Rims size, change in performance Options

[gnetik]

hey guys, I was just wondering, how much difference would you feel between using stock 15 inch rims and 17 inch rims (not chrome or lightweight performance) such as the adr gt sports? Anybody who switched from stocks to 17 inchers, please tell me what difference you felt (how much slower). Also, anybody with track experience, what is the difference in quarter mile from stock 15 inchers and 17 inchers? Anybody with input please........uh.. input? haha! yeah, well thanks! (sorry if this is stupid question)

[94GT]

Here is the bottom line: Your performance will suffer if you switch from 15's to 17's. When you displace the mass of the very outside of your rim from 7.5 inches (15's) to 8.5 inches (17's) from the center of the hub, it requires your car to work harder to rotate the wheel. (I don't remember the equation, so I can't tell you how much since I brain dumped all that after college...) Another area of concern which has prevented me from upgrading my wheels, is that if you calculate the sidewall height, I have not been able to find a rim and sidewall height that exactly matches the total diameter of my current 15's (with tires mounted). They all go up by a bit. This will change your speedometer anywhere from 5 to 10% depending on what you do. A lot of people upgrade their wheels, and I haven't yet heard of anyone having their speedometer recalibrated, so people who have done that are slightly off on their speedometer and odometer. You're actually going slightly faster, and slightly farther than indicated on your gauge. Until I find a mechanic who can recalibrate my speedometer when I upgrade the wheels, I'm just going to stick with the stock 15's. Anyone ever have that done?

[Mr_E]

Here is the bottom line:  Your performance will suffer if you switch from 15's to 17's.  When you displace the mass of the very outside of your rim from 7.5 inches (15's) to 8.5 inches (17's) from the center of the hub, it requires your car to work harder to rotate the wheel.

You're assuming that the rim is heavier than the tyre.

(You're correct)

However, bigger rims means less sidewall flex. This is a good thing.