Bosch Performance CX creaking sound

[Sijmes]

Are you sure it's not your crank arms that are creaking ? It's a similar sound caused by the same pedaling motion.

 

[Bearing Man]

What we have found is that creaking from almost anywhere else on the bike will travel down the frame and emanate out from the motor area. This so far has included:
Seat post
Crank arms (as @Sijmes mentioned)
chain ring to spider securing bolts
rear suspension linkage, including shock mounts, rear quadrant mounts.
Rear wheel spindle
Handlebar stem (believe it or not!)
Pedals

It is sometimes worth trying your bike stood up, as this puts your input torque through different parts of the bike and takes it away from others. Or sit down and pedal one handed etc.
If someone (maybe the bike manufacturer) has greased in between the frame and the motor you will never get it to stop creaking. In this case we drop the motor and clean all contact surfaces with brake cleaner to ensure they are totally clean, this will then cause the aluminium bracket to "bite" against the aluminium frame and it stops it moving.

 

[Richardsuperstar]

I've pretty much checked everything else. I've moved my weight around whilst not pedalling and all is silent. I did think pivot points but doesn't seem to be. It's only when I pedal it makes a noise especially when past the assistance speed or with motor off. I've cleaned and torqued most things now and changed pedals and cleaned seat post. It could be play on the chain ring I guess so that's my next avenue.

 

[Sijmes]

If your chain ring come loose then it gets really loose within minutes, but mine still made no noise, just switched gears badly because the chain line kept changing. I traced the creaking to my engine mountings by standing next to the bike and leaning it away from me by about 45 degrees and standing on the pedal in the 6 o'clock position. This wouldn't always creak, but definitely would do, when I did the same on the opposite side and vice versa.
I earlier had and issue with my cranks coming loose and had removed, cleaned and retorqued a few times. The trick was either with or without grease and I can't remember which 🫤.
I have been convinced up until now that the Bosch motor in an alu frame was the best and most robust option, which surprises me that you're ready to throw in the towel. I'm not convinced that there is anything better. Try the sideways pressure and let us know, good luck

 

[JP-NZ]

What year is the Rail 9?
Do you have creaking under power from both sides?

Here's my post from the Rail 750wh thread.. If you haven't already remove and re-seat the bearings (#3) as shown in the 2022 Parts manual page 4 (I believe the setup is the same for alloy frames). Also make sure to have plenty of grease around the moving parts. Parts manual is last post on this thread below.

Rail (625Wh) - Trek Rail Parts Diagram - Carbon

MY20 Rail Carbon Parts Quick Reference

www.emtbforums.com

Well… the creak came back worse than ever. So back to the dealer for the 2nd time and got to deal direct with the mechanic this time.

He said commonest creak on the rail is rear axle and bearings. Now someone posted that exact area on another thread so well done to them. Mechanic removed the rear inner and outer bearings on both sides, re seated them squarely and greased them.

PERFECT! Creak is gone and dead quiet whilst pedalling. Very very happy in a simple fix that I don’t have to pay for.

 

[Bearing Man]

I've pretty much checked everything else. I've moved my weight around whilst not pedalling and all is silent. I did think pivot points but doesn't seem to be. It's only when I pedal it makes a noise especially when past the assistance speed or with motor off. I've cleaned and torqued most things now and changed pedals and cleaned seat post. It could be play on the chain ring I guess so that's my next avenue.

OK, I am going to say that this is definitely not coming from your motors frame brackets. If it starts making a noise when you take 380% of the power away, something else is going on!
If you do check the chainring to spider bolts, they won't usually be loose, they just won't be tight enough and this allows movement between the chainring and spider and although all feels tight it can make some very annoying noises.
The odd thing is that with the motor on and set in a low power mode, the motor is probably putting in as much effort as you are when the motor is off, but you are getting no noise. The only difference here is that you are not physically twisting and bouncing the bike by putting a large effort in to keep going, this again points to suspension pivot, rear wheel axle moving in the frame or even a cracked frame!
One other thing you might find helpful. If you ride with your head looking forwards your ears cannot sense if the noise is coming from the front, rear or centre of the bike, everything sounds like it's coming from the centre. If you find a clear piece of land and ride while looking to the left or right, you will hear more accurately whereabouts the noise is located.

 

[Richardsuperstar]

I thought I'd give an update on this a month later and for some reason the noise has magically fixed itself. It may be that my thorough cleaning of the plates and frame where they make contact when I put the motor back was so amazing it allowed the aluminium to bind or it's just simply a miracle. Months of noise and then gone.

 

[andygua]

reading never was my strong point! anyway, sod the copyright.
View attachment 106185

Hey @Bearing Man, thanks a lot for this information! Finally found it here. Just to confirm, are the part numbers on the bottom right (the mounting plates) for the BDU4XX unit? I found that my drive-side bottom plate is stripped (on my 2022 Trek Rail), and have been looking for the right part number to replace it.

Thanks in advance!

 

[Bearing Man]

Hey @Bearing Man, thanks a lot for this information! Finally found it here. Just to confirm, are the part numbers on the bottom right (the mounting plates) for the BDU4XX unit? I found that my drive-side bottom plate is stripped (on my 2022 Trek Rail), and have been looking for the right part number to replace it.

Thanks in advance!

Bosch only offer the brackets for the new BDU3 "Smart System" Gen 4 motor. Although, I'm not yet sure what the difference is, if any! If you're in the UK, just drop me an email. We have loads if you need one.

 

[RiderOnTheStorm]

@Bearing Man that's great info! I also saw that bosch sells these mounting plates for CX Smart system (BES3).

They have a long version (EB1120000T) and a short version (EB1120000U).

Which one would be suitable for the CX motor non-smart (BDU4xx)? Thanks!

 

[Bearing Man]

@Bearing Man that's great info! I also saw that bosch sells these mounting plates for CX Smart system (BES3). They have a long and a short version. Which one would be suitable for the CX motor nonsmart (BDU4xx)? Thanks!

There are 4 brackets, one short left, one short right, one long left and one long left. But as I said, there is no part number for the Gen 4, only the Gen 4 "Smart" I do not know if these parts are the same so I can't tell you whether they are suitable? I will try to find out for you.

 

[RiderOnTheStorm]

Thanks a lot! That would be super helpful I've been trying to find these mounting plates for my BDU4xx motor for some time!

 

[Bearing Man]

Thanks a lot! That would be super helpful I've been trying to find these mounting plates for my BDU4xx motor for some time!

As I said, we have tons of them! Our partners probably have these brackets too!

 

[Bearing Man]

Normal Bosch Gen 4 mounting brackets have smaller holes for the screws that secure the bracket to the motor. Other than that the brackets are identical. Fitting the "smart" brackets to the earlier Gen 4 would make mounting the motor a bit more difficult. And would also be difficult to stop the brackets moving after the bracket screws had been tightened.

 

[RiderOnTheStorm]

Thanks @Bearing Man for taking the time to check fhe feasibility on this.

 

[Richardsuperstar]

I thought I'd give another update on the creaking noise. After a return of the noise I thought I'd have another investigation after reading a post where someone said that losening one bolt at the rear stopped the noise.

What I found was when refitting the motor, doing up the bolts on the drive side firmly would leave the motor sitting snugly on 5 bolts but leaving a 1mm gap on the lower non drive side.

Now first I thought when tightening the bolt the frame would easily bend in to fill the gap but looking at the position of the bolt holes (right on the corners of the frame) and the thickeness of the metal I can't see this happening so next option is the mounting plate on the motor would be bent outwards towards the frame. But again seeing the thickness of the plate and distance from the tiny screws attaching it to the motor case this isn't going to happen easily.

So what I think was happening is that the plate was being bent out putting horrendous strain on the tiny screws holding the plate to the motor causing a creak.

So what I did was find a washer that fit snuggly in the gap and tightened up and all has been well ever since.

Looking around for these mounting plates I've seen some have gaskets so I'm wondering if the gap is to accommodate these and sometimes the bike shops don't fit them

 

[Bearing Man]

I thought I'd give another update on the creaking noise. After a return of the noise I thought I'd have another investigation after reading a post where someone said that losening one bolt at the rear stopped the noise.

What I found was when refitting the motor, doing up the bolts on the drive side firmly would leave the motor sitting snugly on 5 bolts but leaving a 1mm gap on the lower non drive side.

Now first I thought when tightening the bolt the frame would easily bend in to fill the gap but looking at the position of the bolt holes (right on the corners of the frame) and the thickeness of the metal I can't see this happening so next option is the mounting plate on the motor would be bent outwards towards the frame. But again seeing the thickness of the plate and distance from the tiny screws attaching it to the motor case this isn't going to happen easily.

So what I think was happening is that the plate was being bent out putting horrendous strain on the tiny bolts holding the screws to the motor causing a creak.

So what I did was find a washer that fit snuggly in the gap and tightened up and all has been well ever since.

Looking around for these mounting plates I've seen some have gaskets so I'm wondering if the gap is to accommodate these and sometimes the bike shops don't fit them

Well done for persevering! It's very unusual to have any gaps between the motor and frame, but your solution seems to have done the trick! As for gasket, there is a "damping film" (gasket) fitted to some early Bosch motors (Gen 2) but this was next to useless! Once fitted, it compressed and as the motor moved slightly it would wear away causing the motor to come even looser and to start creaking badly.
I just want to state again, when we talk about the motor bolts or motor being loose, this usually means that they are tight, but just not quite tight enough.

 

[Beekeeper]

After years of no creaking after tightening up the motor bolts (gen 2 Bosch) the dreaded creak returned the other day. The two large bolts shown here were loose. Tightened these two back up to 24nm (the limit of my torque wrench). I’m guessing over time the aluminium compresses and these need tightening up eventually.