Bicycle Mechanics - Deraileur knocking frame

Hi,

I've just bought a Giant Terrago and noticed that if I ran over a bump the rear deraileur knocks up onto the frame. I asked the guy in the bike shop if it needed adjusting but he has simply stuck on a rubber buffer to stop it chipping the paintwork.

I assume that this can't just be a design flaw. Is there any other adjustment that I can do or suggest the shop does. Can they tighten the spring of the deraileur - does this have any drawbacks ?

thanks for any help

Rob

Is it the derailleur hitting the frame or is it just chain slap - the chain hitting the stay? This rubber "bumper" - did the mechanic apply it to the stay?

It is the deraileur knocking the frame, the rubber cushion is cable tied onto the deraileur body - I've hopefully attached a picky

It is the deraileur knocking the frame, the rubber cushion is cable tied onto the deraileur body - I've hopefully attached a picky


looks like a design related issue. i wonder if adjusting the tension screw would help?

ed rader

I believe your chain is too long. Try shifting into the "big-big" combination as see if there is still a lot of derailleur travel left. If so, shortening the chain until it will just allow big-big should solve the problem.

You're not the only one whose rear mech hits the stay on rough terrain. This is the exact reason shimano uses a rubber bumper on their XT rear derailleur. Some of the locals here like to cut out a piece of old tire and zip-tie it to the frame. I have some old road bike bar tape wrapped around the stay and secured with a few layers of electrical tape. I like a quiet bike.

thanks for the replies.

I'll mention some of your solutions when I go back to the shop at the weekend. Meanwhile I think I will also tie a piece of rubber to my stay!
I'll let you know how I get on.

get a decent bike next time :p

The shop said that the chain shouldn't be tensioned too much (extra wear ?) and looking at some of the other (mainly Giant) bikes in the shop seem to have the same issue.

Anyway the shop has been helpfull and fitted some better cross country gears so I'm happy for the moment. Perhaps after this bike has died I'll get a decent one.