When searching recumbent exercise bikes you probably noticed that they talk about the crank in some listings. (Not all do.)
The cranks are where the pedals screw into the bike. The parts the pedals are screwed into are called the arms or pedal shafts.
Those that do describe it is as a single crank or 3 piece crank. This is probably not as important as it is in spin bikes where you are standing on the pedals and really pushing hard against them and jumping on the pedals too . But can offer a better and stronger platform.
The crank is made up of the arms that the pedals screw into, the spindle that join them and they move to turn the drive and flywheel.
Much of this is enclosed in the shroud so aren’t actually seen by the user at all. Hopefully, there is never a need to look at them either. They do tend to be trouble free for the majority of users until the end of the life of the bike in a few years time.
The crank, if mentioned. is normally just mentioned and then you don’t get told what it means to you the user.
So, what are they…
1 Piece Crank
As the name suggests the arms and spindle are all made in one piece. The thread used to attach the pedals to the arms is 1/2 inch.
3 Piece Crank
As you might have guessed these are made of three pieces – 2 arms and spindle. The thread used to attach the arms is 9/16 inch. These are considered to be tougher and more durable than the 1 piece.
In outdoor bikes a 1 piece crank is usually used for kids bikes and some lower end adult bikes. The 3 piece cranks because they are tougher and lighter are used on most adult bikes these days.
How About Recumbent Exercise Bikes
Many recumbent exercise bikes use the 1 piece crank – in particular the more affordable priced bikes. On these bikes the resistance only goes up to moderately tough so you don’t have to push that hard relatively, you’re not going to be standing on the bike and probably only have a moderate intensity workout.
They seem to be tough for most people who buy these bikes like the popular and highly rated Exerpeutic 900XL. There are not any reports of issues with the crank breaking or bending. Or the pedals breaking off for that matter when properly attached during assembly.
More expensive bikes tend to have 3 piece cranks as these cranks are more expensive to manufacture. Also these bikes do provide you with harder resistance to push against so there can be more force in pushing against the pedals and supported by the crank -an example of a bike with a 3 piece crank is the Schwinn 270. (It cheaper version the Schwinn 230 has one piece crank but the same amount of resistance adjustment). You can put more force on it but again it is unlikely you will be able to generate the force used on a spin bike or outdoor bike.
Again these bikes (Schwinn 230 or 270) do not have a history of pedals or cranks breaking when properly assembled or manufactured.
For most people the difference between these type of cranks won’t play a part in their decision of buying a recumbent exercise bike as they aren’t interested in very challenging hill climb type workouts so a 1 piece crank is likely to more than enough.
However, if you want to be challenging yourself against resistance that is extremely tough then it becomes more important to get a more durable and tougher 3 piece crank (they can be easier to replace too if one of arms does break).