So I always assumed that my speedometer was accurate, especially with stock wheels and tires, however I started using the Waze app on my iPhone which displays your current speed, and I noticed that my speedometer consistently reads 3mph faster than my app which is using a GPS and I assume that to be accurate. The app exactly matches the speedometer in my two Subarus also. What's troubling is that if my speedometer is reading fast, my odometer is probably also racking up miles faster than it should diminishing my warranty. Has anybody else experienced this? Is there any way it can be corrected?

 

This discussion comes up every now and again. It is intentional that the speed over estimates by about 2-3 miles per hour. This in no way affects the odometer which is totally separate.

If you dislike it, the over-estimation setting for the digital speedometer can be disabled with NCS Expert.

 

I upsized my tires one size keeping the same aspect ratio and my error went from 2-3mph to 1-2mph. Or you can hack it with NCS

 

Ditto to the above. My speedo was normally about 6% fast compared to the GPS (reading 32 at 30, 55 at 52, 65 at 61). I put 215/45/17's on it this year and cut the error in half, and have no rubbing issues. GPS is now reading 63 when speedo says 65.


I don't mind, it would be a bigger issue if it was reading slow.


Mike

 

Auto manufacturers work within the guidelines of many laws. I understand one is that they 'can not' sell a car with a speedometer indicating less than the actual speed but they can sell one that indicates more than the actual speed by up to 10%. It's not hard to figure out which way they would go.

 

Note the un-corrected speed only shows on the tach speed readout. The dial in the center of the car will still indicate high.

 

A little mental mathematical gymnastics solves the problem. Posted speed limit says 65, set the speed indicator to 71 and you're good to go. You're bookin' 68 and not setting off any alarms. In a 2 hour drive you've saved 6 minutes - woopee!

 

Only the speed is off not the odometer. As said above it is a goofy law that allows for the delta from actual.

And the federal nanny state would prefer we all drive slower. So 65 on the display being 63 makes the nannies feel like they are doing something to make us all safer.

 

I'm running this same tire size and my speedo error is almost cut down to nothing from the 5-6mph difference I had with the stock 15" wheels

 

Are you talking about the giant analogue speedo or the digi one in the tach housing? I never rely on the biggun owing to parallax error.

 

Digital one in the tach housing. The analog gauge is just for show. Too far away to read quickly without taking your eyes off the road.

 

Okay, thanks. Now I'm on the same page. I find the big one is perfect for passengers that want to tell me I'm speeding.

 

^^My daughter likes to tell me that!

 

If you're not going to speed, why buy an MCS? Lol