Learn Danish: En nok så dyr racercykel skal vel smøres? - Even the most expensive racing bike needs to be lubricated, right?

The phrase nok så followed by an adjective creates a concessive meaning, translating roughly to "however [adjective]" or "no matter how [adjective]". So, en nok så dyr racercykel literally means "a however expensive racing bike". In natural English, we usually express this idea as "even the most expensive racing bike".

What is the exact purpose of vel in this sentence?

vel is a modal particle showing that the speaker assumes a statement is true and expects the listener to agree. It does not translate to a single direct word, but in English, we often capture its feeling by adding a tag question like "right?", "don't you think?", or starting the sentence with "surely".

Why does the verb smøre have an -s at the end here?

The -s makes it a passive infinitive (the s-passive). Because the subject of the sentence is the bike, it isn't doing the lubricating—it is receiving the action. Following the modal verb skal (must or needs to), we use the passive infinitive smøres to mean "to be lubricated".

Could I say selv den dyreste racercykel instead of en nok så dyr racercykel?

Yes, absolutely. selv den dyreste racercykel is a more direct, literal translation of "even the most expensive racing bike". The construction en nok så dyr is an idiomatic and slightly more formal way to express the exact same concept in Danish.