bosch gen 4 rattle, reply from bosch

[KeithR]

I either don't have this rattle on the gen 4 motor ..or my ears really are too fkd to notice ?

No, it could be both..!

 

[Jamze]

I have a theory but I need some feedback before I strip another Gen 4 motor. Can someone try going over a peace of ground that would normally cause the rattle but without their feet on the pedals? Obviously, do not pick a piece of extreme terrain that would end in certain death without feet on pedals. Also mind your plums! ? But feedback would be helpful for workshop testing ??

@Bearing Man Tried it today. Makes no difference on mine, you get the rattle with your feet off the pedals too. Alu framed bike.

 

[Mikerb]

It does seem that some bikes using the Gen 4 motor have the rattling noise whilst others do not..or at least it is far less noticeable. I believe the difference, apart from the acoustic effect of the frame material, must be in either rear suspension design, rear shock set up, or derailleur design......ie put together, the way in which the chainstays/drive train agitate the chain and therefore the chain ring.

 

[Bearing Man]

It does seem that some bikes using the Gen 4 motor have the rattling noise whilst others do not..or at least it is far less noticeable. I believe the difference, apart from the acoustic effect of the frame material, must be in either rear suspension design, rear shock set up, or derailleur design......ie put together, the way in which the chainstays/drive train agitate the chain and therefore the chain ring.

I agree, it would appear to be something to do with "chain slap" agitating the crank. Just need to get @Jamze to ride down the same hill without a chain on
I began to dismantle a Gen 4 last night and hopefully get time for further investigation tonight.

 

[Jamze]

I have a Whyte like Jamze, but I can't say I detect anything I would deem an untoward rattle.

If it is something to do with chain slap agitating the crank, could it be influenced by different drivetrains and derailleur clutches?

Possibly. Mine is GX 12 speed. Yours is 11? The noise reminds me a bit of my bike with 3x gears. When you coast downhill on rough ground on that the chain rattles against the front mech cage. But on the Whyte, it's more of a knock from inside the frame/motor area.

Some folks say it's cable slap or battery rattle - but it stops the second you start turning the cranks again. I ride XC/Trail, so doesn't bother me. But I could imagine if you rode DH on a Bosch bike it would get annoying.

 

[Hamina]

Remove the chain and derailleur and make a test in downhill.

 

[Rob Rides EMTB]

This is what I believe is causing it

Backlash (engineering) - Wikipedia

en.m.wikipedia.org

 

[Jamze]

I agree
My point is that maybe different drive trains, chain engagement, chain tension etc, exacerbates that backlash more than others.
Explaining when some people have it and others don't.

A good analogy...

'It can be heard from the railway couplings when a train reverses direction.'

 

[Hamina]

Has anyone seen pictures of parts inside CX4 motor? Does it make sound if you shake it?

If it would be the drivetrain (chain etc.) then the problem would be much much wider including analog bikes.

Btw. I started to head the sound again now that I have read this thread.

 

[ggx]

After my bike had a service and I complained about it, this noises had decreased a lot, so I supose lot´s of this noises are cable and tightening bolts related, and not about the motor it self.

 

[Vinnykiwi]

This is what I believe is causing it

Backlash (engineering) - Wikipedia

en.m.wikipedia.org

The e8000 did not rattle (much) the EP8 does, surely Shimano would not change the gog specs to create more backlash? I believe the disengagement over and beyond the motor assistance and the resulted reduction of drag (EP8 & Gen4) has more to do with the rattle?

 

[Sean1.0]

This is what I believe is causing it

Backlash (engineering) - Wikipedia

en.m.wikipedia.org

The slip diff on my '69 Alfa does the same... good to know engineering tech has advanced so much

 

[Jamze]

Note...'but in actual practice some backlash must be allowed to prevent jamming'.

After my bike had a service and I complained about it, this noises had decreased a lot, so I supose lot´s of this noises are cable and tightening bolts related, and not about the motor it self.

You'll prob find there's now lots of grease in there? But yeah something being loose would amplify it - must check my bolts ?

 

[Mikerb]

Straight cut gears invariably rattle ( and whine!!). Helical gears resolve both issues but are not as strong which is why transfer gears and gearboxes in motor sport are invariably straight cut. So "back lash" is not doubt what causes the noise. The smaller overall casing of the Gen 4 and EP8 motors means much less noise insulation.
The question is not whether backlash causes the noise but rather what causes the backlash. That can only be forces transmitted through the chain to the chainwheel and crank.
My wife's Gen 4 Cube hardtail does not rattle. My Whyte E180 RS gen 4 does not rattle. I believe different derailleurs make for a marginal difference. I believe the biggest factor is the design of the rear triangle and how it is controlled by the shock. That rear triangle can be more or less linear in action and the shock can be more or less linear/progressive at the beginning of the stroke with more or less LSC and LRS user configured adjustments.
A more progressive rear triangle coupled with a rear shock set up fairly stiff at the beginning of its stroke would I reckon be the worst case scenarion for chain agitation and therefore motor rattle.
Or I could be Wrong!!

 

[Alain78]

This noise I also have on my engine and it comes from the engine, when you take the plate in one hand and want to turn it back and forth I reproduce the noise, so it's good in the engine . At first it bothered me, but you get used to it.

 

[sunstoner]

Im certainly in the camp of not minding the rattle. Its definitely there but I really dont mind it. In fact ive got so used to it I find it to be a reassuring noise as odd as that sounds.

 

[Jamze]

This noise I also have on my engine and it comes from the engine, when you take the plate in one hand and want to turn it back and forth I reproduce the noise, so it's good in the engine . At first it bothered me, but you get used to it.

Agreed. I hear the same clunk when I first spin the chainring backwards when cleaning the chain.

 

[Hamina]

It's really interesting to know what technically happens inside the motor when you hear the sound. Maybe the Bosch Performance line CX Gen 4 has just been too reliable that "no one" has had a reason to disassemble the motor. If it would be Brose case, then we would aldready have hundreds of pictures ?

 

[Rosemount]

I have a Cube stereo 160 with Bosch gen 4 .
Yes it rattles when descending over rocks and roots . I noticed how much quieter the Brose motor in my Levo is compared to .

 

[Vinnykiwi]

Sorry @Bearing Man can’t ride as we have too much snow in Austria ?? at the moment.?‍

 

[dpr517]

Hey there. New to this forum which I found when I searched for reasons why my new Trek Rail 9.8 was making so much noise on the downhill. I thought it was the battery compartment, but tried going down some stairs with the battery removed and the noise is still there. It only happens while coasting. The bike is silent when pedaling through bumps. Sounds like the classic Bosch motor rattle.

Anyone have an update or a fix or response from Bosch where they take some responsibility?

I haven't yet complained to the guys at my bike shop about it. If needed, I'll just get used to it and ignore it, but I would never tolerate this much chatter on my regular mountain bike.

Trek Rail is otherwise awesome and I am having a blast on my first emtb.

 

[Beekeeper]

My understanding is that when the motor was being designed there was a choice to be made of having a rattle but with a motor that was powerful, light and very reliable with great performance.

The other option was no rattle but a compromise on performance / reliability etc.

 

[Cb750stu]

I know my motor rattles but I can't hear it with a full face helmet on and Anthrax blaring in my lugs ?

 

[Mikerb]

I understood from Bosch that they made a design choice to have a looser meshing of 2 gears in order to reduce resistance........the downside being the 2 gears when not being driven are free to rattle against each other. It seems that the rattle is worse on some bikes than others and I believe that is due to differing rear suspension designs having more or less kick on the chain when coasting.
The main drive wheel on the crank meshes with a pinion wheel and both are straight cut rather than helical, that is possibly the source of the rattling. Straight cut gear meshing is stronger but noisier than helical mesh and more prone to rattle.

 

[highpeakrider]

I’ve never had the issue on my Whyte, not sure if it’s the motor angle but I’m very pleased with it.

 

[Mikerb]

Same....mine is the E180RS and I do not get the rattle noise others describe. My wife has a Cube Access (hardtail) with the same motor and that one does not rattle either.

 

[Mteam]

I don't notice any rattle on my Orbea wild fs. On my second motor now and they both don't rattle, or if they do I don't notice it.

 

[Jamze]

and I believe that is due to differing rear suspension designs having more or less kick on the chain when coasting.

Sounds feasible, but we have some Whytes that rattle, some that don't, and some that didn't but now do!

 

[Mikerb]

rear shock needs servicing then!!

 

[Paul Mac]

I think they only rattle if your smashing it!
Mine rattles lots ?