What would the FIST feel like with higher profile wheels/tires?

Discussion in 'Fiesta ST Wheel and Tire Upgrades' started by Mike, Oct 14, 2013.

  1. wash

    wash Active Member

    The series relates to sidewall height, not tread width or contact patch.

    Also, there are only two factors that determine contact patch area: vehicle weight and tire pressure.
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  3. WScottCross

    WScottCross Well-Known Member

    The first number in the tire size is the width (in millimeters), the second number is the sidewall height ratio (percentage of tire width) , the third number is the rim diameter. So a 45 series tire has more sidewall height than a 40 series. A 40 series will generally have less roll in the corners and give better steering response. Again these are generalities, there are alot of other factors that play into handling characteristics of tires.
  4. ST_Rocky

    ST_Rocky Member

    Most of my life with tires and racing, I always went with the widest, going by the middle number (skinny - widest: 65>60>55>50>45>40>35), and the first number the height of the tire (185>205>215>225>235>245>255, etc). So thus why I don't understand why most are not looking for a 215/40 or 225/40 size tire.
  5. WScottCross

    WScottCross Well-Known Member

  6. eRic

    eRic Active Member

    you have it backwards. the first number is section width of the tire in millimeters. the second number is the aspect ratio in percent of the width. the third number is the wheel diameter in inches.
    Smokin likes this.
  7. ST_Rocky

    ST_Rocky Member

    Thanks for clearing some of this up for me. But still, would not a 225/40 be wider, though shorter, than a 225/45? For if I got this right, the sidewall would be shorter, but the tread patch would be wider on the 40 series vs the 45, correct?
  8. wash

    wash Active Member

    Nope, same width.

    Well at least they would be if all the manufacturers stuck to the same width but they don't always do that.

    Now if you had a 225/45r16 on a 16*7 rim compared to a 225/40r17 on a 17*8 rim, the contact patch would probably be wider with the wider rim but that's because of sidewall bulge or whatever its called when you put a wide tire on a narrow rim.
  9. Smokin

    Smokin Active Member

    A 40 is 40% of the section width. A 45 is 45% of the width. So in relative manufacturing measurement terms, a 225/40 has a sidewall height (not tire height) of 90 mm. A 225/45 has a 101 mm sidewall, so it is taller but not any wider.....it's still a 225 mm section width. Not tread width.

    The 195/55x16 winter tires I have ordered would have a 107 mm sidewall height which is 55% of the 195 mm width. Double the 107, divide by 25.4 mm/inch and add the 16 inch diameter wheel/tire and voila, you get 24.4 inches. Exactly the advertised diameter of the tire...

    A 225/45x16 Dunlop Direzza is 23.9 inches tall. just as advertised...
    Last edited: Dec 2, 2013
  10. Mike

    Mike Member

    Just installed 205 45 16 with Conti DWS and I am a happy man. Now it's the perfect daily driver.
  11. limbo

    limbo Active Member

    What speed is top of second with those?
  12. Fistofthebrownstar

    Fistofthebrownstar New Member

    Should have been the stock size IMO. What's the weight on your 16" wheels out of curiosity?
  13. Mike

    Mike Member

    The website says 17.1 lbs. I believe the OEM's are 22 lbs. One of the entries on this
    The Tire Rack website says 17.1 lbs. I believe the OEM's are 22 lbs. PCA-1 on this discussion strip made a case that lower weight and diameter (total diameter is now .02 inches less than with the OEM setup) changes speedometer accuracy but could theoretically improve gas mileage. His argument made sense to me so I made the change to the 16" Conti set up. Regardless the ride is noticeably smoother (especially over bumps and highway joints) making my smile last longer after each drive.

    And isn't that what the purpose of this car is all about?
  14. stuntdoogie

    stuntdoogie Active Member

    Been riding on stock wheels with 205/45/17 All Season tires and its been alot easier on my ass. Dont notice much loss in cornering either for street. Im sure for track you would experience loads of rubber banding but since I dont track 45 series is where ill be sticking with untill I buy summer
    I will be getting the same setup in the spring with summer tires. Leaning towards Black 16" Rota Slips... cant wait!
    Firesail likes this.

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