lower top speed and mpg

[bam72091]

Since I put on my rims and tires I havent gotten better than 23mpg and Now once I hit 120mph my car wont go any faster when I used to be able to hit 127.

[SLEEPS]

I hate to ask because I fear I allready know the answer but, what size wheels and tires did you put on?

[bam72091]

225/40r18

[bryanguystatus]

SAME HERE!! MPG wise, haven't been on a closed track to test top speed.

[SLEEPS]

You do realize the larger diamiter wheel is heavier and takes more to push? Gas mileage and overall top speed would be effected by this.

[bam72091]

I was on the highway at 5am lol Do you think maybe I was going 127 but because of the bigger tires the speedo would be 7mph off I feel like thats to much. Or is my car less aerodynamic because of the bigger tires and an increase in drag.

[bryanguystatus]

If you have an ex then when your Pedro shows 100 you're going apx 100.96 ish mph. Forgot the exact number. I used to drive fast on public streets but felt I was pushing my luck to long. But it is because the tire is bigger, wider, heavier, and so is the rim. Just slap a turbo on there and it'll go up haha. That is a joke though but you'll get your top speed back.

[SLEEPS]

Metal weighs more than air and rubber, so you added weight overall to the car and added more mass to push and keep rolling.

[fredycrudas]

You are getting the same MPG and same top speed, but since you modified the tire and wheels the odometer is reading a larger diameter it always happen whel you get bigger wheels, it has nothing to do with the wheels weigth.

[SX FORTE]

Your rolling mass puts more strain on the engine so to speak, not that it will hurt it but it's using the little extra power you used to see in acceleration and top speed to turn the bigger heavier wheel. Rotational mass weather it be a fan clutch or bigger wheels, etc is going to rob your engines performance...why do you think light weight wheels, pulleys etc costs so much? Easy but expensive gains. A wider tire also increase drag which hurts your fuel economy, and everything else but grip is better...I find the stock 17's to be a nice compromise of performance and economy while slapping some better rubber on them.

[scarboy6693]

Probably the case, I've been planning on keeping 17" wheels that are the same size as the stock wheels on my SX.

[in10sive]

I don't think it will make that much of a performace difference going from stock 215/45/17 to 225/40/18 - it is a couple of inches more - think the wieght of the wheel will be the only factor but still don't think you will notice any perf loss...

[Maximilien]

Originally Posted by fredycrudas

You are getting the same MPG and same top speed, but since you modified the tire and wheels the odometer is reading a larger diameter it always happen whel you get bigger wheels, it has nothing to do with the wheels weigth.

It sure does....additional Unsprung Weight and Rotational Mass, make a great deal of difference!

Originally Posted by in10sive

I don't think it will make that much of a performace difference going from stock 215/45/17 to 225/40/18 - it is a couple of inches more - think the wieght of the wheel will be the only factor but still don't think you will notice any perf loss...

Yes....Google Unsprung Weight and Rotational Mass

[trevorusn]

All of the above. Yes, there is a slight weight increase, but your speedometer will also be off as the new wheel size combo is not calibrated to what your gauges read out.

[bam72091]

Anything i can do to counteract it.