Are all derailleurs bent...

[graffian]

Just got another bike and it's got a bent derailleur!
My first bike had a bent derailleur, but that was from sliding sideways down a muddy bank, maybe the smooth tyres weren't such a good idea, or maybe I should keep off the bridlepaths;-)

Anyway I now need to fix bike number 1 to flog it, I suppose I better fix bike number 2 while I am in the mood[have the stilsons in my mitts]. Do you just take a Stilsons and give the bit with the idlers a little/gentle tweak?

 

[duncmc]

Generally I would say yes, but it does depend which bit is bent and how much. How do you know it is bent? Are you standing behind the machine to look at it? Is the the mech hanger that is bent, the body itself, or the plates with the jockey wheels in?
Also what type of mech is it, make, model and what is it made out of? My mate who has 30+ years of being a bike mechanic is always tweaking them with a big pair of stilsons.

 

[Sean]

Yep - set .of big adjustables and some "cold setting"

The jockey wheels should be parallel to the rear sprockets.

They are quite soft so they don't break when you drop the bike.

 

[chunkolini]

Check that the mounting is not bent first, take the derailleur off , then with a mole grip clamp a pice of flat strip to the mount and see if it is straight, it gives you a longer line to sight along. if it is aluminium it may well snap off as you tweak it. if the deraileur is bent give it a tweak, firm but gentle is the way.

 

[stuvy]

I used to have a derailier hanger bar on one of my bikes. Like this,
http://www.edinburghbicycle.com/products/derailleur-guard

 

[hotrodder]

Mech hangers/dropouts are often ****** even on new bikes, derailleurs usually* only end up bent after dropping it/clouting something which'll can move the the hanger too, especially the replacable type (some of which are made from chocolate and move if you look at them too hard).

This is what the proper alignment tool looks like... http://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment The Shimano one is better, both are probably horrifically expensive for what they are hence many eyeballing things with stilsons or the like. The rear mech mount is M10x1.0, easy to knock up something that'll align things to the wheel.

FWIW dropout alignment tool, again easy to make something with some big washers and a bit of bar/studding... http://www.parktool.com/blog/repair-help/dropout-alignment


* the one big exception being if the bike was assembled by a monkey who just grabbed the mech and twisted everything to get the alignment close enough for the gears to work

 

[graffian]

* the one big exception being if the bike was assembled by a monkey who just grabbed the mech and twisted everything to get the alignment close enough for the gears to work

You have been watching me...

I bolted the bent derail thingie to a block of metal, yes it was bent and straightend the bit the wheels are in, it was dead easy. I knocked up a thing to check the frame, looks just like hotrodders link, if you squint a bit/don't put your glasses on[if your a speccy git]; the hanger bit is out. My derailleur looked just like the top picture on the link, I guess, I only ever looked down at it, but it changed gear fine and I rode it for a year like that, I bent it a bit more and obviously effected the movement as it changed up so the chain got caught between the sprocket and frame! Claude, the £10 bike, has Shimano something_or_otherX bit's. The newer bike has shimano deore XT bit's, which looks nicer than the old bikes stuff.

I was hoping to get my £10 back on the old bike, to go towards the outrageous sum of £40 I paid for the newer one. I just stood back and looked at the bike and though £10 er maybe not;-) Still got to get a tyre and the saddle looks pretty ****ed.