Questions & Answers about שני הבלמים תקינים.
Because שני is the form used before a noun: שני הבלמים = the two brakes / both brakes.
שניים is usually used when two stands on its own, without a noun right after it.
- שני הבלמים = the two brakes
- שניים תקינים = two are working / two are fine
So in this sentence, שני is the correct form.
It can literally mean the two brakes, and in natural English that often becomes both brakes.
Because the noun is definite here (הבלמים = the brakes), the whole phrase is definite:
- שני בלמים = two brakes
- שני הבלמים = the two brakes / both brakes
So in this sentence, both brakes is a very natural translation.