Hey gang... Haven't been around in a while, been busy. I have kinda noticed something strange about my '00 LS the speedo is almost always slow... like by 5 or 6 MPH, but not all the time. I clocked myslef with a stand alone GPS, and low and behold, I have to be doing almost 5 over to do the posted limits.

This is the weird part, if it was tire size, then I would expect to see it be off by a percentage, like 1 mph at 10, 2 at 20 and so on. I'm off by about 5 or 6 from 20 to about 65, then it kinda varies. I took it up to 100, and the GPS clocked a max of only 96. I'm running the "alternate" size of 17's, the 245 45 I think it is.

Anybody else seen this? I have dug around on some other posts, but I haven't seen this issue yet... Or do I win the prize for the strangest :q:q:q:q category again??

I have 235/45 17's, and the speedo isn't off as bad as yours. Mine reads about 2-3 mph faster than I'm actually going. At about 65, I'm actually going 62-63. I've gotten used to it though.

I have 235/45 17's, and the speedo isn't off as bad as yours. Mine reads about 2-3 mph faster than I'm actually going. At about 65, I'm actually going 62-63. I've gotten used to it though.

What I don't understand is how it can be off by a constant 5 mph, if it's tire size, then the faster you go, the more difference you will see. It's almost as though they want you to think you're going faster than what you are. Another interesting point is the milage is off just a little too... which makes me wonder when my warranty really ran out...

right - it's a percentage difference - if your tire's circumference is more or less than stock then you'll see the same % error in the speedo

I wouldn't completely trust the GPS to give you a 100% accurate reading of your speed. The GPS in my truck usually shows me to be going about 3-5 under at about 65mph.

Don't know if it is the speedo or the GPS that is inaccurate. I don't worry about it as long as I have a rabbit in front.

Good Luck,

Jim Henderson