Cuanto más pedaleamos, más brilla la luz trasera.

Because here cuanto is not being used as a question word. It is part of the fixed comparative pattern:

cuanto más..., más... = the more..., the more...

Spanish uses cuánto with an accent in direct or indirect questions, such as:

• ¿Cuánto cuesta? = How much does it cost?
• No sé cuánto cuesta. = I don’t know how much it costs.

But in your sentence, cuanto is functioning as part of a comparison, so it has no accent.

It uses the correlative comparative pattern:

Cuanto más X, más Y
= The more X, the more Y

So:

• Cuanto más pedaleamos = The more we pedal
• más brilla la luz trasera = the more the rear light shines / the brighter the rear light shines

This structure is very common in Spanish. Similar examples:

• Cuanto más estudias, más aprendes.
• Cuanto más practico, mejor hablo.

Because the sentence is making a two-part comparison.

In English, we also repeat the comparative idea:

• The more we pedal, the more the rear light shines.

In Spanish, that repetition is also required:

• Cuanto más pedaleamos, más brilla la luz trasera.

The first más goes with the first clause, and the second más goes with the result clause.

Pedaleamos is the first person plural form of pedalear in the present indicative.

So it means:

• we pedal
• or sometimes we are pedaling, depending on context

Here it refers to we in a general sense: when we pedal more, the light shines more.

Breakdown:

• pedalear = to pedal
• pedaleamos = we pedal

Because the subject is la luz trasera, which is singular.

• la luz trasera = the rear light
• one light = singular
• therefore the verb is singular: brilla

So:

• la luz trasera brilla = the rear light shines

If the subject were plural, the verb would be plural too:

• las luces traseras brillan = the rear lights shine

Both are possible.

Spanish allows more flexibility in word order than English. In this sentence, putting the verb before the subject sounds natural:

• más brilla la luz trasera

You could also say:

• Cuanto más pedaleamos, más la luz trasera brilla

but that sounds less natural. A more natural alternative would be:

• Cuanto más pedaleamos, más brilla la luz trasera.

So the original wording is the most idiomatic.

Literally:

• luz = light
• trasera = rear / back

So la luz trasera means the rear light or the back light.

Trasera is the feminine singular form of trasero, and it agrees with luz, which is feminine:

• el asiento trasero = the rear seat
• la puerta trasera = the rear door
• la luz trasera = the rear light

Because Spanish often uses the present tense for general truths, regular relationships, and cause-and-effect statements.

This sentence expresses a general principle:

• when we pedal more, the rear light shines more

So the present tense is natural:

• Cuanto más pedaleamos, más brilla la luz trasera.

English does something similar:

• The more we pedal, the brighter the rear light gets.

It is not mainly about one specific future event; it is about how the system works in general.

The comma is standard and very helpful here because it separates the two linked parts of the comparison:

• Cuanto más pedaleamos, más brilla la luz trasera.

It is the normal way to write this structure. Even if you might sometimes see informal writing without it, using the comma is the best choice.

Yes, in much of Latin America, mientras más... is very common and natural in speech.

So these can both be heard:

• Cuanto más pedaleamos, más brilla la luz trasera.
• Mientras más pedaleamos, más brilla la luz trasera.

However, cuanto más... is often taught as the more standard or traditional form, and it works well everywhere in formal Spanish. For a learner, cuanto más... is an excellent form to know and use.

Not literally. The Spanish sentence says the more we pedal, not the faster we pedal.

• más here means more
• it does not specifically mean faster

That said, depending on the real-world situation, English might sometimes express the idea more naturally with faster if the context is about speed. But grammatically, the Spanish sentence is built on more, not directly on faster.

If you wanted to say the faster we pedal, Spanish would more directly use something like:

• Cuanto más rápido pedaleamos...

Yes. This pattern is very productive in Spanish.

With adjectives:

• Cuanto más difícil es, más interesante me parece.
• The more difficult it is, the more interesting it seems to me.

With adverbs:

• Cuanto más lentamente hablas, más te entiendo.
• The more slowly you speak, the more I understand you.

With verbs:

• Cuanto más lees, más aprendes.
• The more you read, the more you learn.

So your sentence is one example of a very useful structure you can reuse often.