dan212

I was thinking of change from 17 inch AMG to 18 inch AMG's on my CLK550. The larger AMG wheels - according to factory spec - will give me 255 rears instead of 245's. The front wheels stay 225 according to factory spec. I am burning rubber on launch so I think wider rears should help, but that is not my sole reason. This is for performance only and not looks. The car fish tails under hard full throttle at launch or on slow corners.

My dealer is recommending 18's that keep the 225 front but change the rear from 245 to 255.

questions:

Will the change to larger diameter wheels improve handling? How? Their may be a slight change in wheel weight - depends on the wheel I choose

Will the slightly wider rears in addition to the additional rubber from the change from 17 to 18 improve wheel spin?

SHOULD I be looking to increase front tires from 225 to 235? Won't that effect steering?

I don't want to cram the largest tires possible under the car for the sake of looks. I only want to improve handling. A slight change in ride comfort is OK.

Should I go to 19's or is this more for looks?

What are the negatives? Trying to understand the physics.

- dan

chixdiggit

Hi Dan,

I too am looking at purchasing rims and from what I've learned is that usually with larger diameter rims you are able to use wider tires. Wider tires will allow for better traction and thus better grip. Wheels also come in different widths for each size. Generally most of the stock rims are all one size on the vehicle (which allows you to rotate the wheels). Keep in mind that in theory when you increase the width of the wheels, friction also increases as well. The resistance and the increase weight of the rims can (potentially) increase the effort required for the vehicle to maintain it's speed, and exceleration. I'm not sure how big of an impact it will make seeing you have a V8 under the hood. The changes could be quite subtle and not noticeable.

The price for the tires seems to increase a lot more when you increase the wheel size past the 18" mark. Also with the increase of rim sizes, the tires themselves will have a lower profile which means the walls of the tires will be shorter. If you look and compare the tires for 17", 18" and 19" rims, you will notice the side profile of the tires become increasingly smaller and smaller resembling an rubber band stretched over the rims. This will also change the characteristics of a car's handling. As you increase the wheel sizes bumps and potholes in the street will feel more prominant and thus the comfort level of the ride diminishes; the benefit is better traction and handling.

Since you're increasing from 17 to 18 the changes and benefits will be subtle. A one inch change in diameter is not a significant change. 18" is the standard these days although 19"s are increasingly becoming the new 18"s. The price difference between 18" and 19" can be a few hundred dollars (my guess is about $500 - $800 difference including and depending on the rubber). Sure 19"s do look nice but it's not just for aesthetic reasons either. If you don't mind sacrificing comfort for additional speed around turns and corners and there aren't alot of potholes or speed bumps you could go with the 19"s.

As for the fishtailling issue; if you let up on the gas peddle it should reduce the amount of fishtailliing....

This is coming from what I understand regarding the dynamics of wheels. If anybody out there thinks otherwise feel free to correct me.

Hope this helped.

Nate