So i got the 15x8 ford wheels on with some new 30x9.50 A/T tires and i definitely notice the speed difference (I was expecting it). I want to say the speedometer is reading maybe 5-6 mph's lower than it should be.

Can i get this reprogrammed at the dealer or maybe something i can do? I know for some chevy and ford and dodge trucks, they sell 'hypertech power programmers' that allow you to compensate for bigger tires by plugging the programmer into the OBD2 port and fapping away on the buttons.

Thanks in advance. <img src="/forums/images/graemlins/wink.gif" alt="" />

You can't do it by fiddling with our ECU. We have a direct connection to the speedo (electrical) with a splice off to the ECU, in other words our speedo is not driven off the ECU like some vehicles.

There is a kit sold in Oz that does speedo corrections, 1% at a time from -99% to +99%, available here .

There may be someone in the US that provides a similar kit, or you could purchase from these ppl (International orders OK). Box sits between the speedo and the VSS and is adaptable to most VSS's (optical, hall effect, perm megnet/coil).

I'd check it against a GPS first and see how far it actually is off. Mine is fast by 4 or 5 mph at 70 with 205 x 75 x 15's. I figured with 225 x 75 x 15 it should be right on. 235's is should be a couple of mph slower.

Speedometer Calibration

In the US there is something called a Yellow Box that can be installed. Thinking about buying one.

Everet

I run 30's and the diffrence is only 5 kph, i have a gps so I can compare the diffrence. Since the spedo has a 5% error rate anyways, the 5 kph caused by the bigger tires is not a real issue for me, well not a big enough issue for me to plunk down more $$$$ on another gadget!

Yes I had noticed my speedo was somewhat optimistic also, I figured out 5%, that is 3 mph at 60, 5 km/h at 100, in line with IRON and Homerdog findings...

x2! <img src="/forums/images/graemlins/kewl.gif" alt="" />




...Famous words of Sir Fokion..."It Doesn't Worth It!" <img src="/forums/images/graemlins/smile.gif" alt="" />

I have 31x1050s on mine and with a GPS mine is 16% off (50=58 mph, 100+116 mph, and so on). I have checked what my speeds should be at differant speed limits and in 100,000+ miles (116,000+ corected) I have recieved 0 tickets. Just drive a little under the limit and you should be fine.
your speedomter isn't just 5 or 6 MPH off, the faster you go the more its off.

Dennis

oops, 100=116 not 100+,116. It doesn't matter how many time I prof read I always miss something.
Dennis

That's what I come up with too. A $100 item can save you a lot of grief!!! Last speeding ticket I got was about $400 (not in the sportage)
Your math is ok.
Everet <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />