Bosch gen 4 "bottom bracket"

[fenwick458]

I've had my Wild FS since Feb 21, done 1700km in total. since this summer I have noticed an intermittent rumbling under load , usually towards the end of a ride, which I always thought was the derailleur/cassette but it's been getting worse, and after a good clean and service and confirmation the derailleur is set up perfectly, I still get a rumbling under load....

what's the expected life of the "bottom bracket " bearing in the motor?

Where do I send it to get it fixed?

 

[RustyMTB]

Deleted that as I realise I'd been a knob & not read the question.

 

[Sander23]

I've had my Wild FS since Feb 21, done 1700km in total. since this summer I have noticed an intermittent rumbling under load , usually towards the end of a ride, which I always thought was the derailleur/cassette but it's been getting worse, and after a good clean and service and confirmation the derailleur is set up perfectly, I still get a rumbling under load....

what's the expected life of the "bottom bracket " bearing in the motor?

Where do I send it to get it fixed?

It could also be the front sprocket that's been weared out. I've had it on my bike to. As soon that I changed it the sound was gone

 

[RustyMTB]

Simple test for that is to take off the chain & spin the cranks.

 

[fenwick458]

Simple test for that is to take off the chain & spin the cranks.

I'm sure I tried that but it only does it when under load. I will strip it all down as much as I can and investigate anyway

the first post (that got deleted) mentioned something about replacing bearings, who does that?

 

[RustyMTB]

I'm sure I tried that but it only does it when under load. I will strip it all down as much as I can and investigate anyway

the first post (that got deleted) mentioned something about replacing bearings, who does that?

That was me too. The motor has a bonded seal between the case & the crank & then an outer seal that has grease behind it to act as a barrier to water. Over time, the grease disperses & eventually water can get in. When that happens, it's bad. You can strip them down but you need to take great care, it's very easy to wreck them. Otherwise someone like @Bearing Man will rebuild your motor or supply you with spares for it.

This guy shows you the intricacies of stripping your own motor.

 

[Mteam]

I've had my Wild FS since Feb 21, done 1700km in total. since this summer I have noticed an intermittent rumbling under load , usually towards the end of a ride, which I always thought was the derailleur/cassette but it's been getting worse, and after a good clean and service and confirmation the derailleur is set up perfectly, I still get a rumbling under load....

what's the expected life of the "bottom bracket " bearing in the motor?

Where do I send it to get it fixed?

A worn front chain ring can make a rumbling sound under load, if you are still on the original chain ring then it could be this,or even if the current chain ring is a bit old,it could be this.

The teeth on the ring form into sort of hook shape and don't release the chain correctly as each chain link leaves the ring, this makes a sound very much like a rumbling noise.it only makes the noise under heavyish pedalling.

 

[fenwick458]

That sounds like it could be the culprit! any recommendations of what front ring to get?

 

[Stihldog]

Might be a good time to upgrade the drivetrain. (Chainring, chain, cassette).

If you’ve developed some chain-suck your consumables are starting to fail. 1700km+ seems about the time to start charging these worn out parts. Servicing, grit and use plays a factor in the life of these components. Like it was said here, isolate the motor by removing the chain and check for noise, movement, bearing slack etc.
I keep a spare chain and chainring and cassette. They don’t all wear out at the same time.

 

[fenwick458]

I was surprised to notice the ring actually does appear to be worn, 1700km is not that much, I put 3500 and 2000km on my last 2 bikes(non E) and never even considered replacing the chainring as they both seemed fine so it must be an e-bike specific thing, the accelerated wear.
whilst looking for chainrings I noticed the steel versions are half the price
E*Thirteen E*Spec Chainring 34t Steel Bosch CR4USA-100
that seems like a good idea?
the chain is only 500km old and the cassette seems fine I can't see any wear and the gears never skip

 

[E-MAD MALC]

E-Thirteen E Spec Steel Direct Mount Chainring | Tredz Bikes

E-Thirteen E Spec Steel Direct Mount Chainring £30.00 or available with 0% APR finance on baskets over £99. All E-Bike Chainrings are delivered free to the UK mainland*, 365 day returns & Price Match. Buy Now.

www.tredz.co.uk

This is the chainring i use with my sram GX chain, cassette and rear mec

 

[Jhagst]

Make sure you get the special tool to tighten the front sprocket lock nut. They are known to come loose on Bosch motors. Also keep and eye on your cranks if they are E-13
The motors themselves can last thousands of miles.

 

[jonmat]

That sounds like it could be the culprit! any recommendations of what front ring to get?

I have a 2021 Wild FS and did a transmission overhaul yesterday. Mine was bought in January 2021 and the steel chain ring is still in good condition. I have a spare replacement Burgtec, but can't see the point in fitting it. My bikes done 3,200 miles, that's 5,149 km. The older Gen 3 Bosch motor used to eat chain rings in a short time, the Gen 4 Bosch CX has double the amount of teeth and seems to be much more resilient. https://burgtec.co.uk/product/104mm-bcd-inside-fit-e-bike-steel-thick-thin-chainring/

 

[Bof4dznuts]

hi lads new here and this thread seemsnto be as close to my symptoms as possible I find in my 2 highest gears ( that would be used mostly on my work commute) my chain is hopping like fook, I'm also getting my chain ring rubbing off my chain guard so much so that it has cut into it, have any of you ever experienced the whole motor moving on the mounts? it seems that no matter what I do down the back end ie cassette derailleur etc but the chain isn't lining up when it's leaving the chain ring so it's like it's catching the chain as one of you said when the chain ring is worn. I'm stumped lads so any feedback is greatly appreciated oh and on inspection of the back end of her I found the chain had actually snapped a link

 

[Stihldog]

hi lads new here and this thread seemsnto be as close to my symptoms as possible I find in my 2 highest gears ( that would be used mostly on my work commute) my chain is hopping like fook, I'm also getting my chain ring rubbing off my chain guard so much so that it has cut into it, have any of you ever experienced the whole motor moving on the mounts? it seems that no matter what I do down the back end ie cassette derailleur etc but the chain isn't lining up when it's leaving the chain ring so it's like it's catching the chain as one of you said when the chain ring is worn. I'm stumped lads so any feedback is greatly appreciated oh and on inspection of the back end of her I found the chain had actually snapped a link

View attachment 118616

If you have the tools you could check a number of things that could be the culprit.

-Motor mount bolts (#40 torques plus @ 20nm)
-Motor bracket bolts.
-Chainring wear.(chain-suck)
-Castle nut torque.
-Derailer cage.
-Derailer hanger.
-Excessive chain wear.
-Barrel adjustment (derailer)

But a broken chain link. Replace the chain or install a quick link. (I would only install a second quick-link as a temporary measure.

These motors can exert a lot of torque and if your cadence is too low …things are gonna break or wear out prematurely.

A decent LBS may be able to help solve the mystery.

 

[Bof4dznuts]

A worn front chain ring can make a rumbling sound under load, if you are still on the original chain ring then it could be this,or even if the current chain ring is a bit old,it could be this.

The teeth on the ring form into sort of hook shape and don't release the chain correctly as each chain link leaves the ring, this makes a sound very much like a rumbling noise.it only makes the noise under heavyish pedalling.

this is what's happening with me it's a melt I just had my bike in pieces trying to figure out wtf is going on the jumping in furdt gear is doing my beak in

 

[Bof4dznuts]

If you have the tools you could check a number of things that could be the culprit.

-Motor mount bolts (#40 torques plus @ 20nm)
-Motor bracket bolts.
-Chainring wear.(chain-suck)
-Castle nut torque.
-Derailer cage.
-Derailer hanger.
-Excessive chain wear.
-Barrel adjustment (derailer)

But a broken chain link. Replace the chain or install a quick link. (I would only install a second quick-link as a temporary measure.

These motors can exert a lot of torque and if your cadence is too low …things are gonna break or wear out prematurely.

A decent LBS may be able to help solve the mystery.

Thanks for the reply good sir I've went over everything for the last few hours, therapy as it may be to us it's a bitter sweet outcome, I've managed to eliminate my loose mounts theory so that's good, I've come down to it needing a new cassette and chain maybe a chain ring also, also thank you for your reply mate

 

[Ark]

Someone asked the other month on the Bosch EMTB facebook group how long peoples motors had lasted and there were loads of people posting photos of 10,000-30,000KM

some were saying their bearings got a bit sloppy around 6000miles and they replaced them with no problems since.
all the failures we see of people around 500-1500km are probably the unlucky ones.

 

[Bof4dznuts]

Someone asked the other month on the Bosch EMTB facebook group how long peoples motors had lasted and there were loads of people posting photos of 10,000-30,000KM

some were saying their bearings got a bit sloppy around 6000miles and they replaced them with no problems since.
all the failures we see of people around 500-1500km are probably the unlucky ones.

I'm glad I ain't one of them so thanks to the advice here I've been able to narrow it down to chain, cassette and chain ring all of which I'm replacing. I'm sick it's not running right because we got a cracking day for it down here in wexford, not too sunny not raining and me with a sick bike