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| Speedometer/Odometer issues. http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=66761 |
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| Author: | ChooChooman74 [ Sat May 05, 2012 8:50 pm ] |
| Post subject: | Speedometer/Odometer issues. |
I am still new here after picking up my CRD last Friday. Right away I felt the speedometer was not accurate. I opened Torque on my phone and checked my GPS speed. Sure enough, 65 on the speedo was 62 on the GPS. That is a difference of approx +5%. I checked my tires online and it appears to be stock 225 75 16 tires. Now today was my first long distance trip. I wanted to double check the accuracy of my speedo. I figure that I would reset my trip odometer and drive a long distance on the highway. I drove 40 miles (using mile markers) and expected to see about 42 miles on the odometer. Was I shocked when I saw 36.5 miles. A difference of approx -9.5%. A 2nd shorter test confirmed this result. What would cause the speedometer and odometer to be inaccurate in totally opposite directions? Is this fixable? Sent from my DROID BIONIC using Tapatalk 2 |
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| Author: | DOC4444 [ Sat May 05, 2012 10:53 pm ] |
| Post subject: | Re: Speedometer/Odometer issues. |
It is just the way they are. DOC |
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| Author: | papaindigo [ Sun May 06, 2012 9:38 am ] |
| Post subject: | Re: Speedometer/Odometer issues. |
I'm not totally convinced GPS accurately measures speed or distance over ground by taking into account changes in altitude or direction (e.g. hills and curves) at least my old boat GPS clearly did not account for curves but then it was slow on updating in real time. Newer GPS do a real time speed so checking your GPS speed vs speedometer is probably accurate. In my case they are almost identical but in my son's case IIRC the difference is 2-3 mph but I forget the direction of the difference. Also IIRC 5%+- is within tolerance limits. The odometer is apparently feed by a different data source and can be off in an independent direction. I would definitely not rely on mile post markers for accuracy. If you want to check odometer accuracy I'd do as staight and level a run as possible for 30-50 miles using the GPS for distance vs odometer and see what you get. IIRC anyone with the fancy DRBII tool can adjust both those reading at least somewhat. If not then know what the difference is and live with it. My mpg calculator has the correction factor built into its formula. |
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| Author: | Dave01 [ Tue May 08, 2012 9:10 am ] |
| Post subject: | Re: Speedometer/Odometer issues. |
I live with it, not a big deal for me. The speedo reads 5% high, the odometer reads 5% low. I ran enough tests to be pretty confident of those numbers, also have the stock size 225/75-16's. It is a shock when you first realize it, when I first drove the Liberty I just assumed they would read from the same sensor. Like you, I asked some questions here to figure it out. The good news is people that don't know it and check their mileage from the odometer get a good surprise when they figure it out, they actually are getting more than 1 mpg higher than they thought. |
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| Author: | tjkj2002 [ Tue May 08, 2012 10:04 am ] |
| Post subject: | Re: Speedometer/Odometer issues. |
OEM speedo's can be +/- 5%,that is the industry standard.For police packages the speedo's have to be dead on a calibrated,will have a calibrated sticker also and must be re-calibrated often.I do not know of any policy or such for acurrate odometers,or a range for them to be in. |
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