Another broken rear derailleur

bogmanfan

Coming home this afternoon. Stopped at lights on North Circular Rd. Pulled away when they went green and all hell broke loose. Chain came off and jammed in between the spokes and the cassette. Derailleur bent inwards and broke 2 spokes on my rear wheel, which also seems to be buckled now :eek: Had to wheel the bike to the edge of the road and, after inspecting things and call for a taxi.

This is the second rear derailleur that I've broken in just 4 months (both Shimano 105). Drivetrain is kept clean and regularly oiled. In fact, I had oiled it on Saturday. What's up? Am I just putting out so much power that the derailleur can't handle it? Would an Ultegra derailleur be any stronger?

victorcarrera

You have got to find out what is causing the chain to over shoot the largest sprocket. It is more than likely the low stop adjustment screw and when the chain falls in there and jams it pulls the rear mech arm in after it.
A pie plate would prevent this.

abcdggs

Are you doing your own maintanence?? If you are STOP! go to your LBS. Otherwise, change shop.

Holyboy

Sounds like your gear hanger is getting bent some how, if it was a matter of bad limit screw adjustment then the mech would overshoot in the first few times you shifted to the largest rear sprocket and not wait awhile to do so.

Do you put the bike in a bike rack to lock it at work or any where else?

Do you transport the bike in a car at all?

Does your bike fall over much?

Does your OH kick your bike when you're not around?

All these things can cause hangers to bend!

bogmanfan

Holyboy wrote: »

Do you put the bike in a bike rack to lock it at work or any where else?

Yes, every day at work. And I had only left work a few minutes when it started acting up. Our bike racks are pretty packed, so it could have gotten a bash from someone else's I suppose. Will have to be more careful about where exactly I lock it up in future.

Roadtoad

Bad luck there.
When I got my Giant with Shimano 105 bits the factory/LBS set up the back wheel incorrectly and a spacer had to be added or moved from one side of the axle to the other. When this was done the overtravel allowing the chain into the spokes stopped, but only after it cost me lots of spokes and ultimatly a new wheel.

I've just changed my derailleur after 10,000 km of use, so no complaint there.

Mycroft H

Am I the only one that likes the pie plate? I try keep the rear mech well adjusted but there is always that chance someone has hit it about in a bike rack and knocked it out of adjustment.

lennymc

BX 19 wrote: »

Am I the only one that likes the pie plate?.

yes

pie plates should only be seen when they have pie on them: