i switched from the stock 16x6 wheels weighting around 18lbs to konig feather 16x7 at only 15lbs. i kept the same stock tire. around a 12lb savings total. accel and braking were noticeably improved, but anything over 60mph i am getting less mpg than with the stock wheels. the only reason i can think of is the konigs have a 40 offset and with the added inch of wheel they are flush with the fender. so is it that the tire and wheel now closer to the air traveling around the fit is causing aerodynamic disturbance and droping the mpg. or mabey cruising at higher speeds the heavier wheel helps maintain speed better? thanks for all input.

 

Skinnier ties usually get more MPG than fat tires, so I can buy your extra inch being part of the problem there.

 

Yup, rolling friction is a bitch.

 

He says he kept the same tire, or that would be my thought as well. I think I would buy the rolling momentum of heavier wheels theory.

 

Ah, missed that, haha.

Well going from a 6" rim to a 7" will make for a smaller overall diameter on the same tire because of the change in the angle of the sidewall, requiring the engine to spin faster to achieve the same speed. Also, if the wheel is flush with the car this would create smoother flow over the side of the car...

As far as the heavier wheel returning better mileage.. Remember less inertia to overcome makes it easier for the engine to turn as well as less total mass push along. Both of which would dictate less fuel is necessary to cover the same distance over the same period of time, and would make for even less fuel required during acceleration.

Tire wear also contributes to the shorter effective final ratio at the road, also dictating higher rpm for a given speed @ the same throttle position = more fuel per unit time.

The OP never states specifically how much his fuel economy suffered...

 

Stock tires. I agree on shorter height due to stretching the tire on a wider rim. Lost about 2mpg average highway. Gained 3-4 city driving.

 

Offset is your biggest enemy! Not because of aero, but because of the large mechanical arm you’ve just put on. That extra offset is like putting a cheater bar on your wrench…only you are putting all that leverage on your bearings. The faster you go, the more it pushes…and loads the bearings.

Tires are all secondary...aero in last place...for this instance.

 

Oh yeah... stretched tires for a shorter final gear ratio. I'll buy that one too...

I guess we don't have to send this one into mythbusters after all.

 

What you are saying about offset sounds crazy as hell... There may be truth in what you said based on the sounds I have been hearing when I kick in the clutch pedal that I didn't hear before I put wheels with more offset on my car. I just noticed it today for the first time and was thinking about it before I read your response.

 

i noticed this noise as well. i attributed it to stretching the tires. this is the only car i noticed more road noise on when i changed wheels and didn't change tires.

 

i think i may switch wheels to SSR type F. 16x5.5" +38 offset with stock tires. that should put me only 3mm wider than the stock wheel and tire at 6" wide with 53mm offset. but at 10.1 lbs each i will save about 32 lbs total wheel weight.

 

konig to ssr... now you're talking

 

Lighter wheels make a big difference in improving your car in ways that no other modification is going to but they aren't going to improve mileage at sustained highway speeds unless there are lots of hills on your route.....The weight of the wheels are like flywheels in that they take power to get up to speed but the rotating mass maintains speed longer when coasting.. Heavier wheels coast farther before slowing to a stop and can improve fuel mileage for someone that coast a long distance to a stop when hyper mileing.... In stop and go driving where hyper mile driving isn't used the lighter wheel/tire setup is going to award you with better fuel mileage and response when accelerating to speed from a stop and when changing speed up or down in heavy traffic or just driving in a carefree spirited manner.

 

I have Konig Forwards (16x7) w/40mm offset and then added 205/50's to them and have to say my mileage going back home to Detroit afterwards went from 38 mpg to 39 mpg and going home I used to get 43 mpg and it went down to 41.3 mpg, but that could be from anything from wind, fuel, etc.

How about a pic of those wheels on your car BTW

 

bullshit. theres so many factors regarding mpg that you couldnt measure the difference between the two different wheels.

 

Just sayin'

 

yeah man. air temp definitely plays a big role. in the winter i average 45mpg, summer 55mpg.

 

Wow, really? How? I'm quite jealous.

Do you have a sail?

 

what. I've only had my car for 2 months the best average ive got was 37mpg. WTF. I havn't noticed a difference between 70-90 degrees.

 

I just put the mugen front lip on tonight. Tomorrow I will get some pics up. The tire still sticks out of the wider front lip but nowhere near as bad as without.