Another 295 Nitto thread: Revs per mile?

[RTillery]

Has anyone come up with the correct Revs Per Mile on the 295/70/17 Terra Grapplers on stock rims and confirmed it with a GPS?



I need to recalibrate my speedo as I track my mileage and write it off. I do not want to penalize myself with too high a number, and Nitto doesn't list it on their website. The tire calculators I have looked at seem to come out around 608 but if someone could confirm it, it would be a big help. Thanks!

 

[JHardwick]

materials list. .



1. ) piece of chalk

2. ) 100' tape

3. ) 100' of flat concrete or asphalt



most accurate way I know possible

 

[RBischke]

295/70/17 is the same diamiter as 295/75/16. On BF Goodrich web site 295/75/16 TA is 626 rev per mile. Compare 285/75/16, 285/70/17 and 285/65/18 all the same size only the hole in the middle different. The bigger the hole the more they cost.

 

[joaker]

Have not GPS'd it but I have an equation that works and have tested to be accurate on my truck, and calculated out the Revs per mile for this tire according to Nitto's hieght measurement of 33. 19 inches, as 607. 6564 Rev/Mile

 

[RBischke]

On the BF Goodrich chart the 295/75/16 is 33. 2 inches and 626 rev/mile.

 

[PKnoerzer]

I calculated 621 for mine and it checks out with a GPS at les than 1/2mph difference. Odometer error is les than 1%.

 

[EBung]

Have not GPS'd it but I have an equation that works and have tested to be accurate on my truck, and calculated out the Revs per mile for this tire according to Nitto's hieght measurement of 33. 19 inches, as 607. 6564 Rev/Mile

That calculation would be closer to a 315/75/16 tire trust me

 

[RTillery]

Great input, but still no definitive answer. The websites and calculators vary by "twenty sumpin" revs and so are the answers I am getting here. Why such a wide range? PKnoerser seems to have it nailed pretty close if he has GPS'd it. Are you slightly slower or faster on the Odometer?

Thanks Guys

 

[PKnoerzer]

I don't remember whether it was high or low - sorry. It's as close as most new stock vehicles.

Paul

 

[AlexWV]

I used to run 295/75R16 and a good number for those was 626. I am going to say that PKnoerzer's 1% error with 621 is on the low side, meaning if his odo says 100 miles he really will have gone 101 miles. To fix that, he would increase the number from 621 which takes you in the direction of 626. A number like 607 or 608 is going to way off. The correct number for 315s is 601 (verified with GPS).



I have found that numbers given by BFG are very close. For the 295/16, it used to say something different from the 626 that I used and now it says 626 which is perfect for those. For 315s it says 601 which is perfect for those.



Going by that record, I put 634 for 285s which is what BFG says and I am 0. 5% off (low) right now. That is closer than stock where I was 0. 7% off (high).



If I got those Nittos I would put 626 and know that I was very close. Then I'd check it with a GPS.

 

[JHardwick]

Have not GPS'd it but I have an equation that works and have tested to be accurate on my truck, and calculated out the Revs per mile for this tire according to Nitto's hieght measurement of 33. 19 inches, as 607. 6564 Rev/Mile

Care to share your equation?

 

[sag2]

Here is the most accurate way. Using the circumference method below is closer than using tire height, because it gives you the actual distance the tire travels per revolution.

The close way.

If you use Ebung's diameter of 33. 16 and calculate it just using the diameter you get the following. 63360 (inches in mile) divided by 104. 122 ((33. 16 (Tire diameter) times 3. 14 (pi)) you get 608 revs per mile. You should come out close to that using the method below.

The best way.

To get exact revs per mile, mark a spot on the sidewall and the ground, roll the truck until the mark exactly meets the ground again. (I actually use a dab of grease on the tred, then measure the distance between grease spots on the ground. ) Measure the distance between the marks, that is the tire circumference.

Rev per mile is 5,280 times 12= 63,360 inches in a mile.

Divide that by the circumference, and you have exact rev per mile. As the tire wears, you will be off some, so you might want to subtract one or two inches from the circumference to get a mid point of the tire wear.

 

[AlexWV]

I understand the math completely but if you take the published diameter and calculate a number from that you will be well and truly off. 607 - 608 is the wrong number for that tire. If you want to calculate it do what sag2 and others say and measure the circumference by rolling the tire on the truck and seeing how far it goes for some number of turns.



To convince yourself of the wrongness of using 33. 19 as the diameter for your calculation, go out to your truck and measure from the ground to the top of the tire. That measurement on my stock Michelins was about 1" less than the published diameter. On my 285s the published diameter is 32. 8 and I just measured 31. 75.



Now try the math on 33. 19 published diameter for the Nitto less an inch. I came up with 626. 5. Measuring that way is not as accurate as measuring it by rolling the truck but still it should convince you not to use 608 which is going to make your odometer and speedometer read too high.

 

[Ereynolds72]

materials list. .



1. ) piece of chalk

2. ) 100' tape

3. ) 100' of flat concrete or asphalt



most accurate way I know possible

Just running the #s, I came up with 606. 38 rev/mile though this is the best method to determine your actual rolling circumference. The tire is always actually smaller than they "calc. " out to be which would result in more revs/mile.

 

[DF5152]

i hve these tires and i figure they are off by about 3% not worth the trouble to make the change. i checked the speedo against a GPS and found it to be accurate up to about 40mph and off by less than 1-2 mph above that the speedow was a little faster

 

[RTillery]

Does anyone know what the stock revs per mile number for 265's is that is loaded into the ECM from the factory?

 

[RTillery]

Ok, here's the deal. I was coming back from Colorado Springs and stopped in to Medved in Castle Rock. They had quoted me $48 (too much but better than the $108 by another dealer) so I decided to have them set the Revs with the DRB. Truck was back in the shop for maybe 15 minutes.



After much measuring, guessing, reading, input from you fellows, and sticking a wet finger in the air, I had them use 620 revs per mile. It came out just about perfect for what I wanted. At seventy-five mph, I am about

1 to 1 1/2 mph slow (speedo reading slightly fast) checked with my GPS.

I tend to lean on the speed limit and this will give me a slight cushion. I am assuming the odometer will read a like about to the high side which will be to my advantage when I am tracking my travels.



If you wanted it spot on, I would go with 622 or 624 and you would probably be too close to measure. So far, I am liking the Nittos. Quiet, track pretty straight, ride a little softer, and look prretty cool. Can't wait for it to snow, it is 104 degrees today!

Thanks for everybody's help.