speed test

[Strider]

Hey guys, I have a 94 that has 15" ties. My speedometer says I'm going 75 but on my phone app it says I'm going 70. Isn't the stock wheels on that 15"? Any ideas on why it's off by 5mph?

[Sharpie]

15's were not stock in 94'.

[jrj512]

I think they're all off by at least 5 MPH. Mine is too, even on stock wheels.

[Yeller90]

1+ I have an optimistic speedometer as well

[Flyin96M]

Mine is off about 5mph as well but not until 85 and that is with 225/45/15's.

[chriscar]

What tire size are you running? Not wheel size.... tire size. The stock size is 185/90-14, proper +1 sizing would be 195/50-15. Anything different is going to throw your speedo off.

This site will show the effect of various tire sizes.
http://marksink.com/tire_wheel_offset/tires.html

C

[flyin94m]

As chriscar pointed out, I have 195/50-15's on my 91 and see the same discrepancy. It's less 'off' at slower speeds and diverges as I go faster... It's a time machine.

[ken o]

speedometers have been off for a long time.
http://www.caranddriver.com/features...ometer-scandal

[Trendie]

Makes you go 0-60 faster!

[Strider]

ok, that makes me feel better. Haven't gotten a chance to look at my tire size yet but that makes sense how it can change off set of speed. Mine too is fine and matches up till about 45 mph and then it gets worse and by the time I get to about 60mph it is off by 5. Which is fine cuz I think I'm going 5 over when I'm actually not. LoL.

[chriscar]

Well it's going to be off a set %.... so as your speed rises, the % difference stays the same, but the net effect is higher as your speed rises.

C