Amin Skaf

Hello everyone,

I'm seriously a newbie when it comes to car-related upgrades. I had a few questions regarding tire/rims upgrades.

From researching the forum and the net, I realize that upgrading the wheel will result in a larger tire, unless one chooses to get a smaller profile tire. The larger the tire, the bigger discrepancy on the speedometer.

My questions are this:

The owner's manual states that the C-Class can be equipped with 17, 18, and 19 inch rims. But they state that the c250/300/350 have a max of 18 while the c63 can have the 19s. My question is this: What does the car detect? If it's a c250/350 does it auto adjust for the Mercedes recommended tires/wheels for 18 inches but wont for 19 unless it's a c63?

I am thinking about getting C63 replica AMG 19 inch rims for my car and want to make sure that the car can adjust as necessary. Reading the owner's manual, I couldn't find anywhere that stated where options were in COMAND to address some of these changes.

Thank you for the help!

andrew e coupe

The overall diameter of an upsized rim and tire combination should retain the same overall height/diameter if done correctly ... (a larger rim = a smaller side wall) ... hence having no impact on the speedometer maintaining the exact factory readings.

I am running 19" wheels on my C250 and the speedo is dead on (tested at varying speeds through a police officer friend via laser radar).

Hope this helps.

Amin Skaf

Nice wheels Andrew!

Thank you for the reply. So now my question is what is considered 'factory'. Does the car measure the deviation from the rims that came with the car or do I have options to plug into the car based on the 17, 18, and 19 inch factory rims for the C204?

VIPCHOI

use the calculator on top of the forum

http://www.e90post.com/forums/showthread.php?t=400004

all the wheel and tires specs are in your owner's manual

Amin Skaf

Does COMAND have a setting to indicate which 'factory' option is equipped?

Amin Skaf

I guess my question is does my car have multiple factory settings that I can change for wheels/tires or is that unchagable and any deviation will be based on the particular wheels/tires that came with my car. I would assume since Mercedes themselves offers 18 inch rims for my vehicle that that could be easily done without having the speedo off. Is there a setting in the computer that a consumer can access or only someone w/ access to STAR diagnostics?

RY213

You are not understanding what people are telling you. There is no change to the overall diameter of the tire and wheel when you go to a bigger wheel, so there is no need to make adjustments to the speedometer.

17" wheel + 3" tire sidewall = 20"
18" wheel + 2" tire sidewall = 20"
19" wheel + 1" tire sidewall = 20"

andrew e coupe

~ there is no way to reconfigure the factory settings to the speedo mph per the wheels size for they are fixed per the manufacture and should remain constant.