speedometer

I have a "new" Rough Country speedo calibrator, $75 (new $295). I had to swap because my rear-end gear ratio couldn't be set on this and I wasn't getting the shift points I need and I waited too long to return it. Works great and firmware is updated, not married to the vehicle. Will ship.

7in screen all digital premium speedometer with roughly 11 miles. Replaces the analog cluster with the small monochrome 3" screen to the all digital 7" color screen. Dealer can correct the mileage or you can use a mail in service. Like new condition. Will add off-road pages to the cluster...

Upgrading my Gladiator Sport by adding Rubicon take-off's springs and shocks along with 35" tires on 17" wheels with a 3.73 rear end. Yes MPG goes down (none of us on here buy any kind of Jeep for the MPG anyway), and the heavy tires will be tough on the 3.73, but I had same setup on JK with no...

So obviously when you up-size your tires it will throw off your speedometer. Is there an easy way correct this?