Plášť je na ráfku.

Yes, plášť can mean coat, cloak, covering, or outer layer in different contexts. In bicycle or wheel vocabulary, plášť commonly means the tire (more precisely, the outer tire casing).

So in this sentence, plášť is not clothing. It is the tire mounted on the wheel.

Because na here means on in the sense of location, and with that meaning it takes the locative case.

• dictionary form: ráfek = rim
• locative singular: ráfku
• so: na ráfku = on the rim

This is a very common pattern in Czech:

• na stole = on the table
• na kole = on the bicycle / on the wheel
• na ráfku = on the rim

If na expresses movement toward something, it can take the accusative instead, but here the sentence describes a state, not motion.

Ráfku is the locative singular of ráfek.

The preposition na often requires:

• locative for location: on
• accusative for direction: onto

Here it is location, so Czech uses the locative:

• Plášť je na ráfku. = The tire is on the rim.

Czech uses na because the tire is understood as being on / mounted on the rim.

• na ráfku = on the rim
• v ráfku would mean something more like in the rim, which is not the normal way to describe a tire’s position

So na is the natural preposition for something attached to or resting on a surface or support.

Je is the 3rd person singular present tense of být = to be.

So:

• plášť = tire
• je = is
• na ráfku = on the rim

Together:

• Plášť je na ráfku. = The tire is on the rim.

Unlike in some languages, Czech normally keeps this present-tense form of to be in a sentence like this.

Yes. Czech word order is more flexible than English word order.

The neutral order here is:

• Plášť je na ráfku.

But you could also hear:

• Na ráfku je plášť.

Both are grammatical. The difference is mainly one of emphasis or information structure.

• Plášť je na ráfku. → neutral, starts with the tire
• Na ráfku je plášť. → emphasizes where it is

English usually has to keep a stricter order, but Czech can move elements around more freely.

Both plášť and ráfek are masculine inanimate nouns.

That matters because adjectives, pronouns, and sometimes numerals will agree with them.

For example:

• ten plášť = that tire
• ten ráfek = that rim

Their forms in other cases will also follow masculine inanimate patterns.

A rough pronunciation guide:

• Plášť: the á is long, and the end šť is a soft cluster that English speakers may find tricky
• je: roughly like ye
• na: like nah
• ráfku: long rá, then fku

A rough English-style approximation would be:

• PLAASHT yeh nah RAAF-koo

A few key points:

• á is long
• š sounds like sh
• ť is a softened t
• stress in Czech normally falls on the first syllable of each word

So:

• PLÁŠŤ je na RÁFku

Not always.

In everyday Czech, both can refer to a tire, but there is a nuance:

• pneumatika is a general word for tire
• plášť often refers specifically to the outer tire on a bicycle wheel

In cycling contexts, plášť is very natural. If the sentence is about a bicycle wheel, this word makes perfect sense.

The simplest way is just to change the intonation:

• Plášť je na ráfku? = Is the tire on the rim?

You can also put je first:

• Je plášť na ráfku?

Both are possible, and the second one is especially clear for learners because it matches the English idea of inversion.

You replace je with není:

• Plášť není na ráfku. = The tire is not on the rim.

This is the normal negative form of být in the 3rd person singular:

• je = is
• není = is not

No. Czech has no articles like a, an, or the.

So Plášť je na ráfku can mean:

• The tire is on the rim
• A tire is on the rim

Which one sounds best in English depends on context, but Czech does not mark that difference with an article.

It describes a state: the tire is on the rim.

There is no motion here. That is another reason why na takes the locative:

• na ráfku = on the rim, already there

If you wanted to describe motion, you would use a different structure, for example something like nasadit plášť na ráfek = to put / mount the tire onto the rim, where na ráfek would use the accusative because it shows direction.