Ok so I just got a 2005 HCH, the first thing I noticed about these cars is how funny the wheels look. They are small and awkward. I was going to buy some new wheels for it so Im guessing a 15” wheel or so should fit. I think the stock rims are 14” or some thing to that effect. Any one done this yet/know how it will impact fuel efficiency?

I know it’s a myth that larger tires give you better gas mileage but how much worse could they make it? I just want some thing decent, nothing fancy.

 

Search on this site, there are full threads (and pictures, even) of folks that have made the switch. IF you keep the width of the replacement tires reasonable, then the MPG hit won't be too harsh. But DO expect at least a couple MPG hit.

The replacement tires will likely NOT be LRR.
The replacement tires will likely be heavier.
The replacement tires will likely be wider (more rolling resistance).
The replacement rims will NOT be as aerodynamic.
The replacement rims will likely be heavier.
All these items affect MPG negatively.