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Discussion Starter · #1 ·
i hade a stock nissan frontier 2000 king cab xe with 215X65R15 and i changed them to 31X50R15. just wondering how much that would throw off my milage count and my speed ometer when driving.what about my mpg as well



any responce will be good.
 

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The tire size chart in this link can tell you how your speedometer will be affected. However, checking you mileage yourself is the only way to determine your new mpg.

tire size chart
 

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dflw_99 said:
thx

does anyone else have 31X50R15 on thier frontier
I don't know what that designation means.
Do you mean 31 x 10.5 / 15 ?

Looks like you're going from about 26" to 31".
That's a big difference: around 20% !

That should represent a 20% change in your speed (you'll be reading slower) and a 20% decrease in miles on the odometer.

Theoretically, you've increased your effective gear ratio (lower number: say from 3.73 to 3.00). That should give you poorer performance off the line, but better fuel mileage and a better top end.

Unfortunately, the "real world" observation seems to be poorer performance and poorer fuel mileage (don't forget to take into account your odometer change) and poorer top end. Maybe that's because of the greater rolling mass to overcome, or aerodynamics, or whatever else. I don't understand why it doesn't work that way and I haven't changed tire size significantly enough to have any personal experience.
 

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dflw_99 said:
thx

does anyone else have 31X50R15 on thier frontier
Not a frontier, but I just put a set of 31x10.5x15 Yokohama Geo A/T Plus on my '92 Pathfinder. The tires and a set of new black US Wheel rims really changed the look and feel. They're a little noisier than the Michs I had before and there is a bit more body roll with the taller sidewalls, but the ride is smoother and these tires really sling some mud. The mpgs appear to have gone up by about 2 (was 17-18 now 19.9 on the first fill) after adjusting for the odo variation of 9.05% (determined by highway milemarkers).

All said, I'm pleased, but I doubt these tires will last as long as the previous.
 
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