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<blockquote data-quote="mlx john" data-source="post: 9771" data-attributes="member: 1304">It's a known issue with these motors.The following is Bosch's offical response, but if you don't want to read the whole thing, in summary they're saying &quot;oh well, tough sh*t&quot;.&quot;When riding an eBike/eMTB on rough and technical terrain downhill, vibrations of the chain/chainring often occur. Those vibrations can be transferred to the frame, the drive unit and to the inner gear wheel (inside the drive unit). In some cases when freewheeling, a metallic sound can be generated when the inner gear wheel is not under load. How much vibration and sound is transferred depends on the type of bike (for example hardtail vs full suspension and aluminum vs carbon).The current Performance Line CX is designed with high power density and thermal stability as well as a highly efficient gearing mechanism and incredibly smooth-running gears. Paired with reduced weight, lower wall thickness and improved heat release it is easier for mechanical noises to be omitted. Therefore the noise may sound a little more prominent when compared with other drives. This noise does not have any influence on the performance, functionality or reliability of the motor. Usually an eMTB also makes several other noises as it navigates these technical sections of trail (tyres gripping/skidding, chain slapping etc) and thus any noises from the motor are drowned out.On further request: We would also like to note that we continuously develop our products. This includes looking at whether this specific noise can be reduced in the current Performance Line CX.&quot;Best RegardsYour Bosch eBike-team</blockquote>

[QUOTE="mlx john, post: 9771, member: 1304"] It's a known issue with these motors. The following is Bosch's offical response, but if you don't want to read the whole thing, in summary they're saying "oh well, tough sh*t". [I]"When riding an eBike/eMTB on rough and technical terrain downhill, vibrations of the chain/chainring often occur. Those vibrations can be transferred to the frame, the drive unit and to the inner gear wheel (inside the drive unit). In some cases when freewheeling, a metallic sound can be generated when the inner gear wheel is not under load. How much vibration and sound is transferred depends on the type of bike (for example hardtail vs full suspension and aluminum vs carbon). The current Performance Line CX is designed with high power density and thermal stability as well as a highly efficient gearing mechanism and incredibly smooth-running gears. Paired with reduced weight, lower wall thickness and improved heat release it is easier for mechanical noises to be omitted. Therefore the noise may sound a little more prominent when compared with other drives. This noise does not have any influence on the performance, functionality or reliability of the motor. Usually an eMTB also makes several other noises as it navigates these technical sections of trail (tyres gripping/skidding, chain slapping etc) and thus any noises from the motor are drowned out. On further request: We would also like to note that we continuously develop our products. This includes looking at whether this specific noise can be reduced in the current Performance Line CX." Best Regards Your Bosch eBike-team[/I] [/QUOTE]

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