Frequently asked questions:

What is Gruber Assist?
Gruber Assist is an auxiliary drive for bicycles, which has a direct effect on the crank. The auxiliary drive is designed to provide assistance and not self-propelling.

What does my bicycle need in order to retrofit a Gruber motor?
- Frame (we didn’t test carbon adequate yet)
- Straight, continuous seat tube
- Seat tube with an inner diameter of 31.6mm
(This is given for a seat post with an outer diameter of 31.6mm)
- The existing seat post will be replaced with a Truvativ XR double clamp (included in delivery)
- Crankset from Shimano Hollowtech II
- Seat tube should be as central as possible on the bottom bracket (not shifted forwards or backwards!)

A minimum diameter of 31.6mm is required for the seat post. Cycles for which this is the case:
Models from Ghost, Trek, Maxx, Cube, Simplon, Cannondale, Canyon, Steppenwolf, Stevens, Storck, Focus, Scott, Alu Tech, Bergamont, Centurion, Red Bull, Fuji, Hai, Hot Chili, Cheyenne, Drössiger, FAT, …

How can I get an idea of what the 100-watt performance increase will be like?
The simplest way is to try to pedal to approx. 150 watts on the ergometer. After about 10 minutes, slow down to 50 watts – can you notice the difference? Another way to imagine it is as if another person were pushing your bike from behind.

Can I also install the motor into trekking or tour cycles?
Yes, provided that the specifications (see above) are met!

Is there a throttle control?
No, there is only an on/off switch. However, it is also possible to programme the number of pedal rotations (that is the speed at which the motor powers the pedals) at any time. In the process, it is also possible to simply push the bicycle at your side with a very low number of pedal rotations.

How long does the service live of the battery last?
500 recharging cycles (NiMH), 800 recharging cycles (LiION)

How long does it take to charge the battery?
The charging process takes a max. of 3 hours, depending on how discharged the battery was.

Do I have to discharge the battery fully before I can recharge it?
The battery must not be fully discharged each time before it can be recharged.

Does the battery recharge itself when cycling downhill or by pedalling hard?
No.

How long can I cycle with one battery?
The NiMH battery lasts for at least 45 minutes at full throttle. By pedalling hard, the capacity can be extended to a max. of 1:30 hours.
The LiION Mangan battery lasts for at least 55 minutes at full throttle. By pedalling hard, the capacity can be extended to a max. of 1:45 hours.

Is a replacement battery included in delivery?
No, a replacement battery is not included in delivery. This can, however, be ordered additionally if desired.

What is included in delivery?
The following is included in delivery: the propulsion unit, the bar ends, the seat post, the saddlebag, the battery and the battery charger.

What must be modified on the bicycle to install the motor?
The seat tube must be internally drilled out with a reamer. Bottle mounts are thereby separated from the seat tube. Using an M4 drill, the seat tube is drilled from the outside, approx. 7cm above the bottom bracket, for two mounting screws. It only in this way certain that the drive pinions are held at the correct distance.

How long does the installation take?
Approx. 1.5 hours.

Can I carry out the installation myself?
A special tool is required for the installation. Therefore, only an installation by an authorised specialist dealer is possible.

The drive does not support me, what can I do?
Most likely only a too small number of revolutions of the pedals/min. is stored.
This you can change, by pushing the on-/off-button for 5 seconds and pedaling as fast as possible.
Thus you store a new pedal frequnecy and get supported by GRUBER Assist, if you slow down.
For switching on and off a short activation of the function push-button is enough.