EXCLAIMER: This is an exercise to show one effect of changing wheels. There are Other factors, but this is assuming everything else is equal. (theoretical, I don't have every number to calculate the difference in rolling resistance, drag on the driveline, tire traction, changing weight of the vehicle, altitude, weather, number of ducks.
I was playing around with the Tire calculator today and noticed the difference in tire revolutions per mile. Since I'm planning a trip, I was wondering if my calculations were going to be off due to that difference, and if so, how this effected the budget. So I thought I'd make a write up about it, because it's one thing people don't think about when getting new tires.
To start with, using Tire size calculator and entering the factory tire size for my 1gb AWD-205/55R16 and I get 811 revolutions per mile. Then I enter my current tire size, 205/50R16 and get 838 Revs per mile. I was thinking of my Evo wheels and if I get 235/45R17 I get 796 revs per mile.
I'll use a planned trip of 1000 miles and show what the odometer would read.
So, to start, we multiply Revolutions Per Mile (RpMi) times total miles. This will be the baseline for comparison, to find out what the odometer would read if we made the trip on different tires.
811 x 1000 = 811000 RpMi.
We take this number and divide it by what my undersized tire RpMi.
811000 / 838 = 967.780429594
The trip odometer would be reading at 1000 miles, but you're not there just yet. You've only gone 967.8 miles. We still need to go to a 1000 miles, so, we find the difference;
1000 - 967.780429594 = 32.219570406 and add that to the 1000 miles the Odometer already reads,
32.219570406 + 1000 = 1032.2 is what your odometer reads for what we know is a 1000 mile trip.
What about the Evo wheels? Do the same math as above, but with the evo size.
811000 / 796 = 1018.844221106. That's over the required 1000 miles. So we'll get the difference.
1018.844221106 - 1000 = 18.844221106
And take that away from the 1000 to see what the odometer would read.
1000 - 18.844221106 = 981.1 miles on your trip odometer for what we know is a 1000 mile trip.
(Evo)0981.1 (Stock)1000.0 (Undersize)1032.2 To find the range, you take the lowest from the highest.
1032.2 - 981.1 = 54.1 mile difference on the same trip.
So you see the difference the odometer readings for traveling the same distance. How is this important? Well, when trying to figure out how much fuel will cost, ya need to know how far you actually go. Lets plan for the 1000 mile trip using the above numbers, and assuming you average 25mpg. And the gas cost $3 a gallon for our favorite fuel.
Starting with the stock, we divide the odometer readings by mpg.
1000 / 25 = 40 gallons. Well, this is how much gas, but how much will it cost?
40 x 3 = $120 So planning to pay for the gas on factory sized tires will be $120 bucks.
Let's try with my tires now. We know what the odometer would be reading if we traveled the trip, So we divide 1032.2 with the same fuel milage.
1032.2 / 25 = 41.288 Gallons. Now for the cost.
41.288 x 3 = $123.86 Hmm, to go the same distance, you spend $3.86 more for the trip. A soda and bag of chips.
Well, what about if I used the Evo wheels?
981.1 / 25 = 39.244 Gallons. So we gotta see how much the total cost is.
39.244 x 3 = $117.73 Hmmm, and doing a quick subraction,
$120 - $117.73 = $2.27 cheaper to use the evo wheels. And if you take $123.86 and subtract the $117.73, you can see a $6.13 difference in cost for the trip.
Okay, so it doesn't look that bad. A meal at Mcdonalds difference between them. Remember the trip I said I was planning earlier? Well, we'll use my trip and my current fuel milage. The numbers won't be as pretty, but it will show a real world example.
3652 mile round trip. $3.099 per gallon for 91, and 29 mpg. (Yes, I drive like I have some sense.
)
STOCK
811 x 3652 = 2961772 Revolutions per Miles. (RpMi)
3652 / 29 = 125.931034483 Gallons
125.931 x 3.099 = 390.260275862 $390.26 for the trip.
UNDERSIZE
2961772 / 838 = 3534.334128878
3652 - 3534.334128878 117.665871122
3652 + 117.665871122 = 3769.665871122
3769.665871122 / 29 = 129.988478315 (Rounded up cause fuel is measured in thousandths)
129.988 x 3.099 402.834294297 $402.83 for the trip.
EVO
2961772 / 796 = 3720.819095477
3720.819095477 - 3652 = 68.819095477
3652 - 68.819095477 = 3583.180904523
3583.180904523 / 29 = 123.557962225
123.558 x 3.099 = 382.906242 $382.91 for the trip.
402.83 - 390.26 = 12.57
390.26 - 382.91 = 7.35
402.83 - 382.91 = 19.92
SO you can see, for a 3652 mile trip, the difference is about 20 bucks at 29mpg. Boosting and getting 18 mpg:
Undersize $402.83 to $649.01
Stock $390.26 to $628.75
Evo $382.91 to $616.90
It's alot of math, but it's interesting to see the effects of tires on your fuel effeciency.
I was playing around with the Tire calculator today and noticed the difference in tire revolutions per mile. Since I'm planning a trip, I was wondering if my calculations were going to be off due to that difference, and if so, how this effected the budget. So I thought I'd make a write up about it, because it's one thing people don't think about when getting new tires.
To start with, using Tire size calculator and entering the factory tire size for my 1gb AWD-205/55R16 and I get 811 revolutions per mile. Then I enter my current tire size, 205/50R16 and get 838 Revs per mile. I was thinking of my Evo wheels and if I get 235/45R17 I get 796 revs per mile.
I'll use a planned trip of 1000 miles and show what the odometer would read.
So, to start, we multiply Revolutions Per Mile (RpMi) times total miles. This will be the baseline for comparison, to find out what the odometer would read if we made the trip on different tires.
811 x 1000 = 811000 RpMi.
We take this number and divide it by what my undersized tire RpMi.
811000 / 838 = 967.780429594
The trip odometer would be reading at 1000 miles, but you're not there just yet. You've only gone 967.8 miles. We still need to go to a 1000 miles, so, we find the difference;
1000 - 967.780429594 = 32.219570406 and add that to the 1000 miles the Odometer already reads,
32.219570406 + 1000 = 1032.2 is what your odometer reads for what we know is a 1000 mile trip.
What about the Evo wheels? Do the same math as above, but with the evo size.
811000 / 796 = 1018.844221106. That's over the required 1000 miles. So we'll get the difference.
1018.844221106 - 1000 = 18.844221106
And take that away from the 1000 to see what the odometer would read.
1000 - 18.844221106 = 981.1 miles on your trip odometer for what we know is a 1000 mile trip.
(Evo)0981.1 (Stock)1000.0 (Undersize)1032.2 To find the range, you take the lowest from the highest.
1032.2 - 981.1 = 54.1 mile difference on the same trip.
So you see the difference the odometer readings for traveling the same distance. How is this important? Well, when trying to figure out how much fuel will cost, ya need to know how far you actually go. Lets plan for the 1000 mile trip using the above numbers, and assuming you average 25mpg. And the gas cost $3 a gallon for our favorite fuel.
Starting with the stock, we divide the odometer readings by mpg.
1000 / 25 = 40 gallons. Well, this is how much gas, but how much will it cost?
40 x 3 = $120 So planning to pay for the gas on factory sized tires will be $120 bucks.
Let's try with my tires now. We know what the odometer would be reading if we traveled the trip, So we divide 1032.2 with the same fuel milage.
1032.2 / 25 = 41.288 Gallons. Now for the cost.
41.288 x 3 = $123.86 Hmm, to go the same distance, you spend $3.86 more for the trip. A soda and bag of chips.
Well, what about if I used the Evo wheels?
981.1 / 25 = 39.244 Gallons. So we gotta see how much the total cost is.
39.244 x 3 = $117.73 Hmmm, and doing a quick subraction,
$120 - $117.73 = $2.27 cheaper to use the evo wheels. And if you take $123.86 and subtract the $117.73, you can see a $6.13 difference in cost for the trip.
Okay, so it doesn't look that bad. A meal at Mcdonalds difference between them. Remember the trip I said I was planning earlier? Well, we'll use my trip and my current fuel milage. The numbers won't be as pretty, but it will show a real world example.
3652 mile round trip. $3.099 per gallon for 91, and 29 mpg. (Yes, I drive like I have some sense.
)STOCK
811 x 3652 = 2961772 Revolutions per Miles. (RpMi)
3652 / 29 = 125.931034483 Gallons
125.931 x 3.099 = 390.260275862 $390.26 for the trip.
UNDERSIZE
2961772 / 838 = 3534.334128878
3652 - 3534.334128878 117.665871122
3652 + 117.665871122 = 3769.665871122
3769.665871122 / 29 = 129.988478315 (Rounded up cause fuel is measured in thousandths)
129.988 x 3.099 402.834294297 $402.83 for the trip.
EVO
2961772 / 796 = 3720.819095477
3720.819095477 - 3652 = 68.819095477
3652 - 68.819095477 = 3583.180904523
3583.180904523 / 29 = 123.557962225
123.558 x 3.099 = 382.906242 $382.91 for the trip.
402.83 - 390.26 = 12.57
390.26 - 382.91 = 7.35
402.83 - 382.91 = 19.92
SO you can see, for a 3652 mile trip, the difference is about 20 bucks at 29mpg. Boosting and getting 18 mpg:
Undersize $402.83 to $649.01
Stock $390.26 to $628.75
Evo $382.91 to $616.90
It's alot of math, but it's interesting to see the effects of tires on your fuel effeciency.
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