Wir montieren das Rad ab.

Because the full verb is abmontieren, which is a separable verb.

In a normal main clause, the conjugated part goes in the usual verb position, and the prefix moves to the end:

• abmontieren → Wir montieren das Rad ab.

This is very common in German:

• Ich rufe dich an. = anrufen
• Sie macht das Fenster auf. = aufmachen

When the verb is not split, the parts stay together:

• Wir wollen das Rad abmontieren.
• Das Rad abzumontieren ist schwer.

The dictionary form is abmontieren.

In this sentence, it appears split up:

• Wir = we
• montieren = the conjugated verb part
• ab = the separated prefix

So if you look it up in a dictionary, you would usually search for abmontieren, not just montieren.

montieren usually means to mount, install, assemble, fit.

Adding ab- often gives the idea of removing, taking off, or dismantling from something.

So:

• montieren = to mount / install
• abmontieren = to remove / take off / dismantle

A useful pair is:

• Wir montieren das Rad an. = We attach the wheel.
• Wir montieren das Rad ab. = We remove the wheel.

Because Rad is a neuter noun, so its article in the nominative and accusative singular is das.

Here it is the direct object of the verb, so the accusative is needed:

• nominative: das Rad
• accusative: das Rad

Since neuter singular does not change in the accusative, it still looks like das Rad.

Compare with a masculine noun, where you would see the accusative change:

• der Reifen → den Reifen

Wir is the subject because it is the pronoun meaning we, and it matches the verb form montieren.

German subjects and verbs agree:

• ich montiere
• du montierst
• wir montieren

So wir montieren clearly means we remove/install.

German main clauses usually follow the verb-second rule, often called V2.

That means the finite verb goes in the second position of the clause:

• Wir montieren das Rad ab.

Here, Wir is in the first position, and montieren is in the second.

If something else comes first, the verb still stays second:

• Heute montieren wir das Rad ab.
• In der Werkstatt montieren wir das Rad ab.

So the subject does not always have to come first, but the finite verb usually stays second.

No, not in a normal main clause.

Because abmontieren is separable, you normally must split it:

• Wir montieren das Rad ab. ✅

Not:

• Wir abmontieren das Rad. ❌

But the unsplit form appears in other structures, for example:

• Wir wollen das Rad abmontieren.
• Das Rad wurde abmontiert.
• Das Abmontieren des Rads dauert lange.

Yes, especially in technical, mechanical, or practical contexts.

It sounds natural when talking about removing something that has been attached or installed, such as:

• a wheel
• a shelf
• a lamp
• a machine part

Depending on context, German speakers might also use other verbs such as:

• abnehmen = take off
• entfernen = remove
• demontieren = dismantle / take apart
• abbauen = dismantle / take down

But abmontieren is a very normal choice when something is mounted and then removed.

By itself, Rad can mean different things depending on context, including:

• wheel
• bicycle in some contexts
• part of a machine or vehicle

In a sentence like Wir montieren das Rad ab, it most naturally means the wheel, because removing a whole bicycle would not usually be expressed that way.

So context tells you which meaning is intended.

Yes, but it would mean something different.

• Wir montieren das Rad. = We mount/install/assemble the wheel.
• Wir montieren das Rad ab. = We remove the wheel.

So ab is essential here. It changes the action from putting on / assembling to taking off / removing.

It is in the present tense: Präsens.

• Wir montieren das Rad ab.

In German, the present tense is often used not only for what is happening now, but also for planned or near-future actions, depending on context.

For example, this could mean:

• We are removing the wheel.
• We remove the wheel.
• We’ll remove the wheel.
  (if the context makes that clear)

Here is the present tense of abmontieren in a main clause:

• ich montiere ... ab
• du montierst ... ab
• er/sie/es montiert ... ab
• wir montieren ... ab
• ihr montiert ... ab
• sie/Sie montieren ... ab

Examples:

• Ich montiere das Rad ab.
• Du montierst das Rad ab.
• Er montiert das Rad ab.

This helps you recognize that montieren in your sentence matches wir.

Not especially in this sentence. Das Rad is the direct object, and it comes between the conjugated verb and the separated prefix:

• Wir | montieren | das Rad | ab

That is a very typical pattern with separable verbs.

You can move things around for emphasis, but the separated prefix normally stays at the end in a main clause:

• Das Rad montieren wir ab.
• Heute montieren wir das Rad ab.

So the object position here is normal and neutral.

In a subordinate clause, the separable verb is usually not split. The full verb goes to the end:

• ..., weil wir das Rad abmontieren.

Compare:

• Main clause: Wir montieren das Rad ab.
• Subordinate clause: ..., weil wir das Rad abmontieren.

This is an important pattern in German:

• main clause → separable verb splits
• subordinate clause → separable verb stays together