A good tire size swap for ride and mpg?

Discussion in 'Technical' started by fudggj, May 16, 2008.

  1. fudggj

    fudggj New Member

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    Greetings...
    I have a daily driver 73 Maverick (all stock) with a 200 ci six, C4 automatic transmission, rear axle ratio 2.79:1. The car originally came with 6.45x14 tires on 4 1/2 inch rims with zero offset. (The 6.45x14 tires correspond to the size of the current P175/75R14 tires) I am thinking about converting to 5 inch rims with a set of P205/75R14 tires. The 5 in rims have a 5/8 in offset inward (that is, moves the tire toward the car's center) compared to the original 4 1/2 in rims zero offset. I have checked clearances and there doesn't seem to be any problems there. Possibly someone else out there has tried this. Two questions: 1) Am I likely to have any problems with the suspension or anything else if I make this change? (other than making the speedometer and odometer read a little low.) 2) Should I get a little better ride and a little better mpg with this change? Note, I just use this Maverick for my main mode of transportation and rarely, if ever, get the car over 60 mph. Thanks for replies.
     
    Last edited: May 16, 2008
    fudggj, May 16, 2008
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  2. scooper77515

    scooper77515 No current projects.

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    Stock gears? 2.79?

    There are several calculators on the internet where you can put in the numbers and it will tell you what rpm you will be doing at various speeds. You can then decide what you can live with...

    The one at the bottom of this page is what you need to calculate tire size. Use 1 for transmission ratio and the trans cas ratio, I am pretty sure that is the top gear ratio of the stock transmissions.

    http://www.4lo.com/4LoCalc.htm
     
    scooper77515, May 16, 2008
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  3. tim keck

    tim keck truckdrivintrailertrash

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    I'd go with a 195/75 tire,the 205s are a bit taller and will make your speedo show slower than you're actually going,because they will change your "effective" gear ratio.Not much,but probably enough to make it show about 2-4 mph slower than actual.Ride,drive,clearances should be just fine though.
     
    tim keck, May 17, 2008
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  4. Dean Deeter

    Dean Deeter Member

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    Hey Fudgge,
    Were you located at in Ohio??
     
    Dean Deeter, May 17, 2008
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  5. PaulS

    PaulS Member extrordiare

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    Use the skinniest tire you can at the highest pressure that is safe in order to get the best economy. It will not give you the best ride or performance but it will give you better fuel economy by reducing the rolling resistance.
    There is a trade off when you try to get a decent ride or more performance. You have to give up some economy in order to get a better (smoother) ride or to get the tires sticky enough to improve handling. You have to decide where your priorities lie.
     
    PaulS, May 18, 2008
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