[albertlastsmart]

I am putting 15x5.5 rear wheels with 175/55/15 tires,on all 4 corners.Does the speedo/odo get it's speed/mile readings
from the front,or rear wheels?? If from the front wheels,will the larger tires change the readings?? What change/error,
expressed as decimal + or- ?? (to compute MPG).................

 

[Mike T]

It averages from all 4 and it should be OK since that is a standard size.

 

[InjuredAgain]

It averages from all four? That's really unusual, and typically the speedometer is driven by the front wheels.

 

[Mike T]

It uses the speeds computed by the reluctor rings on all 4 wheels to determine vehicle speed.

 

[otbiker]

our MB Sprinter motor home does the same thing. Guess that's just how MB chooses to do it. Was going to install a speedo-healer, but then...

 

[albertlastsmart]

I have noticed..................

that with the OEM 165front/175rear,that the speedo was 5MPH slower,compared to GPS. So I to assume there is also a
"shortage"in the miles showing in the odometer?? Anyone else notice that?? If there is a"shortage"in the odo,what decimal
percentage to get accurate mileage??..................

 

[MB DNA]

So I to assume there is also a "shortage"in the miles showing in the odometer?? Anyone else notice that?? If there is a"shortage"in the odo,what decimal percentage to get accurate mileage??..................

Speedometer/Odometer have different sources.

smart speedo is fast, odometer is accurate.

May want to do a search for some lengthy debates previously posted on the subject?

Here's a start...

http://www.smartcarofamerica.com/fo...curacy-vs-odometer-accuracy-46619/index2.html

http://www.smartcarofamerica.com/forums/f353/5mph-difference-actual-mph-44366/

http://www.smartcarofamerica.com/forums/f4/speedometer-error-5160/?highlight=speedometer+error

http://www.smartcarofamerica.com/fo...eter-errors-9756/?highlight=speedometer+error