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.

1. Remove left crank

2. Fasten gearbox housing to down tube with three metal strips

3. Insert gearbox

4. Replace left crank

5. Ready to ride

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