A slip-on drive for the moun­tains

The RELO slip-on drive helps push the pedals when it gets hard for the cyclist. And it fits on every bike, whether moun­tain or city bike. The drive only provides as much assis­tance as the cyclist wants. To develop the trans­mis­sion, the experts from RELO and ebm-papst formed a tandem.


The bicycle drive weighs in at only  3.7  kilo­grams. The lithium-ion battery contributes 700 grams of that. It has a charging time of 45 minutes. The brush­less 250-watt motor weighs 1.3 kilo­grams and the trans­mis­sion, which is fixed to the bicycle, weighs 1.7 kilo­grams.

About RELO

Philipp Nagler had the idea of devel­oping a remov­able slip-on drive compat­ible with all bicy­cles. He began looking into the matter while he was still a univer­sity student. With three colleagues, he achieved his goal in the German town of Lauf. Now RELO is based in Nurem­berg, where over 30 employees work on ongoing devel­op­ment and produc­tion.

  • The bicycle drive has been in devel­op­ment since 2013. RELO has been producing and marketing its inge­nious drives since March of this year.
  • The name RELO is derived from that of the German engi­neer Franz Reuleaux, who did pioneering work in gear theory. The Reuleaux triangle looks like a normal triangle with rounded sides. The RELO experts designed the motor and the battery with this shape so more cells could be inte­grated.
  • The overall system is designed for long-term flex­i­bility. All future improve­ments will be compat­ible with the basic system and do not have to be constantly replaced.

Effi­cient trans­mis­sion

The trans­mis­sion needed to fulfill two main require­ments: it had to be compact and quiet. With the EtaCrown Wts5 crown gear­head from ebm-papst ZEITLAUF, the drive runs quietly and with an effi­ciency of 91 percent. The trans­mis­sion was specially tailored to this appli­ca­tion.

Perfectly connected

The cyclist selects the desired drive power level with the wire­less Blue­tooth thumb switch and is well connected with the RELO app that shows the speed, drive power level and battery level on a smart­phone. The app also takes care of soft­ware updates for the drive.

Fit for off-road and city

A magne­sium housing encloses the trans­mis­sion, making it both light and rugged. Whether the cyclist charges over rocky terrain or just makes the rounds in city traffic, the magne­sium housing is main­te­nance-free and meets all expec­ta­tions.

Spon­ta­neous deci­sion

Once the trans­mis­sion is mounted on the bike, it remains perma­nently attached to the frame. The motor and battery can be removed in no time and carried in a back­pack. The cyclist can decide on a whim whether to ride with or without the drive.

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