Krzysiu, I doubt you have 'R' speed rated tyres. Looks you got 18" wheels?
You probably saw something like 235/40/R18. In this case the R stands for Radial, the tyre's internal construction.
These days the speed rating is shown after this, along with the load rating.
For example 235/40R18 93W. Where the 93 is the load rating, W is the speed rating.
In the past the speed rating was shown within the tyre size. eg 235/45ZR17, like blind_elk said. Maybe some tyre manufacturers still do it this way.
http://www.tirerack.com/tires/tiretech/gen...neral/speed.jsp