My factory rim is 23 lbs and GSD tire is 24.1 lbs totaling 47.1 lbs.

I want to plus size to 18" rims. The rims I want weigh 26 lbs and the tires 24.5 lbs totaling 50.5 lbs.

What kind of performance (acceleration and braking) will the added 3.4 lb. difference on each corner of my car make? FYI, the overall diameter of the new setup will be 1.7% less, so there would be a performance gain from this.

Any ideas?

2004 Sedan 5AT STS
Huper Optik Ceramic 50/Underbody Diffusers/Clear Corners/Brake Cover
GroundingGear 7 Wire/Z-Tube/Stillen High Flow Airbox/HKS Sport Exhaust/Technosquare F-Spec ECU

 

Wheel and tire weight (sometimes referred to as rotational weight) has more effect on your car's performance when compared to static or dead weight (like the seats, chassis, etc.). I've heard/read that you should multiply rotational weight by anywhere from x2 to x7. The most common number I've seen is around x4 and that's the rule of thumb I use.

You also have to remember that more of the weight will be further away from the center of the wheel which will hurt performance.

Therefore, if you're adding 3.4 lbs per wheel and tire, you're effectively adding around ~54.4 lbs of dead weight. It's probably not going to affect your performance that much. If your G will do the 1/4 mile in 14 seconds (for argument's sake) you'll probably do the same in around 14.05 seconds if you subscribe to the theory that every 100 lbs. adds a 1/10 to your time.

As you can see, all of the above is not exact science but I think they're sufficient for our purposes.

When I had the sedan, I upgraded to 19" wheels that were about 5 lbs. heavier per corner. I didn't have the technical knowledge back then that I do now so it was more about looks. I did notice a slight drop in performance as the car felt a little more sluggish. When I did swap the wheels out back to stock when I sold the sedan, I noticed a difference in performance for the +. With that, I have upgraded my wheels and tires in my coupe now and they are 13 lbs. lighter than stock altogether.

If you're not that worried about performance, go with what looks good to you. If you are, you might want to look at some lighter weight alternatives.

I forgot about the reduced diamter issue. when you reduce the rolling diameter of the tires, you effectively increase the final drive ratio of your tranny. The higher the final drive, the better your acceleration, all other things being equal. However, I don't think you'll notice much if anything by decreasing the diameter by less than 2%. <P ID="edit"><FONT class="small"><EM>Edited by al503 on 10/01/04 02:03 PM.</EM></FONT></P>