demonicgenesis

When you do a +1 size in tires, your speedo will always have some kind of miscalculation, even if its only 1 or 2 mph. That being said, has anybody checked to see what the difference really is between the stock genesis 18” rims and 19”? If there is a difference, then is there something different in the programming with the speedo so that car knows if it has either 18’s or 19’s on it?

majik

I would think all cars are off by 1mph or so. I really don't think it's worth even checking.



People mention speedo so often when people want to go with a larger wheel, but I just don't think there's that big of an impact. Most calculators will show 1-3mph variance, but I'm usually going 10-15 over anyways so it doesn't matter much to me.



Have YOU check to see the tire size comparison between 18" and 19" OEM to see that the actual radius difference is?

PandaSmuggler

I Am Not A Wheel and Tire Expert but...



AFAIK, the 19" wheels use 245/40/R19 tires while the 18" use 245/45/R18. Per this website, your speedometer will read 60mph when you're actually going 60.2mph.

Red Raspberry

I've found the speedo to be off by +2 mph. This is compared to a GPS and the OBDII readout. This implies it is intentional and is only on the displayed speed. I had the factory 19", got some factory 18" for winter an have factory sized aftermarket 18" wheels and tires.



The factory 18" and 19" are very close to the same diameter.