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Odomometer readings on 245/70R16
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=8&t=13703		 Page 1 of 1
Author:  Video Guy [ Mon Oct 23, 2006 10:52 am ]
Post subject:  Odomometer readings on 245/70R16
I'm trying to find out how much my mpg has changed since upsizing from 215/75R16's. I have not had my speedometer recalibrated. I've seen the tire calculators on 4lo.com, but I'm not sure how to apply that info to my odometer. According to those calculators, my 245/70R16 turn 684 revs per mile as opposed to the 703 revs/mile for the old tires. When I divide 703 (new) by 684 (old), I get 1.028. Can I assume that for every odomometer mile, I'm actually driving 1.028 miles? If so, I'd multiply the trip odometer reading by 1.028 to get actual trip miles driven.

Is this right :?:
Author:  snowsport [ Mon Oct 23, 2006 11:27 am ]
Post subject: 
That's about it. The difference is very small with that tire size.
Author:  KJMedic [ Mon Oct 23, 2006 2:58 pm ]
Post subject: 
My GPS says that my Speedo is right on with my 245/70/16.
Author:  raceinfan [ Mon Oct 23, 2006 5:06 pm ]
Post subject: 
same here I've clocked mine with one of those Police speed trailer things that tell you how fast your going mine is dead on
Author:  RFCRD [ Mon Oct 23, 2006 5:08 pm ]
Post subject:  Re: Odomometer readings on 245/70R16
Video Guy wrote:
I'm trying to find out how much my mpg has changed since upsizing from 215/75R16's. I have not had my speedometer recalibrated. I've seen the tire calculators on 4lo.com, but I'm not sure how to apply that info to my odometer. According to those calculators, my 245/70R16 turn 684 revs per mile as opposed to the 703 revs/mile for the old tires. When I divide 703 (new) by 684 (old), I get 1.028. Can I assume that for every odomometer mile, I'm actually driving 1.028 miles? If so, I'd multiply the trip odometer reading by 1.028 to get actual trip miles driven.

Is this right :?:

Start by rechecking your rev/mile chart. A typical 245/70/16 should be in the Low 700's (704-706 range), comparable to factory 225/75/16 (711 rev/mile) and close to 215/75/16's (71? rev/mile). Since they are already on the vehicle, try checking your odometer against measured distances on the expressway (10 miles or so) to see how accurate the current settings are. A stopwatch is also helpful, see how long it takes to drive a measured mile when you are holding a steady 60 mph. You may be pleasantly surprised to find this is already fairly accurate.
Author:  labman1 [ Mon Oct 23, 2006 9:21 pm ]
Post subject: 
Once again you all answered my question and I did'nt even have to ask 8)
Author:  Eddo [ Mon Oct 23, 2006 9:40 pm ]
Post subject:  Re: Odomometer readings on 245/70R16
Video Guy wrote:
I'm trying to find out how much my mpg has changed since upsizing from 215/75R16's. I have not had my speedometer recalibrated. I've seen the tire calculators on 4lo.com, but I'm not sure how to apply that info to my odometer. According to those calculators, my 245/70R16 turn 684 revs per mile as opposed to the 703 revs/mile for the old tires. When I divide 703 (new) by 684 (old), I get 1.028. Can I assume that for every odomometer mile, I'm actually driving 1.028 miles? If so, I'd multiply the trip odometer reading by 1.028 to get actual trip miles driven.

Is this right :?:


That's about it. GPS would be the most accurate way to get exact reading for reference. However, remember the speedo/odometer might not have been exact on from the factory. Supposedly some very by as much as 5%.
Author:  gopherbeats [ Mon Oct 23, 2006 10:33 pm ]
Post subject: 
My speedo is 1.7 mph slower compared to my gps value with 245/70/16.
I never did clock it before I got the new tires....
Author:  Video Guy [ Tue Oct 24, 2006 9:43 am ]
Post subject: 
I was the last cell phone holdout on the planet, and now I feel like the only person without either an iPod ( :shock: ) or a GPS unit. On top of work, school, wife, and kids, I don't have time to learn any new gadgets. :?

According to the General site, my diameter is 29.5", 707 revs per mile. My old Wrangler ST was 729 revs per mil and 28.7" diameter. Speedometer/odometer variance is insignificant, which is what I was afraid of. The reduced mpg is a result of the tires, not the speedometer. I find myself filling up with 20-30 fewer miles on the trip odometer. Driving in town and the suburbs, I get about 270 miles every 16 gallons, which is just shy of 17 mpg. It's a small price to pay considering I was only getting 18 mpg with the stock 215's.

Thanks for the feedback, everyone.
Author:  RFCRD [ Tue Oct 24, 2006 11:05 am ]
Post subject: 
Video Guy wrote:
I was the last cell phone holdout on the planet, and now I feel like the only person without either an iPod ( :shock: ) or a GPS unit. On top of work, school, wife, and kids, I don't have time to learn any new gadgets. :?

According to the General site, my diameter is 29.5", 707 revs per mile. My old Wrangler ST was 729 revs per mil and 28.7" diameter. Speedometer/odometer variance is insignificant, which is what I was afraid of. The reduced mpg is a result of the tires, not the speedometer. I find myself filling up with 20-30 fewer miles on the trip odometer. Driving in town and the suburbs, I get about 270 miles every 16 gallons, which is just shy of 17 mpg. It's a small price to pay considering I was only getting 18 mpg with the stock 215's.

Thanks for the feedback, everyone.

Don't feel left out, I don't own a GPS, iPod, or an EVIC. I used my '85 vintage Sharp Business/Financial calculator in my grad. school class. The professor did a double take and guy next to me thought it was an antique. :lol: But it still works.

On your Jeep, the dealer can recalibrate the speedo/odo to the new tire size with their computer toy.
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