jeep tire question

i have a 2015 jeep wrangler with 255/70/18 tires 45000 miles tread is getting low,have available 225/75/16 tires,can i use them with no problems?ome tire is 32.1 inch overall other is 29.3 inch overall hight,years ago F/60/15 had same hight as f/70/14so you could have same spedo pinon gear,will there be a spedo issue??

Yes the speedometer will be off. A dealer can reprogram your computer or there are programmers you can buy to calibrate it your self. Better make sure the 16 inch rims clear the brake calipers and rear sway bar links.

Thank-you for the reply,i did't think cars have spedo gears anymore,all electronic now days.wheels and tires came off 2016 wrangler 4 door!

You are correct, they are all electronic these days, however, they are still counting the revolutions of the transmission gearing. Those revolutions were based on the diameter of the tire the vehicle came from the factory with. When you change the diameter of the tires, the number of revolutions in the trans does not change, but the distance the vehicle moves per revolution is different. The difference between what the computer believes the vehicle travels because of a tire diameter, and the amount the vehicle travels with a changed tire diameter gives you an incorrect speedometer reading. once the computer is informed (reprogrammed to know) of the different tire diameter, the reading will be correct again.

In the old days, it was done with a gear change in the speedometer drive, these days its done by telling the computer what has changed. Gene

There still is a sensor that gives a signal that the computer sees. The computer can be programmed for the specific tire used. Common procedure is to use roll out basically tire diameter as a factor to use in the programming procedure. Dealer can do it or you can buy your own to do it yourself. Here is a video.speedo calibration