speedo recal...??

[XJSuperman]

For those who have had a dealer successfully recalibrate your speedometer after changing tire size...

What was the cost?

and what amount of time did it take them to do it? I need to know if I should schedule it or just go in and get it done on the spot.

 

[Bob4x4]

If you can supply the correct revs per mile it is a simple operation.

Most tires are not the advertised height. When I am allowed enough time I check with a GPS and set it at 60 mph ,at 90 mph it is usually accurate with in 1-2 mph. Good luck finding some one caring enough to do it accurately.



Bob

 

[bighammer]

Some websites list the revs/mi (I know I saw the 315s are supposed to be about 601-- Can't remember if it was BFG or TireRack site)



There were other sizes listed as well.

 

[XJSuperman]

That's what I am getting. . the BFG 315's. I knew they were 601/mile... I did not think about using my GPS though (duh) so thankyou for reminding me on that I can check it to see how far off it is.

 

[KHaeckler]

Speedo

XJ,

My truck just went in for a recall/reflash and the service manager asked if I wanted my speedo calibrated for my 35"'s. When I picked the truck up, it was done and it's right on. No charge. Great service crew at Lithia Dodge in Medford, Oregon.



Karl

 

[GregoryBrooks]

The Medford Lithia Dealership is the Training grounds for Lithia Dealerships Nationwide. The other day I was there I meet a new manager from Oklahoma City doing his internship. Customer service and P. R. is a big thing with the folks there. Thank's for the Speedo info it will come in handy when I go big on tires.

 

[JEly]

I had mine done at the local dealer but I will say if they do it like they were "trained" they will put in 587 for the revs/mile.

That is the number they put in and I was a 1/10 off every 4 miles.

I found on the BFG web site the revs/mile for the 315 were 601 and took that back to the dealer and explained to the tech which I will say was not very happy that I-------a person who hasnt been through their "tech school" would know what they are talking about would be right--------------After some discussion he did put 601 in and it is right on----------------Like he said "The customer is always right"

They did charge me 1/2 hour the first time but it takes all of 5 minutes if that.



JIM

 

[sag2]

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. Measure the distance between the marks, that is the tire circumference.

Rev per mile is 5,280 times 12=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.

 

[bighammer]

Bill Marsh Dodge here in TC wanted one hour labor for a speedo recalibration. I walked out.

 

[JEly]

How the tech did it for me was he measured the tire with a tape which came out to 9'3"... ..... he rounded it out to 9'. He then took 5280 divided by 9 and it was 586. 6 thus the 587.

I double checked his work when I got home

 

[Mundgyver]

Buy yourself one of these Abbott Ratio



http://www.fast-diesel.com/cummins/era.html



and you won't have to worry about what size the tire is. You can run any size you want and do the calibrations yourself.

 

[XJSuperman]

I appreciate all the info. I had the tires mounted this afternoon and after driving on them for a few miles at various sppeds in and out of OD... there is not a big discrepancy. A difference of about 175 RPM is all there is... so before I was right at 2000 RPM at 70 in OD (2041 is more exact) and now it sits at a hair under 1900 (around 1880).



Close enough for me.