Speedometer is off

[MorttheMazda]

My speedo is f***ed! In the lower speeds, it's fine, but once i get up to about 45 km/h it starts showing i'm going faster than i really am. It says I'm going 100km/h, but i'm really going 89km/h. I've searched it and I've got two answers. One is saying there is a speed sensor in the rear wheel, but i can't seem to find it. The second says it's in the engine bay near the transmission. I don't have any codes being thrown and the wheels I have on are 17" with low profiles. I've checked the comparison between stock size and my size and it's damn near the same. It should only make the speedo be off by 4-5km/h at higher speeds.

Can someone help me out and possibly give me an answer/fix?

I have a 2006 2.3L Manual with 205/40R17 tires
Thanks a lot!

 

[brandini]

That isn't the stock tire size is it?

 

[brandini]

You have the wrong tires, fix that can the error will be less, but still not perfect as it should tell you you're going a tad faster than actual.

 

[MorttheMazda]

The same thing happens when I put my snow tires on though, which are 195/55R16. It's off by the exact same amount

 

[brandini]

Then you're within the margin of error for whatever you're reading your 'actual' speed with. Your snow tire is halfway between stock and your current tire size as far as accuracy-to-stock is concerned.

Tire pressure, wear, alignment can all affect speed readings.

Our speedo isn't that accurate anyway and varies in accuracy throughout the range even on stock wheels and tires like I am on. You're just making the (small) issue worse.

And now that you know, just add 5-10%to your desired speed and 'make it so' on your speedo.

 

[MorttheMazda]

Alrighty then! Thanks guys