This is the 10999th most frequent Polish word.
felgach
"Felgach" is the locative plural form of "felga," meaning "rims" (of a wheel).
Here, "felgach" refers to 'rims', part of a set of parts belonging to the wheels of a car. It is used in the plural form in the locative case to indicate location or on what the car 'looks great'.
Samochód wygląda świetnie na nowych felgach.
The car looks great on the new rims.
In this sentence, "felgach" retains its meaning of 'rims' and is used to describe the object related to the action of 'checking the condition' which involves tires in 'state' on the rims.
Zawsze sprawdzam stan opon na felgach przed podróżą.
I always check the condition of the tires on the rims before a journey.
Here, "felgach" is again used in plural locative form to specify the object 'rims' related to the mechanic's action of removing tires from them.