Custom tires

F8L has done most of the research on this, he claims it is mostly aerodynamics, wider tires are less aerodynamic than narrower tires. Wheel weight will change acceleration, but not steady state MPG.

 

Rolling resistance is much increased with the 17" tires as is aerodynamics. I feel the hit is mostly due to rolling resistance, however. You can instantly feel the difference between 17s and 15s upon acceleration.

Expect a minimum of a 4mpg hit with the lightest wheels and best LRR tires. It will be even worse for heavy wheels and non-LRR tires.

If you do a search you'll find a ton of information on the subject. The hit is worse on the GenII than on the GenIII.

 

If you still want to maintain status quo in terms of mpg, I think your best is to aim to maintain the same circumference of the new set up with just a slight increase in tire width. In my experience, I changed from a 195/60/15 to a 205/50/16 on lighter wheels and non-LRR tires. It's almost the same circumference and just a 10mm increase in width. Honestly, I didn't feel any mpg hit. Maybe I was still in the process of improving my skills that's why I never saw the upgrade as having an effect. Now I'm doing way better than when I was on stock. I guess you just need to compensate for it by learning to drive more efficiently, which I'm sure you will when you get the upgrade done. So go for it!

If I had to go for 17s, I would've chosen a 205/45/17 or a 215/45/17 if my base tire was 195/60/15 as they closely match the circumference and don't stray too much from the width.

 

the larger the rim the more energy it takes to move the weight of the metal. The metal weighs more than the rubber too. think skater in spin and arms moving in and out. Conservation of angular momentum. The 15 inch rim is higher mpg and faster acceleration.

 

THIS is not correct. Call any major tire retailer and the sales people will tell you this is wrong.More rubber is more rolling resistance and more weight. Wheel weight is highly correlated to mpg. Hellooo??? Think about it; if the wheel weighs ten times as much do you think it will take the same amount of energy to keep it turning? Exaggerate the (scenario) weight and think about the consequences... Do you think it will take the same amount of energy to push a heavier wheel up a hill? Unless rolling down a super long low angle slope, the weight of the heavier wheel will not benefit you at all.

PS: I thought this reply was to a response farther up in the conversation. But the rebuttal remains valid.

 

You keep digging up threads to use this same reply. Please do more research on the subject.