Low MPG with 33s R18 load E tires

[jludave]

Thanks for the replies, I have a sport altitude that came with 32s tires so would the difference from 32s to 33s be big enough to impact the transmission shift and MPG? Do people that move from 32s to 33s usually use the tazer?

I have a Sport Altitude. I had 33 inch tires (Cooper Discoverer AT3 XLT in LT275/70R18 E range) installed on the stock wheels about a month ago. I drove it for a few days before receiving my Tazer. There wasn’t a huge difference, but until I updated my tire size with the Tazer, the transmission shifts were a bit off. My speedometer was also off by up to 3mph at higher speeds.

It definitely makes sense to program the vehicle for the correct tire size. If you want to save a few dollars, you can purchase a bypass cable, OBD2 reader and use the JSCAN app.

Sponsored

 

[Lioska]

I have a Sport Altitude. I had 33 inch tires (Cooper Discoverer AT3 XLT in LT275/70R18 E range) installed on the stock wheels about a month ago. I drove it for a few days before receiving my Tazer. There wasn’t a huge difference, but until I updated my tire size with the Tazer, the transmission shifts were a bit off. My speedometer was also off by up to 3mph at higher speeds.

It definitely makes sense to program the vehicle for the correct tire size. If you want to save a few dollars, you can purchase a bypass cable, OBD2 reader and use the JSCAN app.

Thanks for the reply, this helps a lot. I guess I will go ahead and get the Tazer to correct the tire size.

 

[Black Jeep Convertible]

Thanks for the reply, this helps a lot. I guess I will go ahead and get the Tazer to correct the tire size.

Don't feel bad about getting the Tazer, mine already paid for itself with Tire Size change, Auto Stop Start memory, LEDs and when I finally get 35's, it'll pay for itself again. Plus the light show is pretty cool.

 

[OldJupiter]

Hello! Sport 2018 2.0T owner here. Had the Stock Steelies on the 245 Bridgestones. Got 28 mpg on my 60 mile round-trip daily commute in 2019 50/50 City/Highway near the NYC GWB. Stock calibration.

Upgraded to the 285/75.R17 Falken Wildpeak in 2020 - same commute about 22 mpg max taking more back roads this time - stock steelies! No recalibration.

Present day: Mopar lift/ Black Rhino wheels 17 inch x 8.5inch / 37x12.5 Falken Wildpeak - Same commute down to about 20 mpg. I did recalibrate to actual tire size of 36" measured. Please note my rear axle was replaced under warranty Dana 35 rear. Recalibration helped the transmission a noticable amount in terms of shifting. I ran without the recalibrated speedo for 1 week and got only as high as 17 mpg.

These calculations were cross checked with gas receipts + trip information.

I have a heavy foot, but an eye for smiles per miles. I'll push when needs pushing.

 

[Headbarcode]

Reprogramming for the larger tire will most certainly have a negative affect on fuel economy. The speedo being off will taint the vehicles mpg readings, and feeding the 8-speed auto wrong input will prevent it from being able to perform optimally, which will further taint mpg.

Another big contributor to your lackluster fuel economy is those heavy tires. Every pound of physical weight gets multiplied by 3 or 4, when it comes to rotational mass. So a 100lb wheel and tire combo would have a 3-400lb affect on the Jeep, per wheel.

Sponsored