any one know if there is a program or box you can buy like the super chips and obd2 programers that trucks use. never really mattered much to me that the speedo was off but after a few long trips the gas mileage is really showings threw

 

nope sorry theres not

but you can get the scangauge II to help with that

http://www.scangauge.com/

just calibrate the scangauge and you'll be all set...

 

might have to try that but i figured there was something i know the shops that do big rim installs on suv have to be adjusting the speedo also

 

I've had lifted trucks before I put 20's on my xB and thought the same thing.

I ended up buying a ScanguageII. I would have expected the speedo to be off more than it actually is. Search the forums and you will find many people saying that the stock speedo and tires is off. Here's what I found;

The SG (Scanguage II) has a percentage adjustment for speedometer. When I first plugged it in it read lower (on 0% adjustment) than the stock speedo.

http://www.miata.net/garage/tirecalc.html <--- tire size calculator

OEM tires are 185/60/15. Stock tire sizes (per the repair manuals) are 185/60R15 or 185/65R15.

I am running a 225/35/20. That is 10.4 (or 7.1) percent larger than stock.

So with the 20's when the stock speedo says 60mph I should be going 64.2-66.2mph. I calibrated the SG with a GPS at multiple speeds. 15, 30, 45, 60, 80. The adjustment on the SG is 15% (this really means nothing, just a point of reference). I found that with the 20's my stock speedo reads 59 when I am going 60 and reads 80 @ 82.

I just switched back to the stock alloys for winter, however I'm running a larger tire (195/65/15) than stock. Once I re-calibrate the SG I will be interested to see if the stock speedo reads as low at it seems it should.

 

i have been on 20's since 05 and running the same tires you are and all new it was off a little since the bigger rims but i;m right the trd wheels are 19;s so it can make a lot the only thing i see it on long trips on the interstate it shows alittle less than factory but still worth it and i use to be on air ride then back to factory now lowered on megan springs 2.5 inch drop tucks lips lol

 

It may seem too simple but what's wrong with just figuring out how far your speedo is off at a certain speed and just reposition the needle accordingly so the speedo would be more right than wrong?

 

I just know how much it's off and do the mental math. They are never really absolutely precise any ways.

 

i dont want to mess with the needle plus if i take the wheels off then it is way off you know