بطانة المكابح قرب محور العجلة.

It is very natural as a label, caption, or technical note. Arabic often uses short noun-based expressions in diagrams and manuals where English might also use a fragment.

It can still be understood as a complete idea: The brake lining is near the wheel axle.

If you wanted a more explicit everyday-style sentence, you could say:

• بطانة المكابح قريبة من محور العجلة
• تقع بطانة المكابح قرب محور العجلة

So the original wording is concise and technical.

Because بطانة المكابح is an iḍāfa construction, often called the construct phrase.

In an iḍāfa:

• the first noun normally does not take الـ
• the second noun determines whether the whole phrase is definite

So:

• بطانة = lining
• المكابح = the brakes

Together:

• بطانة المكابح = the brake lining / lining of the brakes

Since المكابح is definite, the whole phrase becomes definite.

For the same reason: it is the first word in an iḍāfa.

The first noun in an iḍāfa:

• does not take الـ
• does not take tanwīn

So you do not say بطانةٌ المكابح.

Instead, you say:

• بطانةُ المكابحِ in full formal vocalization
• or simply بطانة المكابح in normal unvocalized writing

المكابح is the plural of مِكْبَح, and in context it means brakes.

This is very natural, because Arabic often refers to the braking system in the plural, just as English does with the brakes.

So:

• مكبح = a brake
• المكابح = the brakes

Therefore:

• بطانة المكابح literally means the lining of the brakes

قرب here means near and functions as a word of location.

It is very common in MSA, especially in formal or technical language.

Grammatically, قرب often behaves like a noun in an iḍāfa-like structure:

• قربَ محورِ العجلةِ = near the wheel axle

So the noun after قرب is in the genitive.

In fully vocalized formal Arabic, قرب is often read as قربَ because it functions as a ظرف مكان, a locative adverb.

Both are correct, but they have different styles.

• قرب محور العجلة is shorter, tighter, and very common in manuals, labels, and technical descriptions
• قريبة من محور العجلة sounds more like a full descriptive sentence in ordinary prose

Since بطانة is feminine singular, قريبة would agree with it grammatically:

• بطانة المكابح قريبة من محور العجلة

But the original sentence prefers the more compact technical style.

It is another iḍāfa.

• محور = axis, axle, pivot
• العجلة = the wheel

So:

• محور العجلة = the wheel’s axle / the axle of the wheel

In automotive context, axle is the most likely meaning.

Just like in بطانة المكابح, the first noun:

• does not take الـ
• is linked directly to the second noun

Because بطانة is connected to another word in an iḍāfa.

A tāʾ marbūṭa is usually pronounced:

• as -a / -ah when stopping at the word
• as -t when the word is grammatically connected to what follows

So:

• by itself: بطانة ≈ biṭāna
• in this phrase: بطانة المكابح ≈ biṭānat al-makābiḥ

This is a very common point for learners.

A learner-friendly pronunciation in pause form is:

biṭānat al-makābiḥ qurb miḥwar al-ʿajala

If you read it in fully formal MSA with case endings, it would be closer to:

biṭānatu l-makābiḥi qurba miḥwari l-ʿajalati

In everyday educated pronunciation, many speakers reduce or drop the full case endings, especially outside very formal reading.

A fully vocalized version would be:

بِطانَةُ الْمَكَابِحِ قُرْبَ مِحْوَرِ الْعَجَلَةِ

Here is the breakdown:

• بِطانَةُ: nominative, if understood as the topic/subject
• الْمَكَابِحِ: genitive, because it is the second term of the iḍāfa
• قُرْبَ: accusative, because it functions as a locative adverb
• مِحْوَرِ: genitive, because it follows قرب in an iḍāfa-like relation
• الْعَجَلَةِ: genitive, because it is the second term in محور العجلة

In normal printed Arabic without vowel marks, learners usually focus first on recognizing the two iḍāfas:

• بطانة المكابح
• محور العجلة