Mike leroy
Active Member
I'm considering buying the Focus Aventura Speed Impulse, too. I wish it was priced more competitively, but I guess with all those premium components (carbon drive, etc), it's probably worth it. I can't stand riding an ebike with a traditional chain and derailleur (2015 IZIP E3 Dash). My chain hops off the front crank twice a week – how hard can it be to design a single-crank system where the chain doesn't hop off constantly?! Gates Carbon Drive + mid-drive is the way to go.
Bosch motor owners take note:
"... high performance use, the bicycle chain receives up to 500kg of force. Therefore, an extremely high level of surface pressure of 300kg/mm2 is to be found here within the chain links.
The smaller the chainrings are up front, the greater the amount of force is which is applied to the chain and with it, the amount of surface pressure applied to each individual chain link (e.g. all MTBs running compact drive, microdrive, and hyperdrive C). The amount of surface pressure also increases when the chain is running at an angle because the contact area is proportionately reduced. [more front/rear gear alignment difference, the larger the angle]."
Put this into perspective with a conventional mountain bike. The Santa Cruz Heckler, for example, uses Sram S1000 2x10 22/34 crankset. The Bosch has 16 teeth, or 25% fewer teeth than the 22 tooth Heckler.
What is the front/rear teeth ratio on your bike? Something like Haibike XDuro is 16 / 36 = 0.44. You might want to understand why Rohloff makes such a strong warning. I do not know or care, but it is a very serious issue to Rohloff. All I care about is Rohloff telling me I need at least 34 teeth on the front chainring. 16 teeth on the Bosch has always seemed nuts to me. My first impression was the Bosch motor is a toy. I just laughed at it. Must be for a kid, not an adult. I could care less whether the motor gets 2.5 times reduction or not. I never accepted that small front sprocket. The front sprocket still humors me. Minaturation is an electronics goal, but not necessarily a mechanical one. I never heard Bosch made bikes. Bosch über shot the mark.
The higher the chainring/sprocket ratio, the lower the input torque to the gear-unit. It is imperative therefore that the chainring/sprocket factor does not drop below 1.9 (e.g. 34/17=2.0). The smallest permissible sprocket ratios for a rider weighing less than 100kg are: 32:17, 30:16, 28:15 and 26:13.
Have dropped chains been reported with IGHs? Carbon belts are generally less durable than chains. The primary benefit is noise reduction. I am ordering a Rohloff-14 IGH.
Seems like you something similar to: http://www.rohloff.de
Have you closely examined each link in the chain? If the chain pops on a consistent basis, something predictable is causing the problem. Search Google images for twisted chains. You will see slight chain deformations in the pictures. Not rocket science.
Might want to see how seriously Germans take chains. And their tools:
http://www.rohloff.de - The tool will indicate when the individual sprockets are on the verge of needing replacement, thus preventing chain skipping.
http://www.rohloff.de
The Rohloff Caliber 2 is a precision made chain wear indicator. It allows the measure of chain wear in seconds and indicates if the chain is too worn for steel or aluminum sprockets/chainrings. After extended use, a chain will no longer fit correctly in the teeth of the sprockets, due to elongation and wear. If the chain is not replaced, then chainrings and sprockets may be damaged, and eventually, the chain will skip over the sprockets. The Caliber 2 allows you to quickly determine chain wear before your chain gets to this condition.
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