Kevinlane

Anybody ever use oversized tires and wheels in order to raise the gearing and therefore lower the RPMs at cruising speeds?

I’ve wanted a bit more gas mileage would going to a taller tire give me a noticeable difference of longer gearing?
I’m thinking about going with a 215 45 by 17” That should fit if I don’t lower.
Tire calc page says that it would be a 4% difference. i.e. 60mph vs 62.4(after the change)
Again, this is a daily driver that I want a bit better looking and a bit better mileage.

Anyone else try this method with a P5?

Roddimus Prime

I haven't done that particular tire trick but I do switch to smaller 15" rims when I drag race to help my 60' times and trap speed.

I found by going from the 16" wheel to a 17" mp3 wheel cost me .3s in the quarter mile....just keep that in mind when spending money on rims and tires.

Kevinlane

NO big to me, this is a daily driver and I do a 40 mile commute. I got a P5 because I liked the styling and reliability seemed pretty good. I'm happy with the purchase so far, but I'm a tweaker by nature so I'm wanting to squeeze some mileage out of her if I can.

Roddimus Prime

if you use a taller wheel tire combo you're going to end up burning more gas than you'll save. You'll have the same amount of motor trying to turn a heavier/larger wheel.

goldstar

For a small but noticeable improvement in fuel mileage, switch from mineral to synthetic engine and transmission oil. The reduced internal friction provided by synthetics is the key here. I use Red Line SAE 10W-30 in my engine and Red Line MT-90 (SAE 75W-90) in my manual transmission. If you have an automatic, I can't advise you there.

Of course there are many other benefits to using synthetic oils besides improved fuel mileage. You can learn about them by doing a search. Check out the Red Line oil website for starters: www.redlineoil.com

Kevinlane

Roddimus, do you KNOW this or is this an opinion based on your experience?
I know you got better drag times with the smaller diameter wheel but did you or anyone you know try this and get the lessened MPG you're referring to?

Keep in mind I go over the "SAME BORRING ROUTE" daily and this car seems like it will easily pull the grades I need it to (of course this is a guess)

If it just wouldn't turn about 3700 rpm at 75mph!

Roddimus Prime

this is common sense and basic physics. Don't take my advice...take Newtons.

A larger wheel will more likely be wider, heavier, and taller. This increase drag, unsprung weight and rolling resistance. These are all things you try to overcome in order to get better gas milage.

it is my OPINION (since no'one has done any ACCURATE testing on this) that you will see a slight decrease in performance and mileage. I also want to say that even if you used 15" baby spares at all four corners you'd probably not see any gains in mileage. These are small changes and won't affect your gas budget by a noticeable amount.

goldstar

A larger diameter wheel/tire combination will effectively raise (lower numerically) your overall gear ratio. This will definitely be beneficial in terms of increased fuel mileage, at least to a small degree. At the same time, the increased wheel weight, along with the increase being primarily toward the outside of the wheel, will reduce your acceleration to some degree. Since you are interested in economy, not performance, the larger tire is the way to go.

02 DX Millenium Red

Racing Beat

want better mielage, reduce weight in unsprung and sprung terms, increase airflow into and out of motor, lower car to reduce drag on underside bits, keep waxed and super clean all the time tor educe CD, keep windows up and sunroof closed, throw your AC in the trash

ricerocket97

I just put some 17" rims with some toyo proxy tires on my protege. It didnt change anything as far as i can tell as far as gear ratios or anything like that. I still do 3200rpm at 70mph. but maybe i am really going 72 or something like that and my gages are wrong.

gottacatchup

if you want better milage drive close to 3000 rpm. I belive thats the magic RPM where are car runs the most efficeintely. even though driving faster should get you there faster you´ll burn more fuel cause of the higher rpms. Also just dive more carfully around town, changin you´re rim size by an inch or two will not make a huge difference as our cars already come with lightweight aluminum anyways.