Ali89

Recently my drive train has been making a really loud rattling noise. It sounds to me like its coming from the jockey wheels but I don't know why it is. Here's a video of it, sorry its a little short. Noise occurs both in the large chain ring and the middle (but quieter) on a triple chainset. Is it easy to bend a hanger? The bike hasn't taken any impact on that side. https://youtu.be/9jLkJYs4EmI thanks

Andrew R Stewart 

The first thing I would look at is a bent hanger and a twisted cage because I can tell by eye these aspects (and don't need a tool or measuring device). The "Index adjustment" is also seen during these visual checks. Then I'd look at the wear rate on the chain, cogs, rings and pulleys (some which do want a tool or measuring device).

How old is the system? how many miles on each part? Andy.

corrado33

Clean/lube the chain, clean/lube the jockey wheels. It's quieter in the smaller chainrings because the derailleur is stretched out less. (less pressure on the jockey wheels.)

Ali89

Hi, thanks for the replies.

The drivetrain is all very new, the chain has around 200 miles and wash freshly degreased and lubed etc. The cassette is older but only a month or two, i'm not sure on mileage. The derailleur is pretty new too.

I thought maybe the hanger too, not sure how it happened though.

dsbrantjr

If you used a water-based cleaner on the chain, how did you dry it? Water is very difficult to get out of the crevices of the chain, and if not gotten out will interfere with lubrication and form a water-oil emulsion which is a poor lubricant.

The hanger could have gotten bent, unbeknownst to you, by being bumped while the bike was parked or something similar.

Ali89

Yes I guess so.

I use compressed air to blow most of the air out and then leave it for a while.

dsbrantjr

That may well be the problem, that there was water left. I put my chain in a pan in a 250 degree oven for half an hour to vaporize the water; blowing and air drying probably won't cut it. Think about water between two panes of glass; once in there it will stay for weeks.

I'd try cleaning it again, doing the oven treatment and re-lube. Check the derailleur/hanger alignment as well.

Andrew R Stewart 

And understand that as parts wear they can/will not mesh as smoothly as they did when new, independent of the clean/lube aspects. Andy.