[High.Breed]

What is the biggest rim size in terms of width and diameter i can fit on a prius before i need to do any major modifications?

Maybe along the lines like that ?

 

[hybrid-driver]

When you say something along the lines like the one above, I will assume you want your Prius ride height to be similar to it. Well we can safely say that going any bigger than a 18 inch wheel with that sort of stance will cause rubbing. Width, can't go too wide on these, they were mainly built to be a A to B car. 9 inches wide is what i've seen the widest on a Prius

so 18x9

 

[much2green]

18x9 seems pretty wide, and would lower the Prius fuel economy by a lot, giving it heavy wheels and a such a width that isnt needed on the Prius.

Id just go for the volk only prius made wheels only weighing in at 10 LBS each.

 

[zeeshan002]

18x9 seems pretty wide, and would lower the Prius fuel economy by a lot, giving it heavy wheels and a such a width that isnt needed on the Prius.

 

[Evilwillieg]

I managed a 19" wheel from and Audi R8 and its 11" wide

 

[LDB]

That's got to be good for mpg.

 

[Easy Rider]

That's got to be good for mpg.

What exactly are you referring to.....and why do you think that ??

 

[LDB]

I'm thinking 19x11 is going to kill the mpg and made a joke about it.

 

[Easy Rider]

I'm thinking 19x11 is going to kill the mpg and made a joke about it.

It's hard to pick up sarcasm from plain text.
This helps:

 

[bobbyprius]

No really, how is your MPG after those huge wheels were fitted? I did not know that the R8 had the same offset as a Prius? I hope you got a great deal on them, lovely wheels in their own right!

 

[bobbyprius]

No really, have you measured your mileage after installing those wheels? I had no idea that the Prius had the same offset as an Audi !!!! Hope you got a great deal on those wheels, they are lovely to look at.