In general, you have a statutory warranty of 2 years.
This is to ensure that the goods are free of defects of quality and free of defects of title at the time of delivery.
Should there be a defect within the first 2 years you can demand rectification:
Is the rectification you demand associated with disproportionately high costs bike-discount.de can reject it and choose one of the other two options of rectification.
Within the first 6 months after delivery of the goods it is assumed that a defect is a concealed defect.
Excluded from this are damages caused by external influences or normal abrasion. After these 6 months, the so-called reversal of the burden of proof takes place.
After the first 6 months you have to proof, that the item had a concealed defect already with the delivery when the defect has occurred afterwards.
The statutory warranty is no durability guarantee. In particular the warranty does not cover damage caused by external influences (e.g. crashes) or normal abrasion (e.g. tires, brake pads etc.).