aidan.duffy

Hi,

I am fairly new to biking and have an issue. I recently bought a bike to ride around the city (Trek FX 1 Disc). It has been great so far but now I am having an issue.

While pedaling forward, sometimes the rear derailleur will fold or bend which causes my chain to become very loose and will make a loud vibrating noise. All I have to do is begin pedaling backwards and immediately it will re adjust and everything is fine. This happens very frequently now when I ride my bike and I am unsure how to fix it.

Any help would be greatly appreciated.

Thanks

Broctoon

I recommend taking it to a bike shop to have them the check the derailleur. It might just need a simple adjustment.

aidan.duffy

Yes I may do that. I was hoping to be able to make the adjustments at home tbh

Broctoon

Perhaps you can. For some guidance, you might post in the Bicycle Mechanics subforum. If possible, post a video there of the malfunction occurring. This will give people the best chance of understanding what's really happening.

aidan.duffy

amazing thank you. I will do so now.

VegasTriker

As a newbie you will not be able to post pictures until you reach 10 posts. You have four so far. From your description it seems as though the chain is catching on something in the lower part of the derailleur (idler) and pulling it forward . See a diagram here for the parts of the derailleur so you can use the correct terminology. https://fresnocycling.com/Shop-Talk/6339982 It is possible that the RD is worn or damaged or the chain has been damaged. The first thing is to carefully check the chain by flipping the bike upside down and rotating the cranks while you watch the chain for damage as it goes around the idler. If your chain has a master link, you can buy a chain, shorten it to the right length and install it yourself. If the rear derailleur is damaged and you haven't done any bicycle repair, you might want a bike shop to fix that. There are lots of YouTube videos on how to replace a rear derailleur.

zactaylor

Can also happen when the jockey wheels are not running straight. The teeth could be too worn or the whole cog could be loose.

Iride01 

If it's a new bike you should take it back to the shop. Trying to learn what to fix on a bike that isn't working well can have you confused about what really does what. It's better if you know what does what before you try to make something do what.

Most bike shops stand behind what they sell for a year maybe two. And if it's actually a warranty issue, then Trek needs to know that something is happening.

You don't list your country. A lot of the shops here will let persons watch while they work on the bike. So you can learn a lot by watching and asking questions about why their doing that to your bike.

wheelreason

If this is a fairly new bike, just take it to the shop you bought it from, and have them adjust it. This is one of those things that will be very easy for some one with experience to diagnose and repair, but tricky for most novice cyclist/DIYer, there are several things that may be causing it. Also, while unlikely, it is possible for the dlr to get hung up and bend or in extreme cases get ripped out and possibly damage the frame or wheel, and even cause an accident.