Many technicians and users think that this bolt can simply be reused after disassembly.
However, that is not a good idea!
The bolt that secures the crank to the axle is often a so-called stretch bolt. This type of bolt is designed to stretch slightly during the first installation.
This creates the correct preload and keeps the crank firmly and safely in place on, for example, the Technogym Bike, New Bike, Lifefitness, and Matrix Home Trainers, Upright and Recumbent Bikes.
What is a tension bolt?
A stretch bolt is specifically designed to be under tension during installation. When tightened, the bolt is slightly stretched. That may sound strange, but this actually creates a very strong and reliable connection.
The downside is that after the initial installation, the bolt no longer has the same properties as a new bolt. Its elasticity and strength decrease because the material has been under permanent stress.
That is why manufacturers almost always recommend replacing the crank bolt as soon as it has been removed.
Why reusing it carries risks
When a used tension bolt is reinstalled, it often can no longer handle the load properly. The risk of material fatigue increases significantly.
This can lead to:
- Loose cranks
- Play in the axle
- Damage to the crank or bearings
- The bolt breaking during use
- Additional wear and tear on the fitness equipment
The biggest problem arises when the bolt actually breaks off. Because crankshaft bolts are usually made of hardened steel, they are extremely strong—but that also makes them difficult to remove when they break off inside the shaft.
Broken crankshaft bolt? That often means an expensive repair
In many cases, removing a broken crankshaft bolt is no easy task.
Because the bolt is made of hardened steel, it cannot be easily drilled out with a standard metal drill bit. Special carbide drill bits, extractors, or even professional workshop equipment are often required.
In some cases, the axle is also damaged, meaning that not only the bolt but the entire axle must be replaced.
A relatively inexpensive new crankshaft bolt set can therefore ultimately prevent an expensive repair.
When should you replace the crank bolt?
We recommend always replacing the crank bolt when:
- The crank has been disassembled
- Bearings or the bottom bracket are being replaced
- Maintenance has been performed on the drivetrain
- The bolt is visibly damaged
- The bolt has been used previously
Safety and reliability come first
In fitness equipment, parts are often subjected to heavy loads. Especially on spinning bikes, indoor cycles, and professional upright bikes and home trainers, enormous forces act on the crank assembly.
Proper installation with new fasteners is therefore essential for:
- Safe training
- Long service life of parts
- Reduced risk of malfunctions
- Reliable operation of the equipment
Order the right crankshaft bolt right away
Are you replacing a crankshaft or bearings? Don’t forget to order a new crankshaft bolt at the same time.
A small investment prevents major problems and ensures that your fitness equipment continues to operate safely and reliably.
Browse our selection and order that set of new crankshaft bolts today!
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