have you guys noticed a decreased MPG w/ this set up? i know the 205/50 is slightly smaller in overall diameter, so i guess the car needs to make revs to get the same speed as the 195/55... average driving conditions like hwy and city, not hard racing or drag... thanks!

 

you're way more observant than i am...now im going to be checking....

 

Since the 205/50/15 is a smaller diameter than stock, if anything, you should notice an apparent INCREASE in mpg. If you're calculating mpg off the odometer, you would see more miles on the odo than you're actually putting on. Say hypothetically, your wheels turn 2000 revolutions per mile on the stock size, so 2000 wheel revs turns one mile on the odometer. Imagine if you changed your wheels out to 2" rollerblade wheels. 2000 revolutions of those wheels would probably take you like 1/16 of a mile in actuality, but the odometer will show that you went 1 mile. Anyways... I'm rambling.

Make sure your tires are inflated properly. Maybe you're driving more aggressively because your tires have more grip now...

 

I'd say the <U>decrease </U> in MPG is due to bigger contact patch of the 205/50.
Just my guess.

 

it's not gonna be that significant.. if your noticing a big difference.. then put your stock shitty michelines back on.. LOL

 

hey you above me here, that is one HOT HOT HOT avatar pic.
your killinme, who is she?????

 

Toyo FZ4 205-50-15
i like it....i don't like the grip though its not as good....as others
but the size is good for

i like my 2.2 60's (dont' know how i get it!)
i like my 135mph topspeed runs
i like my turning ability
i like my 30mpg GAS

 

uh i doubt you'll be able to measure a difference..

 

This might be helpful...
http://www.miata.net/garage/tirecalc.html

It'll tell you exactly how much you're off mathematically.

 

I think it may have something to do with the pressure you're running in your tires.

I had 205/50-15 and now I'm running 205/45-16. The inside of the door recomends something like 36psi frton 39psi rear. Most sidewalls on 'performance' tires say 45psi. I found 40psi front 42psi rear was good for grip, mileage and wear. I'm thinking if you stick with the factory suggestions the wider tire would have more rolling resistance.

Just a thought, but a few psi can make a big difference in your mpg.