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Thread: Tire size ?

  1. #1
    Motorcyclist patiodadio's Avatar
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    Tire size ?

    Its time to put tires on our 2012 Mini, we have OEM 175/65 15's on it now and the speedo is off by about 4 mph (fast) at 70 mph. Would 185/65 help heal the speedo or make it worst ?
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  2. #2
    Outlander Omega Man's Avatar
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    I don't know but experience has shown me that the "newer" vehicles speedometers trend on the high side with the actual travel speed being on the low side....It sounds like it's still under warranty being a '12, perhaps the dealer can make the adjustment to the computer to bring it on.
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    Last edited by Omega Man; 08-11-2014 at 01:01 AM. Reason: clarification
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  3. #3
    Registered User lkraus's Avatar
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    Actual diameters vary by tire brand and model. http://www.tirerack.com lets you check the diameter and revolutions per mile of most currently available tires, so you can compare your current tires to the new ones you are considering.

    I don't think I've ever had a vehicle with a truly accurate speedo, they all read higher than actual speed. I used to time mile markers on the interstate until I knew how far off my car was indicating and then just added the appropriate correction. Today, I just use a GPS until I know how the car lies. In our Camry, if the limit is 70, I know I'm legal at an indicated 73.
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  4. #4
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    THEORETICALLY, a 185/65-15 should be 2.1% larger in circumference than a 175/65-15.

    THEORETICALLY, that should increase your actual speed from 66mph to 67.38 mph at an indicated 70 mph.

    THEORETICALLY, your gas mileage should increase by 2.1%.

    THEORETICALLY, your acceleration will be a hair worse due to higher effective overall gearing.

    THEORETICALLY, your cornering should be better due to wider tread width.

    BUT, as Larry states, ACTUAL dimensions vary by brand and model. TireRack is a very good resource for finding ACTUAL dimensions.

    But, the answer to your question is; YES, that would be going in the right direction, but it wouldn't correct it by that much.




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  5. #5
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    In KY the State cops stop you @ ~9 over so you have a nice cushion as it is.
    I'd never choose a tire based on the speedo. Too many other more important factors like staying on the road. Use the tires being replaced as a guide-were they all you ever wanted or lacking in some way? Mileage and traction and handling?
    +1 size is the way many go with performance in mind but not always the best for the suspension when stock. Mini forums should provide more than you ever want to know as tires & wheels are "the" topic on car forums. Best price?-lots of luck cause tires are hard to buy on the cheap.
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  6. #6
    Motorcyclist patiodadio's Avatar
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    Quote Originally Posted by 98lee View Post
    THEORETICALLY, a 185/65-15 should be 2.1% larger in circumference than a 175/65-15.

    THEORETICALLY, that should increase your actual speed from 66mph to 67.38 mph at an indicated 70 mph.

    THEORETICALLY, your gas mileage should increase by 2.1%.

    THEORETICALLY, your acceleration will be a hair worse due to higher effective overall gearing.

    THEORETICALLY, your cornering should be better due to wider tread width.

    BUT, as Larry states, ACTUAL dimensions vary by brand and model. TireRack is a very good resource for finding ACTUAL dimensions.

    But, the answer to your question is; YES, that would be going in the right direction, but it wouldn't correct it by that much.
    Thanks ! I really appreciate the info !
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  7. #7
    Motorcyclist patiodadio's Avatar
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    Quote Originally Posted by kantuckid View Post
    In KY the State cops stop you @ ~9 over so you have a nice cushion as it is.
    I'd never choose a tire based on the speedo. Too many other more important factors like staying on the road. Use the tires being replaced as a guide-were they all you ever wanted or lacking in some way? Mileage and traction and handling?
    +1 size is the way many go with performance in mind but not always the best for the suspension when stock. Mini forums should provide more than you ever want to know as tires & wheels are "the" topic on car forums. Best price?-lots of luck cause tires are hard to buy on the cheap.
    I'm on a couple of Mini forums but just wanted you guys 2 cents. I have been looking at lots of tire reviews. Like most BMW owners, I obsess over everything, oil, tires, etc. Why can't we just go buy tires or whatever and forget about it like everyone else ?
    Last edited by patiodadio; 08-12-2014 at 05:51 PM.
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