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Thread: Rather clueless about passenger car tires... quick size up question (lower motor RPM)

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    Rather clueless about passenger car tires... quick size up question (lower motor RPM)

    A normal tire size for me is 37-13.5-15, so it's safe to say I'm not familiar with passenger tires.

    Finally bought a Micra, and cant believe how horribly geared the car is. Its pulling 200rpm higher than my 3 cylinder Mirage in the highway, and fuel economy past 85km/h drops very sharply.

    Looking to reduce gear ratio by about 10-15%. I know roughly what size this tire will need to be, but I have no idea what a standard sized tire would be. Looking to keep as much sidewall as possible due to horrible local roads as well.

    Is a 205/65/16 a thing? Having trouble sorting out common, cheaper tires versus one off expensive ones.

    Took a peak under the car, and a tire about that size should clear just fine with a bit more offset rims.

    Also if anybody had ever rammed a 6speed into these or done a regear, that's also an option. I just cant understand why its pulling 3200 at 100.


    Last edited by nickels; 02-17-2019 at 09:11 AM.

        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


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    look at :
    https://www.willtheyfit.com
    and put various sizes in until you find what will work for you.

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    Yes, our SV auto revs too high on the highway. I had some new 185/70/14 winters that I put on this winter. A little taller than stock. I canít see much taller as fitting without rubbing. I might try some 185/75/14 - I have a few of those kicking around. If you want to stay 15Ē you could try 185/65/15. If you go wider, you wonít likely save any gas due to increased resistance/ friction. Trial and error w/ tires and wheels can get expensive real quick.
    Last edited by Mel; 02-17-2019 at 08:10 PM.

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    MetroMPG (02-19-2019)

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    Administrator MetroMPG's Avatar
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    Hey nickels - congrats on your new Micra!

    Nobody has re-geared a Micra here yet. Pretty big job, right?

    I know of people who have swapped a taller 5th gear set in some cars. Changing just 5th gear is relatively easy compared to a complete trans swap, since the 5th gear set lives outside the main transmission case, under a stamped steel cover. You just remove that cover, unbolt the gears and install the new set.

    Thing is: someone has to do the legwork to find which other Nissan transmissions have better ratios, also have the right spline pattern for the gears, and also have the same input/output shaft spacing as the Micra's gearbox.

        __________________________________________

        click to view fuel log View my fuel log 2015 Micra S manual: 5.0 L/100 km ... 56.5 mpg (Imp) ... 20.0 km/L ... 47.0 mpg (US) ...


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    Senior Member Azmodon's Avatar
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    if you're a massive nerd, in addition to 'willtheyfit' ... http://paws.kettering.edu/~amazzei/tire_calculator.html

    Find out and plug in everything you can - compare your stock tire's patch to your new one, when you find a combination that causes the patch to get shorter (front to back) without getting >130% of that amount wider (side to side), you'll have less rolling resistance as there's less deflection. Stock we have a 5.5/6" rim with 185/60, the amount of ballooning the face does gives the same contact patch width to the same tire compound at 205/45 running on a 7.5" rim

        __________________________________________

        click to view fuel log View my fuel log 2015 Micra SV automatic: 7.1 L/100 km ... 39.9 mpg (Imp) ... 14.1 km/L ... 33.3 mpg (US) ...


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    Thanks for the advice all. I'm in a unique situation of complaining about fuel economy for aure.

    Mirage does 5 at 90, 5.5 at 100.
    Micra does 6.5 at 90, 7.2 at 100 (yes it's cold here)
    Factor in that the Micra has exactly 4/3rd the engine, and the numbers line up, however I know its capable of a bit more. Am enjoying the extra power though. Still slow, but a bit less scary slow.

        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


  8. #7
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    I actually return 10l/100 for the first 10km of my commute as the car warms up. Stupid -25C weather.

        __________________________________________

        click to view fuel log View my fuel log 2018 Micra SV manual: 6.8 L/100 km ... 41.8 mpg (Imp) ... 14.8 km/L ... 34.8 mpg (US) ...


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    Senior Member MrMicra2015's Avatar
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    do 90 not 100 ?...especially if you live in squamish!....lol....i get never under 6 and never over 7 according to nissan gauge. mines manual though. Ive played with tire diameters..205/40/17....205/45/16... im looking to rev MORE for better acceleration.....obviously it doenst make a huge difference in my estimation...is the 5th gear Really on the outside metro ?....i never knew that.
    2015 Micra S (manual)
    no A/C /no power options
    Feb 2015 build
    9,999 purchase price + tax..no additional 1600$ because it was a 2015 purchased in 2016
    so receipt says $8,399....+1600 .... so they look good i guess...for a brand new car!

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    You could just get some of these beasts:

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    https://www.amazon.ca/Universal-Stai...motive&sr=1-33

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    Hii i am willing to change tires of my car basically i have 2 vehicles first one is Micra and 2nd one is truck I have Ram 1500 truck i am willing to change both tires do you have any recommendation for me that wich tires are better for both, The ram truck i use for 24/7 towing service so need durable and reliable tires for the truck.



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