Oh bugger

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Jacomus-rides-Gen

Jacomus-rides-Gen

New Member
Location
Guildford / London
I have just knocked Gen off the repair stand :sad::sad::sad::sad::tongue::cry::biggrin:::smile:

Her landing was cushioned by the mech hanger, which unsurprisingly bent. Using a bit of brute force I bent it back, but now it has telltale flaked paint.

The aluminium under the paint doesn't appear cracked, but I am aware that it is compromised now. My question is - how much load does the mech hanger have to take?

Even at full power is there much load on the rear derailleur? It seems to me that the top run of the chain, thus the chainrings and cassette are heavily loaded, but the derailleur just keeps the bottom chain run from flapping around.

I don't have the money to buy a new hanger this month, and am wondering if it will suddenly and disasterously snap 50km into a club run.
 
jiggerypokery

jiggerypokery

Über Member
Location
Solihull
You should be ok JRG, I was looking at this last night when I was putting a new chain on X and from what I can tell the rear mech is providing tension between the jockey wheels and the big rings (techy I know ;)) when you change up and down the gears thus moving the rear mech. You are pulling the mech obviously and the force is distributed through the mech to the hanger - the over all surface area of the joint between the hanger and the frame dissipates this force in to the frame, this force distribution is also helped by the joints and springs of the rear mech soaking it up some what. Assuming that you really haven't cracked the frame you should be ok. Having said that you are right that you have compromised the material integrity of the aluminium but to what extent you'll never know.

At full power ther should be very little load, other than the sprung tension it gives itself, on the rear mech as it is providing tension and guidence and if you follow through the line of the chain you will see that the most tension is at the load points where the chain sits on the teeth of the rear and front rings and at every pin along the top of the chain. As the chain leaves the front rings right the way through the jockey wheels of the rear mech there will be very little tension.

Not sure about shifting under load though so would ease up and then shift.
 
fossyant

fossyant

Ride It Like You Stole It!
Location
South Manchester
Don't forget alloy doesn't like being bent back - it gets stressed (ahem) - you might need a new hanger at some point - wouldn't panic too much..

Steel - not a problem - did this to one of my bikes many years ago in a crash.
 
llllllll

llllllll

New Member
Bent my 'hanger back into shape with a vice years ago. Done several thousand miles on it since, no problems.
 
ColinJ

ColinJ

Puzzle game procrastinator!
Location
Todmorden - Yorks/Lancs border
On my first cycling holiday in Spain, I met a Scottish guy whose Bianchi'd just had its hanger bent by clumsy airport baggage handlers. He was pretty pissed off about that (as one would be) but he just bent it back into position and came out with my group that first day. About 30 miles into our ride there came an agonised scream from the back of the bunch as we started to climb a steepish little hill. Bent-Bianchi owner had just changed gear and stood up and his rear mech had gone into his wheel. Result: one snapped off hanger, a mangled mech, several broken spokes, and a snapped chain xx(! It might have been because he'd bent the hanger over too far causing it to go into the spokes when he changed to bottom gear, or perhaps the hanger had snapped first and everything else happened as a consequence of that?

Between us we had enough tools and knowledge to improvise repairs which left him with a single-speed bike to ride back to the hotel. What a crappy start to a cycling holiday - he wasn't a happy chappy! However, his luck was about to change big-stylee...

(The) Robert Millar arrived at our hotel with a fleet of top racing bikes to test (Bianchi, Pinarello, Colnago etc. etc.), and also a selection of top race wheels to switch between the bikes. He was doing comparative reviews of the bikes and wheels for one of the big mags, I think it was ProCycling, and he was willing to let us borrow the wheels and bikes in return for us writing mini-reviews to help him. Best of all, our sad Bianchi owner just happened to be RM's size so all those great bikes were the perfect size for him. He got to ride a different fantastic new bike every day for a week :biggrin:!

Unfortunately, the bikes were all far too small for me... :smile:
 
barq

barq

Senior Member
Location
Birmingham, UK
I think the tricky part is getting the hanger bent back so all the gear shifts work - if you've overcome that then well done. Presumably you bent the hanger to one side (rather than forward or back) so I'd be picking my gear ratios carefully to keep a straight-as-possible chainline.

What Colin says about the devastation caused by rear mechs going into wheels is true though. I did it a year or so back when one of my MTBs clipped a fallen tree and it pushed the rear mech through my wheel - it elongated the rear triangle of the frame, destroyed an XT mech, and ripped out four spokes. Nasty. So if you have one of those plastic spoke protectors to fit behind the cassette then now is a good time to use it as a cautionary measure, because if your hanger does break you know where the rear mech is headed don't you!
 
domtyler

domtyler

Über Member
ColinJ said:
On my first cycling holiday in Spain, I met a Scottish guy whose Bianchi'd just had its hanger bent by clumsy airport baggage handlers. He was pretty pissed off about that (as one would be) but he just bent it back into position and came out with my group that first day. About 30 miles into our ride there came an agonised scream from the back of the bunch as we started to climb a steepish little hill. Bent-Bianchi owner had just changed gear and stood up and his rear mech had gone into his wheel. Result: one snapped off hanger, a mangled mech, several broken spokes, and a snapped chain ;)! It might have been because he'd bent the hanger over too far causing it to go into the spokes when he changed to bottom gear, or perhaps the hanger had snapped first and everything else happened as a consequence of that?

Between us we had enough tools and knowledge to improvise repairs which left him with a single-speed bike to ride back to the hotel. What a crappy start to a cycling holiday - he wasn't a happy chappy! However, his luck was about to change big-stylee...

(The) Robert Millar arrived at our hotel with a fleet of top racing bikes to test (Bianchi, Pinarello, Colnago etc. etc.), and also a selection of top race wheels to switch between the bikes. He was doing comparative reviews of the bikes and wheels for one of the big mags, I think it was ProCycling, and he was willing to let us borrow the wheels and bikes in return for us writing mini-reviews to help him. Best of all, our sad Bianchi owner just happened to be RM's size so all those great bikes were the perfect size for him. He got to ride a different fantastic new bike every day for a week ;)!

Unfortunately, the bikes were all far too small for me... :angry:
Click to expand...

Great story! :biggrin:
 
OP
OP
Jacomus-rides-Gen

Jacomus-rides-Gen

New Member
Location
Guildford / London
Thats reassured me a bit, thanks all.

Fossy - the hanger is Aluminium, so is a write off... just as soon as I next get paid!

It didn't bend too much, just enough to make the derailleur just skim the spokes on 23t.

So I bent it back to verticle, tuned my gears and everything runs perfectly, apart from slightly imprecise downshifting. But I always tune my gears to shift up very fast, and require more input on the way down so it feels almost totally normal.

I have checked it again after riding in London tonight - and I didn't exactly hold back, even got a few heavy handed upshifts in there :biggrin: and it seems exactly like before.

I must remember to back off properly before each shift, even if accelerating hard out of TLs.
 
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