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Light 16" wheels and mpg

Discussion in 'Gen 2 Prius Accessories & Modifications' started by chrisek, Jun 4, 2008.

  1. chrisek

    chrisek geek

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    Looking for this to spread information on what I worked towards and the results we found. Hope you find this helpful.

    I wanted to get some summer wheels that allowed performance summer tires. After reading about dismal 17" stuff I decided on 16"x7" width and 205/50/16 tires which allowed me a couple of options while maintaining a near stock circumference. Please keep in mind I have stock suspension other than the BT Tech Plate.

    So I got the lightest readily available wheels at a reasonable price that my wife liked (hows that for lining up the planets?) and got the Enkei RS+M which are rated at 14.5lbs for this size. For tires I went with Dunlop Direzza Z1 Star Spec.

    I wish I had weighed the tires or found some kind of rating for it. Our winter wheels are the stockers with Blizzak REVO-1's in the stock size. They are down to the wear bars so I am expecting them to be lighter than new ;). We reliably got 44-45mpg (commuting at 80-85mph) with these, and I really didn't know what to expect with the summer wheels thinking the winter tires to be heavy (with no info to back that up) but a larger rim meaning the circumference of the bead (heavy part of the tire) is larger and affecting the acceleration more.

    After 6 weeks we are solidly 42-43mpg, so roughly a 2mpg drop. If these tires are "heavy" then that would be something to look after on the next set.

    After I replace the snow tires this summer I will weigh the entire wheel of each setup (I do not have accurate scales, so I will round to the pound.) Also, pix to follow.

    As for handling, there is clearly more traction than the chassis knows what to do with. Time for me to get back in touch with Brian at BT Tech.

    Hope someone finds this useful.
     
    #1 chrisek, Jun 4, 2008
  2. F8L

    F8L Protecting Habitat & AG Lands

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    That sounds about right depending on your driving conditions.

    My 17" wheels were 14lbs also but the extra tire weight and stick compound killed my milage as I'm sure you've read.

    Last time I tried to use em I got a 45mpg tank with a high point of 47mpg during part of the tank. I swapped back to stock, ran one 54mpg tank and I am currently sitting at 57.1 with 182miles on the current tank.

    I think the key is to find a good LRR tire and give it time to break in. All tires will cause an initial drop in mpg but as they break in and wear down you reduce mass and RR goes down so mpg goes up. :) You are much more likely to find a LRR tire in a 16" than a 17" it seems. Which is why my 17's are on the shelf for now. :)

    Thanks for the writeup :)
     
    #2 F8L, Jun 4, 2008
  3. chrisek

    chrisek geek

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    What kind of rims do you have F8L? The lightest 17" rims I could find for my STI were Enkei RPF-1's (16lbs). I'd kill to lose the extra 2 (unless of course you are running those carbon Dymags.)
     
    #3 chrisek, Jun 4, 2008
  4. narf

    narf Active Member

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    Wheel/tire weight is only part of the equation. Wider tires, and softer squirmier rubber increase fuel consumption because they increase rolling resistance. (They also improve handling). I'm guessing the 205/50/16 on 7" rims have a wider footprint than the 195/55/16s that come stock on the Touring.
     
    #4 narf, Jun 4, 2008
  5. F8L

    F8L Protecting Habitat & AG Lands

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    Oops, they are rated at 15lbs. Sorry about that. Centerline Monsoon RPM


    Technical Specifications
    • 1-piece, Rotary Forged Wheel
    • Manufactured using highest quality T-6061 Billet Aluminum
    • 1200 lb. load rating per wheel w/ 26" max tire diameter
    • Center Line's FORGED wheel typically weighs less then your stock wheel translating into performance improvements including: (1) acceleration (2) braking and (3) fuel economy. Our 17" wheel weighs only 15 lbs!
    Seems about right. My tires are rated at 22lbs and my total combine weight on an accurate scale was 36-37lbs. That would leave the wheel at 15lbs. When I weighed the wheels at my shop they were 15lbs but I don't trust that scale.

    The General Exclaim UHP? tire is supposed to be one of the lightest so you might check them out.
     
    #5 F8L, Jun 4, 2008
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