Ok so I've been looking to get a set of 16" steels for my trail hawk. My question is if I go from a 17" wheel to a 16" wheel, will the speedometer be off?
It all depends on the tire you put on. You can get almost the same size diameter tire on a 16" as a 17". You start with a 215/65R17, if you got to a 225/65R16 it would be almost the same size. But I'm sure if you are going through the trouble of switching to 16" rims you are going to go bigger. How much bigger will determine how far it is off.
Im no expert, but most people only report 1-2mph at highway speeds, so not a big enough issue to be concerned about in my opinion. However, the odometer will read a little differently as well, by how much im not sure though. Maybe someone else can chime in on that.
It's when you step up to a larger tire. Much large I should say. The small increases we can do on Renes will be slight, even the 2 step up sized may throw it off 2-3mph. Nothing drastic
I just changed from 215/60/17 to 215/70/16, nearly 3% bigger diameter. Normaly, also speed changed that much. Now speedometer is more accurate. Before was bigger difference between GPS and speedometer. At 130 km/h on speedometer , GPS showed 123, now shows 127 km/h.
I've looked at this as well. And it's a proportionate change. If it changes 1mph at 20mph, it could be off 7mph at 55mph, etc. follow the link below, put in your factory tire size and new tire size, it will show you all. http://www.discounttiredirect.com/direct/infoTireMath.do Also, I'm very curious if Jeep is able to change the ECU or whatever to recalibrate to the current tire size. I know many other Company's will. Jeep of all should be able to!