MPH. help
 

hello to all
when i got my x5 last year,it came with p225-65-r17 tires tag on door calls for 235-65-r17 according to sites at 60mph it should be 61 no big deal my issue is no matter what gps i use in this vehicle it reads that i'm 10.mph off.so 60 it's really 50 but when i use the same gps on my other vehicle they are on point.
what other test can i do or my speedo really off.??? thanks

The sidewall of a 225-65 is smaller then a 235-65.

Smaller tires will need to rotate more per mile when new, even more when worn.

Oh, I misread the post.

Yeah, time for a speedo recalibration.

^ What trader4 wrote...
the diff on 225 vs 235 in OP's size is nominal.

And, Ibid on the interstate mile marker with stopwatch test. Do it a few times, steady on the speed.

Not sure I agree that most GPS units are spot on, in terms of speed.
GL, mD

Will you be using the OBC's built in STOPWATCH? Ifyes, Iwonder if they work in cohoots with one another....BMW's built-in way to protectyou from getting speeding tickets. :D (I kid)


Just in case someone didn't know...the high cluster/high MID (and Nav screen) has a STOPWATCH feature...and you can see the symbol (far right on MID display in pic below) when it is initiated:

my instrument cluster also has a digital readout of your speed, you just got to unlock it by adding the last 4 of you vin and putting that number into the unlock test

Unlocking cluster requires the sum of the last 5 digits of your VIN. :) Then go to OBC TEST #8 to see momentary road speed (in kilometers). :)

Your GPS is telling you that the tires are too small. Way too small.

You can (I do) run a 245/65x17, and the speedo will be much tighter on reality.

Your GPS is right to within a few feet on location, and it's only wrong because the original military applications that went to civilian use were required to have an error in both time and space.

If you get bigger tires, 245/65x17, then the tires turn slower for the same speed, or more speed comes from the same speedo reading.

Bottom line, the 225s are too small. Do not buy them again.