Scion IA Forum banner
1 - 20 of 24 Posts

·
Registered
Joined
·
204 Posts
Discussion Starter · #1 ·
When I set the cruise, the digital readout says 88 mph when the speedometer reads 90, when I noticed this I tried it at lower speeds and I noticed the same thing- 2 mph difference between the two. I was wondering which was wrong, the speedometer or the cruise control digital readout? I tried the average speed thing and with the cruise set with the digital readout saying 90 mph the average speed after 10 minutes was 89 mph... with the cruise set the whole time and the speedometer reading 92...
 

·
Registered
Joined
·
235 Posts
Hm... that's a real tough one.. don't they both run off of the vehicle speed sensors. Like... the same ones ? I don't get why there would be any difference at all.
 

·
Registered
Joined
·
204 Posts
Discussion Starter · #3 ·
They should run off the same sensors, and probably do, but I think the gauge may be off, like the face isn't on straight, because now that I'm actually looking at it and paying attention it doesn't seem to read 0 when the car isn't moving, more like 1 mph.
 

·
Registered
Joined
·
204 Posts
Discussion Starter · #5 ·
I'll definitely have to find time to take it back down to the dealership... but for now I'll just pay more attention to my radar detector's speedometer than I usually do.
 

·
Registered
Joined
·
235 Posts
Yeaa I would just go with that readout instead. If the rims/tires were changed, it would be the same reading regardless
 

·
Registered
Joined
·
204 Posts
Discussion Starter · #8 ·
The car is bone stock, original rims and tires. I have an appointment at the dealership in 2 weeks.
 

·
Registered
Joined
·
1 Posts
This happens because of european regulations, which require that the speedometer cannot show a speed lower than the actual vehicle speed, even if the customer installs aftermarket wheels and tires. The speedometer therefore reads higher than the actual speed. That said, if the odometer based its readings off of the incorrect speed readings, the car would show higher mileage than it actually has, opening up legal problems from people claiming that the car artificially accelerates the mileage and cheats them out of lease or warranty miles. So the car has to keep track of two speeds - the fake speedometer speed and the real vehicle speed. Usually, the cruise control display agrees with the fake speed, but the "average speed" function in the trip computer is tied to the actual vehicle speed so that fuel economy calculations, etc., are more accurate. It sounds like either the iA or your particular car is confused about which is which.
 

·
Registered
Joined
·
24 Posts
This is very normal. Every car I've ever driven is off by 1 or 2, sometimes as much as 5 miles per hour.
 

·
Registered
Joined
·
204 Posts
Discussion Starter · #12 ·
1 or 2 I wouldn't really care for. But 5mph could be the difference in a ticket lol
Depending on which way off the speedometer is, 1 or 2 could mean a ticket! I'm not sure how y'all drive, but I stay at 9 over (cops don't really care about speed, but state troopers will get you for 10 or over) and if the speedometer read 64 but I was doing 65 I could get a ticket. In a new car, the speedometer should read correctly, and if it doesn't it should be fixed for free. It's fine with this though because it's how it's supposed to be, but I know that with my LTD the speedometer was supposed to read correctly, but it didn't, so I went and had the cable replaced because it was worn out. I just go by my gps now, its more accurate anyways.
 

·
Registered
Joined
·
330 Posts
Depending on which way off the speedometer is, 1 or 2 could mean a ticket! I'm not sure how y'all drive, but I stay at 9 over (cops don't really care about speed, but state troopers will get you for 10 or over) and if the speedometer read 64 but I was doing 65 I could get a ticket. In a new car, the speedometer should read correctly, and if it doesn't it should be fixed for free. It's fine with this though because it's how it's supposed to be, but I know that with my LTD the speedometer was supposed to read correctly, but it didn't, so I went and had the cable replaced because it was worn out. I just go by my gps now, its more accurate anyways.
Get larger radius tires to compensate for speed
 

·
Registered
Joined
·
7 Posts
Been over a year on this thread, but I thought I'd add my two cents anyway.

The analog speedometer reads 2-3 mph more than the cruise control speed. My GPS agrees with the cruise control readout. I believe the cruise control speed is actually from GPS. The car must have GPS, otherwise how would the compass and altimeter work?
 

·
Registered
Joined
·
102 Posts
Been over a year on this thread, but I thought I'd add my two cents anyway.

The analog speedometer reads 2-3 mph more than the cruise control speed. My GPS agrees with the cruise control readout. I believe the cruise control speed is actually from GPS. The car must have GPS, otherwise how would the compass and altimeter work?
I have the same problem with my ia.. but it's one 1 mph more than what cruise control shows..

It's annoying but not a big deal..
 

·
Registered
Joined
·
9 Posts
I see that in my iA too (speedo shows 2 MPH higher than cruise control setting) but I thought it was just trying to stay a bit above the set speed to allow for up hill travel. I got it used but looks to be all stock.
 

·
Registered
Joined
·
97 Posts
WilsonT123 - I'm looking to buy a 2016 Scion iA 6-speed stick in the Pulse color for $13,334. It's only got 28,526 miles on it. Looks absolutely cherry. It's about 162 miles west of me over a snowy mountain pass, however.
 

·
Registered
Joined
·
102 Posts
Mike, where in the world are you cruising at 88 - 90 mph.. Damm..... My speedometer is off by 1... If I'm going 60, its showing 61... Probably the same for you... Its more annoying than anything...

No help, just comment...

When I set the cruise, the digital readout says 88 mph when the speedometer reads 90, when I noticed this I tried it at lower speeds and I noticed the same thing- 2 mph difference between the two. I was wondering which was wrong, the speedometer or the cruise control digital readout? I tried the average speed thing and with the cruise set with the digital readout saying 90 mph the average speed after 10 minutes was 89 mph... with the cruise set the whole time and the speedometer reading 92...
 

·
Registered
Joined
·
46 Posts
My gauge reads 2 mph faster than the cruise control speed. Not a big deal really. This has to be factory because reading all the other comments we all have the same "problem". I wish we had the Mazda 3 cluster, it's SO much better. I wonder why Mazda didn't install these in our cars... Oh well.
 

Attachments

1 - 20 of 24 Posts
Top