From Lexus 15" To Lexus 16" Wheels On My 1992

[j.barleycorn]

Hope someone can help me with the age-old question: If you put larger wheels/tires on a vehicle, would you expect a dramatic decrease in gas mileage?

I recently bought and installed OEM 16” Lexus wheels (1995-1997) on my 1992 LS400. These came with brand new 225/60R16 Pirellis already mounted and balanced. These replaced the stock 15” wheels and 205/65R15.

The car looks much better with the extra inch, BUT….

My MPG on the first tank since the swap went from my traditional average of 25 MPG to 22.7 MPG.

Now I am aware that heavier wheels/tires will take more energy to get going, keep going, and stop, but is this size drop to be expected?

When the LS400 went from 15” to 16” wheels, I can’t believe that other changes we made that compensated for the weight and added the MPG back somehow.

And why can’t I get my head around how the car is calculating distance? Unless I am drunk, each axle rotation with a 16” tire would make the car go a little further than with a 15”.

According to tire conversion calculators, when my speedometer reads 60 MPH, I am really going 62.7 MPH, or about 5% faster with these new tires. Would this therefore mean when my odometer reads 100, I have really driven 105 miles?

Obviously I would like to think I did not hurt my mileage TOO significantly for simple vanity purposes.

On a related note, I also recently put 16” Tundra wheels and 265/70R16 Pirelli Scorpions on my Tacoma (replacing the 15” stock wheels and P225/75R15 tires), and watched my MPG immediately plummet from 22.5 MPG to 20.5. (The conversion on this swap was more like a 8+% speedometer change: when reading 60, the true speed is around 65).

So: has my mileage really taken the dive, or is my odometer playing tricks on me?

This is all wishful thinking, I’m afraid!

[akewlguy]

Damn no wonder my 17" get about 23mpg.

[SRK]

The 16 inch setup has a much larger rolling diameter than the stock 15 with factory sized tires. Your speedo is simply counting wheel rotations, and there are now fewer of them for any given distance travelled. Also the final drive ratio has been changed a bit, so the engine is actually working harder to accelerate the car. Your mileage seems about right.

I have often thought that if I got a set of 16's for the 92 LS I would drop the profile height and keep the same overall diameter.

[akewlguy]

Ahhhhh... I forgot about something.

This cop pulled me over and I was doing about 78 or 79... He stated I was doing 83... I thought he was full of *BLEEP*, but listened. Hel did let me go but a few days later I realized my 17s put me about 3+ miles off (at 78-80 miles) per hour. So what does this mean..

Well if I think on a long trip I get about 22MPG... I need to add another 17 - 23 miles to that 440 mile trip.... That could give me an extra 1.15 MPG. So I am curious if I do say around 60 would I hit 25 MPG.

Might have something to do with the 10% decrease in performance

I suppose if this is the case that there is a 5% decrease then at 75 I would be doing about +3.75 or 78.75. So this would once again change my MPG by somewhere around the 1.15MPG.

YES I just increased my gas mileage by

Now my problem my LS hates to go less then 70. Also I love to cruise at 75 or now 80. Cheers