1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Optional wheel/tires sizes with Navgation System?

Discussion in 'Gen 2 Prius Accessories & Modifications' started by a steinman, Dec 30, 2005.

  1. a steinman

    a steinman New Member

    Joined:
    Dec 30, 2005
    1
    0
    0
    I want to go with performance tires for summer, but the instructions for the Navigation System say the tire diameter is very important to keep the system accurate. Does anyone know what sizes are close enough that it will still work properly? The 185/65/15 standard tires have a diameter of 24.4 - 24.5". The 195-55-16 setup can be obtained at 24.4". But what I really want is 205/45/17, which varies from 24.0 - 24.4". The Avons that I would in this size are 24.2". This is about 99% of the original equipment. Can anyone help? Thanks so much.
     
    #1 a steinman, Dec 30, 2005
  2. vibeowner

    vibeowner New Member

    Joined:
    Aug 14, 2005
    4
    0
    0
    On the nav system you can tell it you got new tires, and it will recalibrate. Read about it in the nav book. I am considering going one size up for better ground clearance.
     
    #2 vibeowner, Jan 8, 2006
  3. BMcGraw

    BMcGraw Member

    Joined:
    Mar 27, 2004
    230
    4
    0
    Location:
    Southern California
    Here's some more info that might help (nothing related to recalibration unfortunately).

    The OEM's are 185/65R15's which makes them a 24.5" diameter. I'm running Nankang 205/40R17's which = 23.5" in diameter. They make my speedometer reading 4.1% too fast. When my speedo reads 60 mph I'm actually doing 57.5. I'm not sure what this does to my mpg calculations but I'm sure the weight of the non-stock wheel/tire combination adding 15 lb.'s each doesn't help any. My mileage drops by around 5 mpg from the looks of things. Of course my mileage also varies drastically from one day to the next since I'm not a very consistent driver. If someone tailgates me or gives me a dirty look for driving too slow (giving me the 50 mpg) my "I'll show you what this baby will do" attitude kicks in and I get more like 30!

    OEM Weight: 6.5kg (14.3# ea.)
    The Goodyear Integrities weigh 17 lbs, for a total of 31.3 lbs.
    Size: 15x6JJ, PCD 100mm, 5 Holes, offset 45mm

    The Goodyear Eagle F1 DSG3s weigh 22 lbs (5 lbs weigh penalty).



    Back to the diameter discussion, I'm actually considering going to Centerline brand 18" alloy wheels! (centerlinewheels.com) They're the same weight as the OEM wheels (about 15 lb's) and with 205/40R18's, the diameter is exactly the same.

    TIRE SIZE DIAMETER RELEVANCE
    185/65R15's = 24.5"

    205/40R18's = 24.5" SAME SPEED
    215/40R18's = 24.8" 1.2% too slow

    205/40R17's = 23.5" 4.1% too fast (Assassyn's I have now)
    215/50R17's = 25.5" 4.1% too slow

    235/40R17's = 24.4" 0.3% too fast
    205/45R17's = 24.3" 0.8% too fast
    215/45R17's = 24.6" 0.6% too slow
    205/35R19's = 24.6" 0.7% too slow

    or...

    Specification Sidewall Radius Diameter Circumference Revs/Mile Difference

    185/65-15 4.7in 12.2in 24.5in 76.9in 824 0.0%
    195/55-16 4.2in 12.2in 24.4in 76.8in 825 -0.1%
    205/45-17 3.6in 12.1in 24.3in 76.2in 831 -0.8%
    215/40-17 3.4in 11.9in 23.8in 74.7in 848 -2.8%
    215/45-17 3.8in 12.3in 24.6in 77.3in 819 0.6%
     
    #3 BMcGraw, Jan 8, 2006
  4. flynz4

    flynz4 Member

    Joined:
    Dec 17, 2005
    329
    13
    0
    Location:
    Portland, OR
    Vehicle:
    2015 Prius v wagon
    Model:
    Five
    I assume you are also losing about 4% of your warantee.

    /Jim
     
    #4 flynz4, Jan 8, 2006
(You must log in or sign up to post here.)