mis3

I checked the 2004 CLK brochure and I saw the following:

1. CLK500
225/45ZR17, front
245/40ZR17, rear

2. CLK55
225/45ZR17 91Y, front
245/40ZR17 91Y, rear

What is 91Y?

scorchie

91 = load range/index
Y = speed rating

-s-

MBToGoNow

The Z speed rating tells you that the tire is capable of sustained speeds in excess of 240km/hr (149mph), but it doesn't tell you how much above 149mph. Thus, knowing that a tire is Z-rated is not specific enough. You need the "Y", which is the specific speed rating and tells you that the top sustainable speed for that tire is 300km/hr (186mph). An Z-rated tire can either be V-Rated (240km/hr), W-Rated (270km/hr or 168mph) or Y-rated.

So, in the CLK55, the "Z" in "225/45ZR17 91Y" is redundant if you know it's a "Y" because a "Y" is always a "Z" (but not the other way around).

The "91" is the load index signifying the load carrying capacity and 91 means a load capacity of 615Kg (1,356lbs).