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What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 5:22pm
by pulseezar
I bought a second hand bike over the weekend, a titanium Genesis Equilibrium, and it's in tip top condition considering that it's four years old. I have however noticed that on closer inspection that the derailleur hanger seems corroded. The frame surrounding it is fine so not sure how this has happened or if I need to be worried or not. Not even sure it needs replacing as the missing material appears to be just on the outside facing surface.

What do you think?

IMG_20181211_165239.jpg


IMG_20181211_165221.jpg

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 5:26pm
by roubaixtuesday
I think I'd buy a spare to be ready if it does fail - it's useful to have one anyway but if it ain't broke, don't fix it.

It looks really weird on the photo though, as if cyber-mice have been nibbling away...

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 5:29pm
by Brucey
I think you need a new gear hanger; it is meant to be replaceable, so replace it.

Image

BTW if the gear hanger looks like that I'd be really worried that there are all kinds of seized fasteners in the frame, and that other parts (like the carbon to metal joints in the forks) are rotten too.

FWIW the corrosion has become that bad because some moron has fitted a plated steel screw into the mudguard eye; if you are very lucky indeed that will unscrew without shearing off.

cheers

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 5:54pm
by pulseezar
roubaixtuesday wrote:It looks really weird on the photo though, as if cyber-mice have been nibbling away...


It looks weird in real life too! Never seen one like it.

Brucey wrote:FWIW the corrosion has become that bad because some moron has fitted a plated steel screw into the mudguard eye; if you are very lucky indeed that will unscrew without shearing off.


Why is that and what sort of screw should it be?

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 6:02pm
by Brucey
you should really use a stainless steel screw (with lots of copper ease on it) to connect stainless steel (mudguard stays) to a Ti frame. An ordinary steel screw will suffer from being 'the anode' in the corrosion cell which means it will corrode like fury.

This may have helped the gear hanger corrode too, since anything dribbling off the screw would itself be corrosive. The gear hanger is made from some crummy aluminium alloy that will also corrode easily when it is bolted to a Ti frame.

All this corrosion goes at x10 normal pace if the bike is used in the winter and then not washed after every ride; the road salt will eat everything that isn't Ti or stainless steel.

cheers

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 6:07pm
by pulseezar
Thanks for that Brucey. I have ordered a replacement hangar and will have a go at getting those screws out. Thankfully I know the previous owner cleaned the bike regularly so should be okay - not sign of any other problems.

I'll have a look for some new mudguard screws while I'm at it!

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 6:10pm
by keyboardmonkey
a) Find out which derailleur hanger you require
b) Order two

(edit: just seen your cross post of 6:07pm)

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 7:08pm
by pulseezar
I've had a play around with it now. The mudguard screws came out fine and I've replaced these. I think the problem was more likely the washer that had been used. Either way I'll keep an eye on the replacements.

The problem now is that I cannot get the screws on the hanger to shift at all! Hopefully the corrosion will stop or at least slow down now the offending bits have been removed but otherwise it looks like it might need be a trip to the shop to see if they can get it out. Worried about snapping an alley key or stripping the head.

I've attached a couple of photos that show the other side of the hanger. The corrosion seems to have made the metal turn almost fibrous - a bit like the iron filings that you get inside those magnetic drawing toys. Very odd.

IMG_20181211_184326.jpg


IMG_20181211_184415.jpg

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 7:13pm
by Brucey
if the retaining bolts are seized then it might turn into a drilling job. As a holding measure you could sand the area down until the corrosion is gone and then repaint. It probably won't last (and there may be worse corrosion where you can't see it, up against the Titanium) but it may keep you going in the meantime.

[BTW the retaining bolts have pathetically small hexagon sockets in them, which will round out very easily. I would suggest that you fit csk screws with a slotted head as a replacement; you will be able to get improved purchase on those.]

cheers

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 8:36pm
by David9694
Don’t the hanger bolts want a bit of penetrating oil on them?

Re: What would you do if your derailleur hanger looked like this?

Posted: 11 Dec 2018, 8:49pm
by 1066enthalpies1939
keyboardmonkey wrote:a) Find out which derailleur hanger you require
b) Order two

(edit: just seen your cross post of 6:07pm)


This may help you to find the correct hanger
https://www.mountainbikecomponents.co.uk/hangers