I have a 2002 screw with 5.4 engine and 17 in. tires with a .355 rear. I was wondering if downsizing to 16 in. lower profile tires would improve the power, since the 17s seem a little tall for the 355. I guess I could go down to 373s but seems the cost would be about the same as for new rims and tires. Would both mods help in the power area? Would this help more on low end or high. I am sure some of you guys have tried this after looking at the serious mods on some of you rigs. Mine is only a month old, (got the 02 because of great rebate) and bone stock for now. Next week getting magnaflow and fipk. Any assistance will be appreciated.

 

papa,

The smaller tires will most certainly provide for more low-end torque and better acceleration, it's the exact same result as changing the final gearing in the differentials. If you do this mod, don't forget to either have a new speedometer gear installed or have the EEC code re-burned by the dealer to compensate for the smaller tires.

The change of the tire OD is the exact same as the change of the ratio of the rear end. The distance around the tire is 3.14159*OD and since pi is constant, the ratio is directly proportional to the initial and final ODs.

% ratio change = ((Initial OD-Final OD)/Initial OD)*100%

Hope this helps you decide what you want to do and how much tire change you need to achieve a relative change which is the same as a 3.73:1 final ratio.

~DM~