die Radtour
bike tour
An outing or trip taken by bicycle.
Für den Sommer planen wir eine mehrtägige Radtour durch die Alpen.
For the summer, we're planning a multi-day bike tour through the Alps.

bike tour
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bike tour
An outing or trip taken by bicycle.
Für den Sommer planen wir eine mehrtägige Radtour durch die Alpen.
For the summer, we're planning a multi-day bike tour through the Alps.

'Die Radtour' (bike tour) is a compound noun made from 'das Rad' (short form for bicycle) and 'die Tour' (trip, outing). So it literally means a tour by bicycle.
Unsere erste gemeinsame Radtour war ein tolles Erlebnis.
Our first bike tour together was a great experience.
When talking about a bike tour, you usually use the verb 'machen' (to do / to take). A slightly more formal variant is 'unternehmen' (to undertake).
Am Sonntag machen wir eine Radtour mit der ganzen Familie.
On Sunday we're taking a bike tour with the whole family.
'Radtour' (bike tour) is often combined with adjectives that describe the duration or the route, for example 'eine kurze/lange Radtour' (a short/long bike tour), 'eine mehrtägige Radtour' (a multi-day bike tour), or 'eine gemütliche Radtour' (a relaxed bike tour).
Wir planen eine gemütliche Radtour am See.
We're planning a relaxed bike tour by the lake.
tour
'die Tour' and 'die Radtour' can both mean an outing or a longer route. 'Tour' is more general: you can be traveling on foot, by bike, by car, or by another means of transport. 'Radtour' is more precise and clearly says that you are going by bicycle. The words can be confused because a bike tour can always also be a tour. If the means of transport is important, 'Radtour' sounds more natural. If it is generally about the outing or the route, 'Tour' is enough.

Nach der Arbeit machen wir eine kurze Radtour am Fluss entlang.
After work, we are going on a short bike tour along the river.
Im Sommer planen meine Freunde eine Tour durch die Berge.
In the summer, my friends are planning a tour through the mountains.