Learn Hardcore Japanese: hensokuki wo kurabe, hensokudansuu wo kakuninsita sueni, kurosubaiku wo eranda. - After comparing the gear systems and checking the number of gears, I chose a cross bike.

Breakdown of hensokuki o kurabe, hensokudansuu o kakuninshita sueni, kurosubaiku o eranda.

How is this sentence read?

A natural reading is:

へんそくきをくらべ、へんそくだんすうをかくにんしたすえに、クロスバイクをえらんだ。

Word readings:

Why are there spaces between the words? Is that normal Japanese?

No. Normal Japanese is usually written without spaces:

変速機を比べ、変速段数を確認した末に、クロスバイクを選んだ。

The spaces in your example were probably added just to make it easier for learners to see the parts of the sentence.

What is the basic structure of this sentence?

The sentence breaks down like this:

変速機を比べ、
= comparing the gear systems,

変速段数を確認した末に、
= after checking the number of gears / after going through that process,

クロスバイクを選んだ。
= chose a cross bike.

So the main action is 選んだ. Everything before it explains the process that led to that choice.

Why is it 比べ and not ?