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Tires choice for road trip...?

Discussion in 'Ram Trucks' started by streetsurfin', Aug 24, 2007.

  1. streetsurfin'

    streetsurfin' Senior Member
    Messages: 770

    I am taking a 1600-1800 mile (total) road trip in a 96 1500 Ram. Tires on it now are 305/70-16 Cooper Discoverer AT's on A/R wheels. Truck is a 4x4, has a 3" body lift, automatic, 360, and I believe the gearing is 3.53:1. Which ever is Dodges mid to high 3's gearing, I think. I looked at it once but have forgotten the exact figure (Truck new to me since June). I have another set of tires on the steel rims which are 235/85-16 Goodyear Wrangler AT/S's. Tires spec'd for the truck are 245/75-16. By my rough measurements the 305's are about 33" in diameter and the 235 just under 32. I am wondering if it will be well worth it to switch over to the 235's for better fuel mileage for this trip. I'll be towing a small single axle trailer with 1,000#'s on it. I'm not too worried about the power difference to pull the trailer since it is not that much weight. I am trying to do this with a lower fuel expense if it will make enough of a difference. I am guessing I could save $85-$100 in fuel (@$3gallon) by switching if it gives me an actual (remember the speedo is off due to the larger tires size) 2 mpg increase. If I only saved 25 to 50 bucks I don't know if I would bother. I cruise at a speedo indicated 65 in 3rd @ 2550 rpm, 1750 rpm @ indicated 65 in O/D. I will likely be going between tow/haul and O/D since it is such a light load. Trip is between Illinois and Kansas so it is flat for the most part.
    There are weights on the 235's rims and the previous owner took extremely good care of the vehicle so I assume they are well balanced. With the 305's and no fender flares the potential for fender and rocker panel chips is higher. I am registering 10 mpg now but I know it isn't accurate because of the speedo being off from the larger tires. I thought I should be able to get at least 12-13 out of this truck. I am trying to think if there is any other info I can give before I ask if any of you think I should make the switch for the trip. Of course the 305's and rims look boss but they put me at risk of theft if I have to stay over in any bad areas. I also get the impression the police would pay more attention to me in the 305's. In other words less conspicuous may mean less down time on the side of the road visiting with the man.

    So, What Would You Do? Would the 1" difference in tire diameter and the extra width cause much more fuel consumption, by moving me out of the optimum power range of the engine and increasing the rolling resistance? How much difference - 1 mpg? 2mpg? Would you switch the tires for such a trip.
    Last edited: Aug 24, 2007
  2. streetsurfin'

    streetsurfin' Senior Member
    Messages: 770

    Too Late

    No need to answer now. I decided to do the trip without switching over. Leaving in the AM. Thanks anyway.