Chain Rattle on the Front Cog.. Suggestions needed on what to try...
 

Hi All. Long time forum reader, but just joined up to ask a question after scouring the depths of the internet for some help.

So I've had a rattle on my bike for a month or so... Finally found out what it was after many moments contemplating throwing the bike Into the nearest river... The chain seems to rattle side to side when I hit bumps in the road and rattle on the front cassette cog. Anyone got any ideas... I first thought maybe the chain isnt the right length.... But it's relatively new and put on by my local bike shop a few months back. 2nd thought was the cogs worn down... I have just replaced the wheels as the bearings had gone and the rear cogs were wobbling slightly when ridden.

So I thought I'd post a video too to see if anyone had any thoughts... but I can't do that till I've done 10 posts. So I've done a pic. But I can't post that either. 🤦

The bikes a Cube Attain Pro 2020 model, 9 speed.

So any advice anyone has would be really appreciated. As every road bump causes the rattle and I look so unprofessional cycling past anyone rattling really loudly.

Thanks In advance everyone!
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Post a link with spaces in it. Someone will assist.

Good idea. Thanks. youtu.be /FHCCRQ6xDeM

Here's the link:

It's only 7 s and shows the large chainring with the chain rattling at the bottom.

Chain tension? Chain lubrication?

Hm interesting. Do you have any information on which chain and which chainrings/crankset you have?

It seems like the chain might be too wide for the chainrings. Does the chain have the same amount of play on the rear cassette?

Hm. According to this:
https://www.cube.eu/en/2020/bikes/ro...knorange-2020/

You have a shimano sora crank and a KMC X9 chain. Those should be compatible. I wonder if my bike does this.

Thanks Both. So I've previously cleaned the chain completely and re-lubed and still have the same issue. So I ruled that out.

The chain is a KMC X9 and a sora crank, and that's what the bike came with originally I believe (New chain fitted at it's last service)

I did suspect maybe tension so was my next avenue to go down. But as you said it does seem a bit wide. My other thoughts were maybe the teeth are worn down allowing more movement possibly...

My thoughts also. There's definitely noise when I hit a bump in the road or a small pothole.
Tire pressure affects the feel and perceived noise level, for me.
I'm trying to recall if there's more/less noise if I'm pedalling or just standing on the pedals (getting off the saddle) when hitting a bump/hole in the road.

There's an old adage in bike and auto mechanics that usually helps with diagnosing problems: "Start with the last thing you did to it."

Did the rattle start with the new chain?
How's the derailleur's overall spring tension?
Is the chain too long? Shift into the small chainring and the smallest cog -- it should look like the picture on the left, not the right:

https://cimg3.ibsrv.net/gimg/bikefor...59600fcedd.jpg

Oh yes I totally agree potholes etc would cause it. But I get a rattle even just going over say a not so smooth road. Or over a bumpy bit of tarmac and it's definitely a more recent thing. Never had an issue when I first got the bike last year. It's just so strange. I'll check to see if the chain moves as much on the rear cassette next.

What happens if you put the chain in the small-small combo? Is the chain reasonably tight or is it sagging?
EDIT: Rolla got here while I was typing and explained it better! :)

Do you use both chainrings, or ride mostly on the big one? I'm wondering if one chainring has a lot more wear than the other, so might be useful for testing......

Hi guys, Thanks for all the replies, Really Appreciated, so I went out last night on my bike again, it's happening on the large and small ring at the front so kind of rules them out as an issue as I usually use the larger cog mainly.

But I have had a look at the rear derailleur, and it seems stiff, it's not springing back and forth very freely, seems to stick sometimes. Is this something I could repair do you think if i take it off and clean etc? I'm just a little worried about getting it all set up again correctly. I that's what's causing the chain possibly to sag and in turn rattle on the front ring.

Little disappointing this was never picked up on my last service :( But I'll have a look into it today, YouTube here I come!!

I don't think we've explored the chain length question close enough. You'd think the shop would do it correctly. But there is always a chance they goofed. Easy thing would be to put it in both smalls and see if the chain has tension on the lower run. A pic from the side will help us. If the DR cage is at the limit of it's rearward travel in the smalls, then that's a problem too even if the chain still has a little tension.

As for things seeming stiff.... how do you mean stiff? Does the shifter cable get slack in it when you shift to higher cogs and it takes a while for the slack to come out?

It sounds like you've discovered the cause. Depending on your budget, mechanical knowhow, etc. you should take it to a bike shop, or remove the chain at the masterlink and examine the RD and try to clean, lube, free it up. Replace with a new Sora or other RD if necessary. Make sure the chain is sized to proper length at some point in the process. A bike workstand is a great back-saver for this type of work.

I would hesitate to remove the derailleur; problems are usually easier to diagnose when it's on the bike, and you can clean it just as well on as off. Putting the bike in a stand (or hanging it by the saddle with a rope) allows you to pedal the bike with your hand as you shift the gears. Do that, and watch the rear derailleur to see how it and the chain behave.

I wouldn't start undertaking a derailleur overhaul until you're more certain that's what is causing your chain rattle issue. Again, I'd start with the chain length.

I'd say another video is in order. Show us the springiness of the rear derailleur.

I think your right. So first off I thought id post a pic of the rear derailleur in the smallest cogs to show position. It does look like the chain might be a bit long to me but I'm only guessing.... Chains on the smallest cogs at the back and the front...

I Can't post a pic yet so I've put a link with no http to the pic.
drive.google.com/file/d/1Z9b_m1Zf33C0kepp1tiBFMesXVf8zq9k/view?usp=drivesdk

Here's the pic:

https://cimg3.ibsrv.net/gimg/bikefor...8b39c9a582.jpg

You may be able to remove one link pair. Just because a bike shop does the work does not mean that they set the new chain up at the optimum length. It saves time in assuming that your long cage rear mech can wrap the standard 116 link chain so they just throw it on without cutting.

Great picture! I'd say that the chain is minimally the correct length, but I agree with Moe Zhoost that you could probably take out a link. You just want to be able to put it in the big ring/big cog combo without stretching the derailleur in the other direction.

Just spitballing here, but when I watch the video again, it *seems* like the rattling is coming from somewhere further back from the chainring. It sort of reverberates or flutters after you flick it, and I just don't see how it would do that against the chainring teeth. Is the derailleur's lower pulley wheel secure?


https://cimg9.ibsrv.net/gimg/bikefor...db07d9d7e5.png

Yes, a pair of pics: small-small and big-big would be useful.

Aside from just putting triflow or similar on evry moving/sliding part, is there a set of lube points for derailleurs? (To make sure that the spring can tension the chain easily...)

OP’s picture shows the chain in small / small……chain is too long….take at least a link out…

Likely correct, but hard to know for sure without knowing whether the bike is tilted in the photo (which affects the perceived angle of the rear derailleur cage), so I agree with VicBC_Biker's suggestion to confirm via a pic of the chain on big chain ring in front and big cog in rear.

Hey Guys. Sorry for the long delay. Life got in the way as it does.

So decided today to try taking out a link in the chain.... It made it too short. I was hoping that would be the solution but it appears not to be. Here's a pic with the link back in and the cogs both on the largest rings.
https://cimg8.ibsrv.net/gimg/bikefor...39377b9692.jpg