revs per mile

[Metalaram]

i checked prior threads on this topic and most had very different numbers also most were from a year ago or more. anyway do any of you know the revs per mile for a 35 12. 50 17 (same as 315 70 17) also i have herd some say the dealers can and some say they can do it. the one near me says they can for 100. 00 and it will take an hour. lastly i heard that they can only do certain sizes and cant go as low of a # as i need. any info would help..... thanks... chris

 

[EEdmondson]

Try http://www.csgnetwork.com/multirpmcalc.html

 

[Metalaram]

that site will give me rpm per mile per hour but not tire revs per mile so they can program the computer

 

[XJSuperman]

No... a 35X12. 50X17 will not produce the same revs per mile as the 315/70's will.



The 35's are about a quarter inch or so larger in diameter and about 5-10 revs LES per mile... and that will even vary between tire manufacturer.





If memory serves the computer can't be set for lower than 540 revs per miles BUT you;d have to have about a 40" tire to make them that low.



The 315 BFGS are set at 601 revs per mile and I believe a BFG 35 is set at 594 revs per mile... BUT again each manufacturer will be slightly different and even a 10th of an inch in diameter results in a slightly different rev/mile for the tire.



You MUST get the revs per mile from your tires' manufacturer to be sure you have it right. Most tire makers have this info available on their websights.



I got raped at paying $70 to have mine done on my last truck so you are getting it even worse if they charge you $100. And it does not take an hour... more like 20-30 minutes and even that's higher than it should take.

 

[EEdmondson]

Check bf goodrich spec page. 315 70RX17 AT KO is 601 revs per mile.

 

[Patriot_RAM]

My dealer reprogrammed mine for my 315's. Took them about three minutes and they didn't charge me. On the contrary, if the only option is to pay the $100, you can get a unit that will do it for you for about $150. I forget the name, but it's been talked about on here before.

 

[krz4elk]

My dealer also did it for free, and it only takes a minute. Don't let them rip you off. If they want your business, they should do it for free, it's quick and easy.



Mike

 

[klenger]

This gear speed calculator may help to compute revs per mile



http://www.klenger.net/dodge/general-reference/gear-speed-calculator.xls

 

[Moterhead]

Here are links to a couple of tire size calculators.



http://www.csgnetwork.com/tireinfo4calc.html



http://www.powerdog.com/tiresize.cgi



The first one is a bit easier to use and gives more info. At the bottom of the tire calculator page are links to many different type of caluculators. Interesting.

 

[Kimber]

here's the one I like to play with... . http://pw1.netcom.com/~sgalaba/tiresize.htm

 

[Metalaram]

well none of the charts would let me figure it out (everything else but) so i got a guy at mickey thompson with a brain as oposed to the bevis and butt head i got yesterday and he said 594. 2 per mile and thats right in there with what most have said (601) for the 315 bfg a/t now i am trying to guess a number of revs to take off to get an average over the life of the tire the F/Cs have 18/32 tread depth in the center (thoughts anyone????) also i called another dealer and they will charge me 41. 99 (much better) and it will be only a half an hour to get done i guess the other dealer like so many of them wanted to get a closer relationship with my back side anyway any of you that are in the market for new rubber should check out the cepek F/C 2s so far i am very happy with them and i have always been a bfg A/T guy. and thanks XJsuperman you nailed it right on and thanks to you i called the other dealer and will have an extra 58 bucks in my pocket!!!

 

[dhill]

Well I guess you could figure it out yourself by measuring from the ground to the center of the axle and using that as a radius. ( radius X 2=D, D X 3. 1416=C,

C/12= C in ft. divide that into 5280 should give rev per mile. Right? Then you could subtract 0. 28125 (half of the 18/32") and do all the calcs. again to find out what it would be when your tires are ready to be replaced. ) However the front tires will have more weight on them than the back, so with the same air pressure the front should make more revs in a mile than the rear. Mabe that's why there two different axle ratios in our 4X4s



Dave

 

[XJSuperman]

dhill... why? If he is rotating his tires every few thousand miles as he should... all the calcualtions in the world will not work as the front /rear tires will be switched back and forth at least 3-4 times over the life of the tires. Thus the reason for rotating them. And where do you get a difference in gear ratios front to rear? At the most you're looking at 4. 11 front and 4. 10 rear... not enough of a difference to do anything... and the 3. 73 trucks wouldn't be any different either. It would take over 100,000 miles to make any significant difference and no set of D rated 35's is going to make it that many miles.





Cgarling. . glad you got it sorted out. The 35's should look nice on the truck

 

[PatrickCampbell]

To convert tire size to inches based on the tire sizewall you would do like this:



265/70/17



265/25. 4001 (mm per inch) = 10. 433 * . 70 (aspect ratio) = 7. 3031 * 2 (since it's a wheel not a half wheel) + 17" (size of rim) = 31. 606"



Now let's take the Revs per mile of of a Michelin LTX A/s 265/70/17 mounted on an 8" wide rim... it is 657 ,this # is given by the manufacturer.



5280 (ft per mile) / 657 = 8. 0365 * 12" per ft = 96. 438 / PI 3. 1415925 = 30. 697"



A difference of . 909"



So... If you don't go by the Revs per mile of your actual tire mounted to your actual width (and height of course) rim, you are going to get a bad number that will be inaccurate.



With a 48RE At 2000 RPM you're off by about 2 MPH... . between the 2 tire sizes.



By the way, you are LUCKY to find a dealer to do it for free. Dealers tried to charge me 1 & 2 hours to do it I kept going until I found a dealer to do it for . 5 hours.

 

[sag2]

To get the exact revs per mile for your tires, have truck sitting straight ahead, put a dab of grease on the tire tread. Roll ahead until the grease spot hits the ground twice. Measure the distance in inches between the spots (center to center), divide 63,360 (inches in a mile) by the distance between spots, and that is revs per mile. Rather than hoping the tire maker specs are correct, this gives the exact number.

 

[XJSuperman]

Boy some of you guys sure know how to make things complicated. Ya'll must work for the government!

 

[thejeepdude]

Boy some of you guys sure know how to make things complicated. Ya'll must work for the government!

The right way isn't always the easy way.



I second the grease idea, except I use a dab of paint... a heavy line of chalk works ok on a smooth floor too.

 

[BRuppel]

Boy some of you guys sure know how to make things complicated. Ya'll must work for the government!

really! especially when you can go on almost any tire manufactures website and it will tell you there. i posted in a different thread the directions on how to change your tire size with the DRBIII just like the dealer would do. tell them it is only 11 steps and should not cost more than $0

 

[XJSuperman]

The right way isn't always the easy way.



I second the grease idea, except I use a dab of paint... a heavy line of chalk works ok on a smooth floor too.

How is it the right way when as I have stated and BRuppel just did also... the TIRE MANUFACTURER has the information needed. A simple phone call or visit to the tire manf. website will be all that is needed.

 

[thejeepdude]

How is it the right way when as I have stated and BRuppel just did also... the TIRE MANUFACTURER has the information needed. A simple phone call or visit to the tire manf. website will be all that is needed.

Have you verified the tire manufacturer's specs? They also say their tires shouldn't need more than 4oz of weight to balance, yet I've seen this happen. Also, do they rate the revs per mile at the average diameter of the tire over it's lifespan, or at it's max diameter when new? If you have free access to a DRBIII or your own calibrator, then you might as well check the diameter again later. Granted, it won't make a whole lot of difference, and maybe none, since they don't allow a decimal number like 601. 3 revs/mi in the computer. But for 2 minutes of my time, I'll do it the same way I always have and KNOW it's accurate. For those of you too lazy ( <--edit: this is a joke) to do the grease/paint trick, I'm sure the manufacturer's provided specs are close enough. Hey, part of the great thing about the TDR is that with input from so many people you can learn multiple ways to do the same thing and then make that decision yourself.