Hi everyone, I've got a 2010 G37S Sedan. Every time I drive past a radar speed sign, for some reason my speedo reads higher than I'm going according to the radar. This seems to be very consistent with all the radars I've tried. Is it a common issue that the speedo is reading fast? For example, speedo will show 35mph and radar will show 32mph.

Edit: Here is something else to think about. Usually when speedometer is fast, the odometer will follow, however I've used google maps to verify that odometer and trip readings are correct.

 

It's common. Speedo reads about 2-3% faster than radar checked speed. Try this: set your cruise at exactly 70 mph on a straight flat road. After this reset your avg. speed display. Check what reading you get on the display vs the 70 mph on your speedo.

Many cars do this.

 

Police are trying to give you the benefit of common speeding practices

 

I don't think that's the case, because every other car I've had before was pretty accurate based on that reading. This is the first car that's off.

 

Never had a vehicle or been in one that read accurately...must be a conspiracy

 

Because aliens.

 

 

I used a GPS app on my phone to determine the speedo is 7% fast! That's as bad as my Bandit. I noticed everyone passing me when I was driving 5 mph over the limit. They couldn't all be grossly speeding thus the speedo check.

I purchased 255/45-18 for the rear to reduce the speedo error to a mere 5%. Makes the math easier for determining indicated speed to allow a true 5 over. I haven't checked odometer accuracy.

 

mine is optimistic, too. i wonder if the 19" Sport wheels have a different rolling diameter than the 18" wheels? i was thinking maybe its calibrated for 18's, and the 19's throw it off a bit.

if i ever get really bored i'll compare with a tire size calculator ...

 

since i got my g my speedo has shown a lower speed than the actual speed displayed by any gps speedometer app on the phone. the difference is about 10%!! this is on OEM wheels and tyres

all cars i have owned had a 5% speedo error and speedo showed a higher speed than gps app speed on phone

 

Doing ~130 on the motorbike as indicated by the speedo was only ~115 on the gps (this is in mph ). Bikes are notorious for this. My G37 with stock tire sizes has been pretty accurate, within a mph or so, both as indicated by the speedo/radars and several gps devices (phone, garmin).

Some cars can be reflashed for different tire sizes/rear end gears, etc. Not sure if the G falls in this category, but possible something was modified by a previous owner?

 

My came from the showroom with a fibbing speedometer. I was hoping 19s wouldn't be off as much as the stock 18s but I just can't seem to score a set of coupe wheels. Not thrilled with aftermarket choices and prices.

My indicated 160 on the Bandit was only 145 true. Color me disappointed.

 

What's another 15 mph at that speed

 

Mine reads about 2-4 mph over what the speed signs say I'm doing, or when I use the speedo on my phone's GPS. It's weird. Honestly though, I'd rather the speedo read faster than slower.