[bleedcummins]

i here on my 02 with 3.55 gears that putting 35s on my stockers instead of 33s will lose mileage is this due cuz bigger dimension or the weight diff?? so less say stock rims and 33s weigh 55 each and with 35 is 70. well if i got some aftermarkets and with 35s on the they weigh 55 each like the stocks with 33's would the mileage not change cuz its the same weight?? or is it just due to the fact that the 35 is taller and would be a little wider (12.50 vs. 11.50)

 

[bleedcummins]

anyone have an idea???

 

[oldsmobiledave]

multidimensional

There are many things in play here.

Things that increase fuel economy....

Narrower tire....less rolling resistance.
HT vs AT vs MT....also less rolling resistance.
Diameter...to a point tall tire = lower RPM
Less Weight....smaller tires & lighter rims

& with weight you have both total mass & unsprung weight but the latter is irrellevent in this application

However you can go too tall & be out of your optimized rpm range thus lugging the engine & killing economy.

Taller tires tend to be heavier so this adds weight.

Taller tires raise the truck so the vehicle is less aerodynamic & lessens fuel economy.

There are many factors here & the answer you are looking for is not a simple one. In general you want to run the lightest rim you can with the tallest tire that works for your driveline combo (trans & final drive ratio). Keep the tires narrow without being cookie cutters (because let's face it they look like hell) & you will improve your fuel economy.

Hope this helps....:thumbsup: