CX-5 Speedo error

[ColtX-5]

My speedo has always read low vs GPS. Since I changed to the 19 inch GT wheels its a little worse, 2 mph. It may have gotten me a ticket, recently. Can the ECU be reflashed to compensate for the GT tires?

 

[cz5gt]

did you put oem size for the 19" tires?
As far as I know there is no easy way to change the computer to match the tires.
Mine is also 1 mph difference and thats with the factory 19.

 

[Conrad 16.5]

My speedo has always read low vs GPS. Since I changed to the 19 inch GT wheels its a little worse, 2 mph. It may have gotten me a ticket, recently. Can the ECU be reflashed to compensate for the GT tires?

You got a ticket for 2 mph over?

 

[CarpeDiem]

My analog speedo reads one mph higher than calibrated radar at 55 mph. The digital readout in cruise control is right on. GPS is not that accurate IME compared to a calibrated radar.

 

[Jack Rabbit]

My speedo has always read low vs GPS. Since I changed to the 19 inch GT wheels its a little worse, 2 mph. It may have gotten me a ticket, recently. Can the ECU be reflashed to compensate for the GT tires?

If it was in a 25 mph school zone then pay the fine. otherwise fight the ticket for 2 mph difference. Those radars although calibrated could be slightly off, likewise you can't be responsible if your cars is slightly off.
2 mph will probably get thrown out of court.

 

[cz5gt]

around 3% error. Thats why they set the radar alert at least 5mph over the limit. Often times 10 mph.

 

[Jack Rabbit]

around 3% error. Thats why they set the radar alert at least 5mph over the limit. Often times 10 mph.

Aaaah. Learned something new.

Guess they gotcha.

 

[MzdCX_5]

Yes by using Forscan, visit mazda3revolution 2014-2018 "Change configuration (explore different functions ASbuilt" ,find SergSlim post and at his signature download his Excel file to perform calculation. Read some of Dec-Jan posts they are related to this subject.

 

[ColtX-5]

You got a ticket for 2 mph over?

No, I got a ticket for 85 on an interstate. But the cruise was set to 83 and had the real speed been a more typical 81 or 82, I might not have gotten it.

 

[ColtX-5]

around 3% error. Thats why they set the radar alert at least 5mph over the limit. Often times 10 mph.

The new 19” Wildpeak tires are only 1% larger than the OEM 17" tires. With common error of 2 to 3% high, I would be golden.

 

[cz5gt]

are they 225 55 19?

yes. If the speed limit is 75 then with 3% margin they would usually set the radar at least on 80 mph or more. I have seen tickets for 5 mph over in small counties/towns as they know you would not get back to go to their court to contest it.

With that said, there seems to be option to compesate the diff between speedo and gps with the details provided above but its a bit more involving task from what I saw.

 

[Conrad 16.5]

No, I got a ticket for 85 on an interstate. But the cruise was set to 83 and had the real speed been a more typical 81 or 82, I might not have gotten it.

You were driving 85, while you thought you were driving 83? What was the posted limit?

 

[Oleman]

No, I got a ticket for 85 on an interstate. But the cruise was set to 83 and had the real speed been a more typical 81 or 82, I might not have gotten it.

LOL what did you expect? Next time set it at 73 you'll have many less expensive driving days!