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Any tire pro's here? Tell me about aspect ratio

Discussion in 'Off Topic Threads' started by Porcupine, Jan 18, 2011.

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  1. Porcupine

    Porcupine Active Member

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    South Central Massachusetts
    Any tire pro

    My current car (Ford Taurus) takes a 215/60R16 tire. I have some barely used 225/55R16 tires. I don't think the 10mm difference in the section width will matter very much (correct me if I'm wrong), but I'm not sure about the aspect ratio. Will the '55' tires work OK on the '60' rim? Thanks for any help.

    LA in MA
     
  2. Hawk46

    Hawk46 TS Member

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    Jan 7, 2011
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    Any tire pro

    Shouldn't be a problem. Mount one and check for tire clearance at full turns left and right. If that's good, should be all good.
     
  3. scdrch

    scdrch TS Member

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    Aspect ratio is the height of the sidewall as a percentage of the section width.

    Example... 215 is the section width in millimeters, the sidewall height is 60% of 215....and 16 is the wheel diameter.

    The 225/55/16 tires should work ok as the general rule is for every 10mm increase in section width requires a decrease of 5 in aspect ratio. This would be considered a "Plus Zero" sizing for your vehicle. The overall height of the 225/55/16 tire is most likely a fraction less than the overall height of the 215/60/16. Depending on the vehicle, many newer models can "learn" a new tire size and adjust the speedometer, odometer etc., throught the vehicles ECM.

    To err on the side of caution, when going to a wider tire there is a possible increase in the tendency to hydroplane and possibly reduce traction in snowy conditions, however thre dry braking and cornering ability are generally increased.

    As for the number of plies, most if not all passenger tires today have 2 ply sidewalls and 3 ply tread. Truck tire that are designated LT may have 3 ply sidewalls and 4 ply treads, of course these are much thicker than in passenger car tires. The days of true 6,8,10 ply tires have all but disappeared. E load range truck tires will carry the same load as the old ten ply tires, but they do not have 10 plies in them.This applies to radial tires, not bias ply tires.

    Hope this helps.
    Dean Reichel....8 years of tire selling, Michelin certified.
     
  4. CalvinMD

    CalvinMD Well-Known Member

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    I'm in real trouble then...my Vette has 325/35/17's...they could plane across an ice cream wrapper
    [​IMG]
     
  5. Edbird99

    Edbird99 TS Member

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    Make sure you change all four tires-not two different sizes on front and back.I got a deal on a set of Vette rims and tires for my Tans Am-17's in front,18's in rear.However, due to different overall tire diamater,the ABS kept kicking in during braking thinking a couple of tires were operaing at different speeds.To fix, I had to finally change a pair of tires with a pair having a different aspect ratio to match overall diamater.So my advice is all or none.
     
  6. TomB

    TomB Member

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    I just happened upon the thread and am curious to know what the actual definition of "section width" is, as it pertains to tires. If one takes 215mm and divides by 25.4mm/in, that comes out to 8.5 in. Is that the tire width ??
     
  7. short shucker

    short shucker TS Member

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    TomB,

    Yeah kinda. This distance seems to vary from manufacturer to manufacturer, but it is close.

    porcupine,

    The tires will work just fine. They won't work quite as good in the snow as the wider the tire gets the less it is able to dig down and grab ahold of the road. The ride may suffer a bit do to the increased sidewall stiffness. Depending on the tread design, they may have a tendency to follow rain grooves a little more.

    ss
     
  8. slic lee

    slic lee Active Member

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    Go online to the website of the tire co you have now, go to specs, write down specs, go to other co and check specs on the tire your thinking about. If thats to much trouble, go to TIRE RACK web and check out.
     
  9. Bruce Specht

    Bruce Specht Well-Known Member

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    Make it easy on your self, go to the Tire Rack web site check the overall diameter. That is really your concern for the ABS as for will the 55 vs 60 series work on your current wheel width the answer is yes. You need to be concerend if you change OD by more than 10% as it will affect the ABS. Dean gave you valid information. The 60 series will be a bit taller than the 55 series. The 55 will deliver greater dry handeling but you will loose wet and snow traction. I spent 30 years in the industry last three years as a Director for the International Tire and Rubber Association.
     
  10. scdrch

    scdrch TS Member

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    Calvin MD--don't worry about those tires on your Vette, they can handle the rain and that's not an ideal snow car anyways, correct?

    As for section width, the formula mentioned above by Tom B is correct, but the actual section width is measured from where the sidewall meets the tread, (there is a line where they meet) across the face of the tread to that point on the opposite sidewall. So yeah the section width may be 8.5 inches when doint the math but only 7.5 inches of tread is actually meeting the road depending on the design of the shoulder tread blocks.

    Tires were so simple when I was growing up at the local gas station. All you had to know was that F60-15's went on the back of your uncle's Chevelle and some skinny 14's on the front if you wanted to go fast ina straight line.

    Thanks for the convo guys.
    Dean Reichel
     
  11. HDLLLIII

    HDLLLIII Member

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    your best bet is to google tire size calculators, overall diameter, rolling distance. and compare tire sizes in regarding revs per mile as this will affect shift points etc. these computers in cars these days don't like being tricked. more than 1-2% difference in sizes will have more dramatic effects than you might suspect
     
  12. h92064

    h92064 Active Member

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    Here you go - easy to use tire calculator tool - to compare tire sizes -

    http://www.discounttire.com/dtcs/infoTireMath.dos

    This allows you to enter the original tire size on the left, the new tire size on the right (with explanations below regarding all of the measurement dimensions), and then click on the "Select/Compare" button. It will output a nice/complete comparison, including what (if any) difference there will be in the speedometer reading, assuming it was accurate with the original tire size provided.
     
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