Gas mileage drop with 30's? And will they fit?

I have 225x75x15's, and am going to put on a set of 30x9.5x15's. I was wondering if I will notice any drop in my gas mileage. I have a 2000 chrysler 8.25 29 spline in the rear and am not sure whether it has 3.55's or 3.73's.

Also I have heard that 30x9.5's won't rub without lift. Is this accurate? If not, I do have a set of .75" shackles and spacers that I can throw on.
Any suggestions?

cainraiser21 said:

I have 225x75x15's, and am going to put on a set of 30x9.5x15's. I was wondering if I will notice any drop in my gas mileage. I have a 2000 chrysler 8.25 29 spline in the rear and am not sure whether it has 3.55's or 3.73's.

Also I have heard that 30x9.5's won't rub without lift. Is this accurate? If not, I do have a set of .75" shackles and spacers that I can throw on.
Any suggestions?

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You will notice a gas drop only because your speedo will be off. Bigger tires ='s less mileage on the odo. So it will appear you are going less miles for the same amount of gas. Most likely about 10% less.

yeah the odometer is really the only thing that you need to worry about. Gas mileage should stay about the same, maybe slightly lower.

a.) they should fit. Ok, they rub when you hit a speed bump while doing a donut big deal.
b.) the gas mileage should not be affected dramatically
c.) there should be a small tag on the cover of the axle identifying the gear ration
d.) I run 30's and I am still trying to find a reason to believe my speedo is off by any noticeable amount. The circumferance difference is not that much but the do seem taller, maybe don't collapse as much.