I just put 17" Bullitt rims on my V6 that were originally equipped with 16" rims. As soon as I drove the car it felt sluggish in performance. It was perfectly fine when I drove it to the shop before the new wheels and rims. I've read how sizes such as 19" can decrease gas mileage and throw off the speedometer, but does one size really make a difference? I can deffinitely notice a difference.

 

Yes! I'm almost positive your 16 inch rims and tires were lighter than your new 17 inch rims and tires. Lighter = faster. Plenty of people report the same thing between the stock 17's and 18's.

 

You gotta pay to play whether it be show or go....

 

I just weighed my old 17" bullets and they weigh appox 53lbs each (wheel and tire),with an outer diameter of the tire coming in at 27.122 inches. I just installed 20" wheels just a couple of days ago and they weigh appox 53lbseach(wheel and tire)also with the outer diameter of the tire 27.027 inches. These numbers are based on 235/55R17 and 255/35R20 tires. So I guess it would all depend on the weight of the larger wheel, and what material it is made of. I cannot feel any difference in performance whatsoever, the speedometer is off a little bit at indicated 75mph the car is actuallymoving at74.58713602781398.

 

well thanks for the input everyone. i had a hunch that they do weigh a littlemore than the 16s. I shoulda weighed them before hand, didn't do enough research i guess.

 

It is also important to consider overall tire/wheel height. If your new combo has a taller height than what you started with, you will have reduced the engine rpm at a given speed. This has thesame effect as reducing your rear end gear ratio. Anytime you go to a larger wheel, you should go with an appropriate lower profile tire to maintain your overall gear aspectif, in fact, you want the effective gearing to remain unchanged.

 

in one of the mags, it showed that a person that had 20" rims lost 10rwhp just from weight and the amount extra just to turn them. i've heard that every inch in rim size you go you lost about 2-3 rwhp. also the bigger the tires or wider, they more weight.

 

Its rotational mass(weight),you can get some crossed drilled and slotted rotors to help even out the weight gain from the wheel and tire package.

 

1. Speedo error: Only the outside diameter of the tire affects your "gearing" and speedo error. Rim size (16, 17, 18, 19, 20, etc.) has nothing to do with this.

2. Larger rims are worse for acceleration even if the total package is the same weight as what you had before. Inertia is derived from the product of mass and radius. Larger wheels carry most of their weight at a larger radiust. For example, suppose your stock 17" wheel and tire package weighs in at 50 lbs. You switch to 20s, and suppose those also weigh 50 lbs. (which means very light 20s). The 20's have higher inertia than the 17s because even though the weight is the same, the 20" set carries that mass further out from the center of the wheel. In order for a 20" wheel & tire package to have a the same inertia as a smaller-wheel-diameter package, the 20" combo would have to be lighter, which is extremely unlikely.

3. Technically drilled brake rotors are lighter, so switching to them would save some weight. However it is a TINY bit of weight. I'd be suprised if it was more than 2 or 3 ounces per disc. The only truly effective way to save weight is to buy race-oriented wheels which are actually designed for light weight, not looks like most wheels are.

 

Great explanation.Thanks