And the whole car.....

 

I don't keep precise records of my gas mileage, but I do know I always get in excess of 20 MPG. Usually around 21 or 22. Those numbers are much better than my daily driver Silverado.

IMHO, the improved handling I am experiencing with my SO4 245/285 combo more than outweighs any small loss I may have in MPGs. It's a performance car and I want it to drive and handle like one.

Lou

 

Hey ROSSI just wanted to thank you for the photos of the future set up ( minus the front springs ) looks great. Very cool of you. The car looks great. I can tell the front is slightly larger than the rear but pretty subtle

 

To me this comes down to preference for those how are more concerned with gas mileage then oem tire size may be the way to for those folks, and for those people that are concerned with better performance at expensive of some loss in gas mileage then going wider is fine.

I'm with Lou on this one currently running 245/285 conti, to me improvement in handling is worth loss in mileage especially after installing I/H/E. I was spinning rear oem's like bicycle tires lol. What ever works oem our wider can't go wrong with either choice.

 

The front sidewall for 245/275 setup is 3.25mm taller than rear.
The 2008-2010 OEM size the front sidewall is 0.75 mm taller than rear.
The 2012+ OEM size the front sidewall is 1.25mm taller than rear.

 

Very informative thread, thanks you guys for all the info. Now I'm excited to get 245/30/20 in front and 285/25/20 in rear instead of the 245/35/20 and 285/30/20 that were on the car when I bought it. I average about 20 MPG since I got the F about 6 months ago and it would be nice to see a slight improvement in MPG by making the OD much closer to OEM.

Now I just need to wear my tires out faster - they look like they have identical tread since I bought the F.

 

^^^^Your really aren't getting an accurate MPG reading, because your current wheel/tire diameter is off by 1".

Lou

 

In addition to increased width, I found that more expensive softer compounds would kill my gas mileage. I wasn't sure however if it was more due to the rolling resistance, or the fact that I was more willing to be on throttle in the lower gears because of the traction.

 

I think people here need to mention how many street to freeway driving ratio when they mentioned their MPG's. I would seriously doubt anyone here who has mentioned they upgraded their tire width to 285's and average 21+ mpg's do mostly street driving.

In addition to a wider and heavier tire, (most of the time) you also upgrade your wheels to heavier wider ones. I've never seen 20+ mpg on my car for that reason. It doesn't bother me because 305's look awesome on an ISF!

 

2008 ISF - Cronus
MODS done: Sikky headers, custom exhaust, Injen intake

^^^All those affect gas mileage more than tires. Also, your right foot affects your gas mileage like crazy. Stop sweating the small stuff. If you're worried about gas mileage, go buy a Prius or a Leaf.

 

^^^^All the mods you mention do affect mileage, but in a positive way, due to making the F more efficient. UNLESS, you put you foot in it, which those mods would entice you to do.

The wider tires are the only performance mode that negatively affects mileage decease of the added drag and the added unsprung weight.

Lou

 

Efficiency does not equal better mpg.

To get those mods to achieve similar or better mpg as stock would require a tune.

 

^^^^I disagree

Lou

 

Enlighten us how I/H/E will give us better mpg.

With actual facts, not bro-science, butt dyno etc.

 

I am getting aftermarket wheels...not sure exactly which ones yet but as an example I am looking at this set up:

Front = 19x8.5 +35mm
Rear = 19x9.5 +38mm

The guy I am working with seems to know his stuff and is strongly suggesting the following:

Front = 245/35/19
Rear = 275/30/19

He says they will fit with "no rubbing" although he may have to heat up the plastic under the front fender to make sure? I know many have done this and it is really not a big deal.

However, I want to lower the car eventually...Tein or Eibach??? And I am thinking that his setup (tires) would have issues so I am thinking about going with this setup:

Front = 235/35/19
Rear = 265/30/19

This would bascially be the same setup as Joe Z... see https://www.clublexus.com/forums/is-...-f-wheels.html and he seems to not have any problems and this is a daily driver.

So if I go with my setup what would be my issues other than the fact thay this setup would be smaller diameter causing my Revs per mile to increase...and what does that really mean and how does it affect the car...also this setup would be lighter (total weight) as the tries would be lighter that the 245/275 set up...thanks.