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 ?
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
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.
Scott CR1 SL, Giant TCR-C0, Fisher Sugar, old Cannondale, Lemond Tourmalet
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.