So the wife and I were watching a report on the news about Honda having faulty speedometers in most of their new vehicles which read exactly 2 miles per hour fast. They were sued for it and had to make alot of changes and recalls. Well I installed GPS in my rubi and funny enough the factory speedo always reads EXACTLY 2 mph fast. Im not sure how accurate the GPS is but it uses 11 Satellites and no matter what speed I try and match (cruise control on) it never matches? Does Jeep adjust the factory speedo for the rubi tires? Can anyone else (maybe with a rubi) with a GPS verify this?

 

I did the same test when I read that story and mine is dead on with original tires.

 

Checked with GPS, mine was dead on with the factory tires, 225/75/16's in my case. Of course, now they are 8% off with 265/75/16's.

 

ON BOTH OF MY 03 RUBICONS
MY SPEEDO WAS DEAD ON WITH 35'S ON THEM WITH NO CALIBRATIONS.

 

Mine reads fast too, GPS says 68, speedo says 70.

 

i haven't checked my 07 yet, but my 97 TJ read 5% slower than i was going (i think)

i passed one of those community radar boards. Not sure if they are used in the states, but they are unmanned and placed along local roads (usually at the request of people in the neighbourhood) They simply display your speed, tell you what the speed limit is, and ask you to slow down (if you are going too fast)

anyway, that device indicated a difference of 5 km/h (my speedo read 63, but the board said 58)

a guy I work with had an intrepid in the late 90's, and he drove on the highway with a friend and compared speedo readings. the intrepid was also 5% slower than the speedo read.

looks like it might be a common occurence for chrysler.

 

I have had CJ, 3 TJ's and now the Jk. I don't think any of them were spot on. Now my Jk with 33's is right on with my GPS.

 

I read something either in Road and Track or Car and Driver or one of the gazillion car magazines that I subrcibe to that the majority of cars were off by at least 1 mph, either too fast or too slow. I dont remember the exact percentages but I think they said something like 10 to 20 percent were off by 3-5 MPH. This was several years ago that I read this so it might not be accurate anymore, but I thought it was interesting.

 

I recall reading that same article (it was Car & Driver), and also thought that it was interesting.

As long as the speedos are 2 mph off in the correct direction (i.e. they say you're going faster than you actually are) I don't see it as much of an issue. I haven't checked mine yet with GPS, or police radar board, but I'm not concerned in the least.

 

If it says 60 MPH on the Speedo when going 58...doesn't that also mean you only have gone 58 miles when the Odometer says 60?? ... so then if your Odometer says 100,000, you have really only gone 96,666 miles or @ 3.4 % off?