Mileage Question

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  #1  
Old 04-26-11, 04:13 PM
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Question Mileage Question

I have oversize tires that boost my mileage 11% vs. original tires. Is this a dumb way to get better mileage? It's a manual trans. and I drive conservatively.
 
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Old 04-26-11, 04:24 PM
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Taller tires are fooling your odometer into thinking you are getting better mileage. You may somewhat, but it's not a way to guarantee it. Wider tires tend to have more drag, so less mileage. You said oversized, so not sure if they are taller, wider, or both. There are trade offs.
 
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Old 04-26-11, 07:59 PM
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well, you do cover more distance with a larger diameter tire under the same rpms. your speedometer will not be true and some can be re-calibrated. i'd say, if it's safe and works for you - why not.
 
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Old 04-27-11, 04:57 AM
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"Taller tires are fooling your odometer into thinking you are getting better mileage"

Actually it's the other way around. Since it takes less revolutions for the tire to go a mile, your odometer will only show about .9 of a mile for each mile run. You'd need to add 11% to the miles to accurately figure your mileage.

Since your are more or less changing the gearing of the vehicle, a lot depends on the vehicle and engine as to how it will effect fuel mileage.
 
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Old 04-27-11, 06:25 AM
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Taller tires, and mileage verified with GPS. I just have to remember the speedo is off!
 
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Old 04-27-11, 07:22 AM
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I don't understand your question. If indeed you changed tires and got 11% better mileage, that's great... why would it be dumb?
 
  #7  
Old 04-27-11, 09:00 AM
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Using taller tires is no different than having an overdrive gear to slide into. Most vehicles would not object to the change on the low end and the high end simply moves your shifting points a bit.

However, I suspect your actual improvement is as much a result of careful driving, awareness, as it is to the change in tire size. The old overdrive option was typically for use once you got up to highway speeds.

But no matter, as 2granddaughters said, if it works for you, 11% is great.

Bud
 
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Old 04-27-11, 10:21 AM
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The issue with using a larger diameter tire is the speedometer and odometer will be off - already said and you know about it - and the gearing of the car changes with every gear becoming taller such that you could have a situation where you would not have enough power but you would have already encountered that by now. So, I say keep with it.
 
  #9  
Old 04-27-11, 02:37 PM
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Boy do I feel dumb
I misread the original post and thought the speedo was off 11%, didn't comprehend that was the increase in mpg.

I've had several 4x4s with oversized tires. While they often look bettr with bigger tires, I don't know that it helped the mpg any....... if it did, I'd hate to buy the gas with little tires
 
  #10  
Old 04-27-11, 03:54 PM
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It's definitely not a performance vehicle, but the trade off of mileage vs. acceleration is worth it.
 
  #11  
Old 04-28-11, 05:45 PM
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If you want better mileage by changing rims and tires you need to reduce spin loss. In order to reduce spin loss you need lighter and smaller diameter wheels. That will increase your mpg a little. Larger diameter tires will hurt your mpg. If you have a calibrated odometer. Low rolling resistance tires that typically have a UTG of 500 or greater will last longer and give better mileage without the need for new rims. Its a harder rubber so you lose some traction in winter.
 
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