Conclusion

    Tires shouldn't be considered as an afterthought as just round and black. They've always made important contributions to vehicle handling, traction and comfort. And while today's newest low rolling resistance tires are designed to be lean and green, this test has shown many of them can enhance vehicle fuel economy without sacrificing traction.

    And as you can see from the top-rated tire in each characteristic we evaluated, many of the tires' names essentially identify their intended strengths.
    While the Goodyear Integrity O.E tire may have offered state-of-the-art low rolling resistance, fuel economy and traction when it was first developed for the 2004 Prius, its continuing O.E. use essentially froze its specifications. That prevented it from adopting advances in tire design, raw materials and manufacturing methods developed in recent years that have been applied to the newest generation of eco-friendly, low rolling resistance aftermarket tires in this test.

    Tire Rack recommends drivers select tires based on their personal needs. Get tires that match:
    1. What you drive — Select the tire size and load range that matches your car, van or truck and offers appropriate load capacity to carry the weight of the vehicle, occupants and luggage.

    2. Where you drive — Select all-season, summer, winter or on-/off-road tires that match the weather conditions and terrain you expect to encounter. You'd probably forget all about a tire's contributions to fuel economy if you can't make it up a snow-covered hill or slide off an icy road driving summer tires in winter conditions.

    3. How you drive — Select passenger, touring, performance or light truck tires that will respond to your personal driving style. Basic tire categories help identify different combinations of comfort, handling and traction. Start your selection with the most appropriate tire category for you.

    4. How efficiently you drive — Select long-wearing and/or low rolling resistance tires that will give you the miles and/or miles per gallon you desire. But never forget that your vehicle choice and driving skill can influence how much fuel your vehicle consumes each year more than the tires you select.
    Not all of today's tires are created equal as some roll more easily than others and consume less energy. This means vehicles equipped with lower rolling resistance tires can achieve better fuel economy than if fitted with higher rolling resistance tires.

    The difference between our best and worst fuel economy may not seem like a lot, but it represents a real difference in fuel consumed over time. And while these relatively small percentage improvements in fuel economy may not appear significant, we could significantly reduce fuel consumption and environmental impact if every one of America's 250 million light duty vehicles improved its fuel economy by just a few percent.

    While tires have always played an important role for all types of drivers, the manufacturers have just successfully added some more green to the traditional round and black!

    CleanMPG contributed to this report.
     
  2. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Amazing! This is WONDERFUL information, and thanks to everyone who had a part in it.
     
  3. dr61

    dr61 Well-Known Member

    Another great job by the Tire Rack testers. Shows again what a black art tire design is...
     
  4. vtec-e

    vtec-e Celtic MPG Warrior

    Well done to all that made this possible. That was some undertaking.
    It's just a pity there wasn't a "for the hell of it" test at higher pressures, just to see....

    ollie
     
  5. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Ollie:

    ___Some time on the TireRack test track using our own baseline conditions, some additional standardized tests and to include our own HCH-II, Prius-II and Prius-III has been requested... That is about all I can say for now ;)

    ___John and the TireRack team did a spectacular job on this report and CleanMPG additions were minor by comparison. Bradlee from the MiHG was one of the initial contacts as well.

    ___Good Luck

    ___Wayne
     
  6. Damionk

    Damionk DWL Lover

    Great article. I am looking for tires right now and the Hydroedge with GreenX is one of the ones I was looking at. Too bad that, the Integrities, and the Assurance ComfoTred are the only ones that would fit on my car. I think this has helped me make up my mind on what to get.

    One question though, were the tires broken in a little before doing the FE test or where they brand new?
     
  7. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Damion:

    ___All tires including the OEM Integrity’s had less than 100-miles on them before the FE, braking and cornering testing began.

    ___Additionally and not in the report, the Integrity’s at MAX sidewall (44 psi) had ~ the same wet braking distances as the OEM’s at 37/35. In the dry, it is (expected) that the higher pressures would allow even shorter braking distances but that was not tested nor within the scope of the TireRack report.

    ___Good Luck

    ___Wayne
     
  8. Damionk

    Damionk DWL Lover

    In my opinion, not that it means much here, because they started with so few miles on the tires it very nearly negates the FE test as they were only 650 miles by the end of that portion of the test. That is about how long it would take to break them in. Hopefully they let you use the track and you can use some tires that are broken in a bit.

    Are you saying that the OEM's (Integrity's) had the same wet breaking distance regardless of pressure?

    FYI: I am leaning towards the Hydroedge.
     
  9. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Damion:

    ___TireRack had to have a baseline to work from and what better baseline than all sets of tires being brand new and not yet scrubbed.

    ___In our experience, it takes a few thousand miles, not a few hundred before a tire is well broke in and scrubbed to the vehicle on which it was installed. With ever increasing miles, the RRc usually falls a small amount in concert.

    ___The GoodYear Integrity's braking distances in the wet were ~ equal regardless of pressure. They were only tested up to OEM MAX sidewall of 44 psi however.

    ___Good Luck

    ___Wayne
     
  10. WriConsult

    WriConsult Super Moderator

    Truly awesome report, though I'd echo vtec-e's disappointment in their not doing a "what if" test of higher psi. I'd bet 48psi vs 35 might yield a bigger difference than one tire vs. another in some cases.

    In any event, great stuff. Interesting to see how the Integritys are really lousy in the wet compared to all of the other tires they tested - in my part of the country this is the biggest performance factor for about 8 months of the year. The Michelin Energy Saver looks like the best choice of the bunch for my needs.
     
  11. WriConsult

    WriConsult Super Moderator

    Good point about tire break-in. I've found that a tire's behavior can change drastically after they break in -- usually for the worse, in the case of OEM tires. On several occasions I've bought new cars that cornered great when brand new but squealed in corners like stuck pigs after a few hundred miles. The offenders were Goodyear Invicta, Firestone FR480 and FR680. Made me wonder if the tires had an outer layer of "sticky" rubber to make them seem great on the test drive, but quickly wore down to cheaper rubber underneath.

    Presumably this is less likely with the mostly non-OEM tires in this test. I haven't noticed the same phenomenon with any aftermarket tires I've bought, and there have been a lot of those.
     
  12. Damionk

    Damionk DWL Lover

    Yeah, I can understand needing a baseline. But, I think most here would agree that a "scrubbing" of around 1000 miles would be sufficient. I would imagine that the tires would be scrubbed at different rates due to different materials used in the tire making process. That I would think would give you differing RR during the break in process.

    Thanks for the clarification on the Integrity's.
     
  13. bestmapman

    bestmapman Fighting untruth and misinformation

    Great report. It is good to see CleanMPG getting involved with very useful reports like this.
     
  14. krousdb

    krousdb NX-74205

    Wayne,
    I have heard many times that the OEM Integrity (tires that were on the car when it left Japan) are different than the aftermarket Integritys that you can buy on Tire rack as replacements. The OEM tires are supposed to be LRR while the aftermarket tires are not. Can you confirm that what was tested were the original LRR tires, not aftermarket?

    I am on my 4th set of Integritys. I made a point of buying them slightly used from dis-satisfied Prius owners.
     
  15. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Dan:

    ___I will try and find that out for you...

    ___Another data point about the Integrity's... I know they are not so good in the wet and snow but the Corolla's Integrity's were replaced at 65,000 with another set of Integrity's and the second set is out over 110K now with another what appears to be 30,000 left to go. 50 - 70 psi has been the second sets life and the wear is dead even all the way across.

    ___Dan, you are running through them every 35 to 40K even with higher pressures on your Prius-II?

    ___Good Luck

    ___Wayne
     
  16. krousdb

    krousdb NX-74205

    I run them well over the max sidewall. The wear is on the edges, with not so much wear in the middle. What you would expect from underinflation. Iv'e had two sets of integrity's, each gave me 45k miles. Then I had a set of Kumho's for 45k miles with lots of tread left but changed them for the Conti's hoping for better FE. But the Conti's were terrible and I went back to a third set of Integrity's, which lasted for 45k miles again. I'm now on the 4th set but seriously considering the Ecopia. That is why I asked about which Integrity was tested. If it was truly the OEM tire that was tested, I might have to order a set of Ecopias.
     
  17. CapriRacer

    CapriRacer Well-Known Member

    First, Wayne, you are to be commended for the effort. This is about as good a tire comparison as I have seen.

    2 points: I have been critical of Tire Rack's wet traction testing because it produces fairly high skid numbers - just like this one did. I think this is because of the depth of the water - not deep enough to get the tires to start hydroplaning.

    Ordinarily, this would be a fault. But in this case, you want to be testing only the rubber compound - not the tread pattern - so the water depth is appropriate for the comparison that was done.

    I have noticed that many tires for Japanese based car manufacturers have many poor wet traction complaints - something you don't get so much of for US and European based car manufacturers. I suspect this is because the Japanese based car manufacturers do their traction testing in Japan - even the tires from US and European based tire manufacturers. I further suspect the road surface they test on in Japan to be quite different than the road surfaces tested on in the US and in Europe. I am sure some of the inconsistency within the rankings for traction derive from this.

    Background: Tread rubber compounding is such that the road surface itself can have a major influence on traction results. You can get reversals in rank order by testing on different road surfaces.

    I strongly suspect the Goodyear Integrity used as a control suffers more from the Japanese connection than the advance in technolgy as speculated by Tire Rack.

    For those who are unaware: Trying to compare tires that come on different vehicles is a lesson in futility - unless you know what each car manufacturer's specs are. On top of that, every vehicle platform will have a different spec.

    So trying to base what the 185/65R15 Goodyear Integrity used on the Prius performs compared to what appears to be the same tire that comes on the Corolla - well, be very careful. These tires were designed indpendently of each other and they can be completely different.

    And one last point: Tire wear wasn't measured in any way. This is quite understandable since tire wear testing - at least the kind that has meaning - is fairly expensive.

    UTQG ratings are somewhat helpful, but the marketing department and the warranty department within each tire manufacturer battle of how to do them. The end result can be quite different between manufacturers. The only way to be sure what the wear is like for a given tire is to perform a test.

    But overall a good and meaningful result - Congratulations!!
     
  18. ioverholt

    ioverholt Member

    This is great!

    I had noticed a surprising lack of tire talk on the forums. Rolling resistance has a huge effect on FE and so I figured there would be many discussions about tires. I guess everyone has not had their cars long enough to need tires.

    I was going to start a thread on tires because I need new ones for my HCH-II before it gets wet. I have been intrigued by the new Yokohamas since I saw their claims about lower RRc and higher traction. After seeing the results, I am definitely going to buy the dB Super E-Specs. The tire improves on FE and handling relative to the stock tires. That is EXACTLY what I was looking for.

    Although from the results it does not look like you could go wrong with the Michelin Energy Saver A/S or the Bridgestone Ecopia EP100.

    Personally, I like to take turns at about the same speed as straights. :D I autocross an MK1 Scirocco for fun, so I know a thing or two about turning. I'm just not impressed by drivers who drive fast in a straight line, but almost stop when there is a turn (most SUV drivers). If you can't make a turn at your straight-line speed, then you really don't have any safety margin.

    Thanks for the great article!
     
  19. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    There wasn't much talk because there was almost zero data until now. It's pointless to speculate when you have nothing concrete to discuss. We know very well how much tires affect *everything*, and now we have some data to discuss.
     
  20. warthog1984

    warthog1984 Well-Known Member

    If you make a turn at straight-line speeds, you're gonna bend something.

    Oh, you meant the OTHER Autocross:D

    We don't need no stinkin' parking lot
     

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