Hi
I have 32" all terrain tires now on my 04 ram hemi 4x4 and am looking at getting 34" tires put on. Does anyone think there will be a huge difference in fuel mileage?
any help appreciated

 

There will Definately be a decrease in mileage. I don't know exactly how much but I went from 33s to 35s and lost about 1.5 mpg. Besides the added weight, the speedometer will not be properly calibrated unless you have a tuner to correct it. It's not something to do if mpg is your primary concern. It looks way cooler and was worth it imo.

 

You'll lose some torque. Your highway RPM will drop. As for the speedometer/odometer error, that isn't a big deal. Just know you went further on that tank (and you're going faster) than the instruments indicate.

You're making the effective gear taller, so your highway mileage may see a slight improvement.

 

Your in-town mileage will drop probably about 2 mpg and you'll lose some low end, basically because you've added weight and lost a mechanical advantage due to a lower effective gear ratio. On the highway you may stay close to where you are now since your gearing will be numerically reduced so your engine RPMs will be slightly lower which may counteract the weight. But moving the weight of the tire physically farther from the hub losses efficiency as well.

Another large factor in performance and fuel economy is if those 34" tires are wider and/or have a more aggressive tread. Both create more surface friction with the road and require more power (and fuel) to overcome...