Is the AMFLOW this rattley?
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Well like explained from someone before not all motors have the same tolerances from factory, some could be tighter some looser, and not all people run the bikes the same way, heat expands metal so someone pushing really hard in turbo all the time could have closed the tolerance gap with heat metal expansion just enough that it doesn't rattle etc..., someone doing XC trails on eco can't do that, because there isn't enough heat produced from the motor. There are several factors that come into play, there is also the angle of the helical gear teeth, but that's going into technical to much for an online discussion.
After contacting Amflow Support about the rattling and providing them with some videos, I was sent to my bike shop, which then replaced the motor. Unfortunately, the rattling is still present after the replacemant.
Both motors have the DJI cover.
ok, that's useful, so doesn't seem worth getting a replacement if you have the rattle then....., I wonder if any motor with just the Avinox label are somehow different, i would expect not, the rumours around a change in the motor to stop the rattle was from last September, so likely motors now have any change already fitted... and also rattle
We have 3 Amflow in our group. 2 are rattling 1 is nearly silent. All have the DJI logo.
I am in contact with my LBS again. Hope we will find a solution. I also noticed that the rattling noise depends on the gear you're in. Have others noticed this too?
I am in contact with my LBS again. Hope we will find a solution. I also noticed that the rattling noise depends on the gear you're in. Have others noticed this too?
I doubt there was/is any solution for this as this is inherently a side effect of the way the mechanicals work in this kind of motors.
If there were replacements, those were probably initial, as far I have seen(following several treads, fb, yt,...) the recent people that asked about rattling got an answer that nothing is wrong with the motor and no action is needed.
There suposedly was some statement( although I haven't seen an official one to this day) from Dji last year in September that they fixed the rattling with a new motor revision, honestly I think it was just marketing BS. I mean If there was a real statement it would describe why it was rattling in the first place and what the revisioned motor has that it solves it.
Several other brand dji bikes, based on information I gathered from reviewers on fb, yt, and in forums, unfortunately motors do rattle more or less on all of them or develop it later down the line.
I described in my previous post what imo the reason for the differences(some do, some don't) between motors is. My theory is not based just on assumptions, but observations of also my personal experience with 2 Giant Syncdrive Pro2 motors that were pretty silent when new, but over time developed rattle the more they were used and of observations how a serviced motor gears behave when fully greased with proper thick heat tolerant grease.
Don't get me wrong, I am not bashing on the Avinox motor, I think it's a great product, but I am aware on how it's built and that the rattle is inherently built into it, unfortunately for the sensitive folks out there.
If there were replacements, those were probably initial, as far I have seen(following several treads, fb, yt,...) the recent people that asked about rattling got an answer that nothing is wrong with the motor and no action is needed.
There suposedly was some statement( although I haven't seen an official one to this day) from Dji last year in September that they fixed the rattling with a new motor revision, honestly I think it was just marketing BS. I mean If there was a real statement it would describe why it was rattling in the first place and what the revisioned motor has that it solves it.
Several other brand dji bikes, based on information I gathered from reviewers on fb, yt, and in forums, unfortunately motors do rattle more or less on all of them or develop it later down the line.
I described in my previous post what imo the reason for the differences(some do, some don't) between motors is. My theory is not based just on assumptions, but observations of also my personal experience with 2 Giant Syncdrive Pro2 motors that were pretty silent when new, but over time developed rattle the more they were used and of observations how a serviced motor gears behave when fully greased with proper thick heat tolerant grease.
Don't get me wrong, I am not bashing on the Avinox motor, I think it's a great product, but I am aware on how it's built and that the rattle is inherently built into it, unfortunately for the sensitive folks out there.
mine certainly doesn't seem to rattle all the time, not sure if that's the gear related, it def didn't used to rattle so either the grease has thinned or the gears 'bedded' in. Unless there has been some sort mechanical change in the motor i cannot see any motor being rattle free over time
Hope yours stays fairly rattle free then
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I'd love to hear from Rob about the rattley Crestline. Has he tried to get the rattle sorted? What happened. This is crucial information!
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Well, to be honest, I think post 57 tells the story pretty clearly. I think, I want to be game for a Amflow, I really do. But I can't get in this situation:
www.emtbforums.com
Is the AMFLOW this rattley?
I saw that, in this short https://www.youtube.com/shorts/-CEr9byAV7c Mine is like the second. Doesnt rattle by hand. Rattles on the trail on rough sections though. But i am sensitive to sound, much more than those i ride with. I usually hear a loose bolt on their bike before they do themselves.
www.emtbforums.com
Chrysaor
Active member
Do you know more precisely what is the mechanical cause in that particular case and what other design/brand could be more silent? I might be interested by a DJ bike in the future but I could not handle any rattle. I had enough with Shimano in the past
On the contrary my Spe SL 1.2 is deadly silent on the downhill, even in the rougher conditions, not a single noise and it's getting close to 2000km
mrtrinh
Active member
This is probably the most comprehensive theory that I agree with. DJI crestline owner here (also sidekick hub) and I have the rattle. One can argue that the VPP causes the motor rattle but there are some crestline folks who don't have it. If amflow owners have rattle that theory goes out the window. If you watch POV videos of Forbidden E Druid's they also have rattle.
Only thing we've narrowed it down to is if you remove your chain and try and spin your chainring backwards, the more resistance you have the less it rattles. Rob has confirmed this along with other DJI Crestline owners. Avinox logo on the motor doesn't dictate it either (I have the avinox logo on my motor).
In the attached yt video you can see what is gear backlash and how tolerances can have an effect on how it is present or isn't or how heat(metal expansion) and grease can have an affect on it.Do you know more precisely what is the mechanical cause in that particular case and what other design/brand could be more silent? I might be interested by a DJ bike in the future but I could not handle any rattle. I had enough with Shimano in the past
On the contrary my Spe SL 1.2 is deadly silent on the downhill, even in the rougher conditions, not a single noise and it's getting close to 2000km
Straight cut gears tend to have a more distinct gear backlash sound than helical gears where the angle of the teeth under pressure tends to push them apart so there is always some force creating friction that reduces the gear backlash to some extent, but not all.
The Avinox motor has two main straight cut gears, one bigger on the drive shaft that also houses the steeples clutch and a smaller that is then connected to the planetary reduction gearset which uses polymer helical sun gears for noise reduction and better load distribution.
As you can see in the picture here the 2 main metal straight cut geras, IMO these two are most probably the ones creating the rattle due to the factors already described in my previous posts. One factor that I didn't mention also is the steeples clutch mechanism, this type of clutch has nearly instant engagement, which is good in technical terrain climbing where you need that for better over obstacles control.
Although that instant engagement can also bee a downside when going downhill as every single thug and pull on the chainring either by pedals or chain pulling due to suspension working also pulls on the clutch that engages the two main straight cut gears as they are loose when going downhill.
Someone suggested a possible solution to DJI, where the systems sensors could detect when going downhill, the motor would slightly engage the gears to create constant pressure on the gears thus eliminating gear backlash. That would surely increase consumption to some extent, It's a good idea, although I can't say anything more about it without knowing what and how the internals exactly are designed to work.
Bonus for anyone interested, IMO the best video showing the Avinox motor internals and explaining in fairly simple words the way it works.
I took a DJI motor apart that I had. (A pre production one, but I am assuming the final is same design). I was able to recreate the rattle and see exactly what and where it’s occurring:
The way it works is that the Avinox motor spins very fast, and that power has to be geared down before it reaches the cranks. DJI use a planetary gear system to do this. The planet gears sit inside a larger outer ring gear. This outer ring gear and the inner planet have small amount of play so they don’t bind when torque reverses (no forward torque from the motor) eg when you’re pedalling over the speed cut off limit.
When you’re pedalling and the motor is under torque, the planets are pressed hard into one side of the outer ring gear’s teeth, so everything feels solid and quiet.
When you’re coasting or pedalling lightly over the cut-off, the motor isn’t applying torque anymore. At that point, the planets are effectively “floating” in the clearance (backlash) that’s been designed in between the teeth. On rough ground, each bump causes tiny torque reversals (forward / backward / forward), and the planets knock back and forth against the outer ring teeth. That’s the metallic rattle you hear.
Pre Bosch Gen 5 motors and Shimano ep motors also make the noise. It’s a by product of making the motor free spinning and efficient when there’s no assistance (above cut off) and reduces wear and tear.
Bosch solved it on their new Gen 5 by moving to a helical gear reduction with a decoupler clutch. That clutch isolates the chainring from the motor internals when you’re coasting, so the rattle disappears. It required a completely new design versus Gen 4.
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It’s just one of those trade-offs: DJI went for compact power and gearing with a planetary set, and you get rattle as a result.
Some people can’t hear it, or just don’t notice it. Some motors are noisier than others. Noisier ones will probably be easier to pedal over cut off. Quieter ones harder, and theoretically may have more wear due to the tighter gearing inside.
The way it works is that the Avinox motor spins very fast, and that power has to be geared down before it reaches the cranks. DJI use a planetary gear system to do this. The planet gears sit inside a larger outer ring gear. This outer ring gear and the inner planet have small amount of play so they don’t bind when torque reverses (no forward torque from the motor) eg when you’re pedalling over the speed cut off limit.
When you’re pedalling and the motor is under torque, the planets are pressed hard into one side of the outer ring gear’s teeth, so everything feels solid and quiet.
When you’re coasting or pedalling lightly over the cut-off, the motor isn’t applying torque anymore. At that point, the planets are effectively “floating” in the clearance (backlash) that’s been designed in between the teeth. On rough ground, each bump causes tiny torque reversals (forward / backward / forward), and the planets knock back and forth against the outer ring teeth. That’s the metallic rattle you hear.
Pre Bosch Gen 5 motors and Shimano ep motors also make the noise. It’s a by product of making the motor free spinning and efficient when there’s no assistance (above cut off) and reduces wear and tear.
Bosch solved it on their new Gen 5 by moving to a helical gear reduction with a decoupler clutch. That clutch isolates the chainring from the motor internals when you’re coasting, so the rattle disappears. It required a completely new design versus Gen 4.
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It’s just one of those trade-offs: DJI went for compact power and gearing with a planetary set, and you get rattle as a result.
Some people can’t hear it, or just don’t notice it. Some motors are noisier than others. Noisier ones will probably be easier to pedal over cut off. Quieter ones harder, and theoretically may have more wear due to the tighter gearing inside.
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Thanks Rob
John_likes_bikes
Well-known member
Can you post video of what you're seeing/hearing with the motor apart? Would be interresting to see.
I have videos and pictures that I took, but it’s a pre production motor never seen in public and I probably shouldn't post it.
To anwser the second part of your question, you are probably good off with motors that have predominantly helical gears.Do you know more precisely what is the mechanical cause in that particular case and what other design/brand could be more silent? I might be interested by a DJ bike in the future but I could not handle any rattle. I had enough with Shimano in the past
On the contrary my Spe SL 1.2 is deadly silent on the downhill, even in the rougher conditions, not a single noise and it's getting close to 2000km
The new Bosch CX Gen5 is one of those with an additional solution of decoupling the external and internal systems on the crankshaft. Probably the most silent full power motor out there.
The new Specialized 3.1 motor also uses helical gears, although it did have some slight gear backlash when I tried a cut open model at the Riva del Garda festival.
The case of your SL 1.2 motor is interesting, as it does have most straight cut gears that isn't ideal for gear backlash, although the way they mesh is that there is always a metal gear meshing with a polymer gear, or a polymer on polymer, so even if there is gear backlash happening it does not produce the metal on metal sound. The use of polymer gears here is possible due to lower torque figures so less strain on gear teeth.
As the SL is made by Mahle I would place my bet on the new Mahle M40 motor also, looking at the first pics of the internals it looks as a Dji similar design with a planetary reduction gearset although with helical gears and a more polymer gears than the Avinox.
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Great information and thanks for the looksie inside of the motors. I see that there is a decoupler clutch that helps with the noise for the Bosch. Do I assume that it is a "mechanical one way clutch" .
first gen DJI did just that. They have made changes to address this many months ago.
Most rattles have been addressed on the newer generation Amflows
Mine with fox 2026 stuff on it is dead silent, as is my Shimano ep801.
Wrong
The rattling has already been addressed quite a while ago, and its not an Amflow problem it is a DJI problem, and when Amflow had to deal with the customers, they had the problem addressed.
Thats due to people not reading or doing the ground work. A little study here shows DJI addressed the motor rattling quite a while ago. But not everyone rides high miles then reports a new rattle starting that was not there. Most complain that theirs did it from the beginning when the bike was new. Which would be some of the first run motors.
Brilliant, a picture is worth a thousand words.
Nothing supports your theory, people in this thread have only a few months old motors that rattle, apparently they did something to the motor last September, but so many people have bikes later than that date with rattles. Sadly there is not a single thread of evidence to suggest they have changed anything. People on this thread have even had motors replaced for the 'new one' and still get a rattle. Until someone actually opens a motor and confirms a HW design change, it's safe to say some don't rattle due to tolerance, but ultimately all will to some extent due to the design and the makeup of the gears etc
My motor is 4 months old, zero rattle at first then after a load of miles it's got a slight rattle. Easy to reproduce by knocking the crank back and fourth against the motor, like in that video. Based on their motor design they would have had to radically change it (with a decoupler clutch for example) to stop the gear backlash noise. If they had done this there would be at least one thread of evendence supporting the theory. Which there isn't. As I said, mine is 4 months old, was silent and super tight feeling when coasting. Now, as expected it's looser on the coasting but the backlash can be felt/heard
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