Impressive but expensive breakdown

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TomTurner
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Impressive but expensive breakdown

Postby TomTurner » 15 Jul 2011, 2:15pm

Hi All

Myself and a Mate were riding around the Elan Valley yesterday as we have done hundred times but yesterday was sightly unusual in terms of the breakdown my mate suffered:
IMG_0222.jpg
IMG_0223.jpg


As you can see the rear de-railer bolt has sheared and that brought the de-railer up and over the cassette. It happened as we were climbing (it caused the back wheel to lock up which would have been nasty if on the decent) He had just changed gear as the fail occurred but I didn't sound like a poor gear change however he was trying to put it into the big chain ring, which isn't the best plan on any climb....

I was wondering if anyone has ever seen this before or have any ideas on the cause? (the forces involved must have been huge!)

Regards,

Tom
"It never gets easier, you just go faster." Greg LeMond

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Mick F
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Re: Impressive but expensive breakdown

Postby Mick F » 15 Jul 2011, 4:49pm

I've never seen that before

Is the chain ok? If it is, it can only be that the mech came unscrewed or broke. It the bolt still in one piece?

If the chain and the bolt are still "whole", I'd guess that the rear mech was loose in the first place. ie the bolt was unscrewing. Consequently, the mech just stripped out the remaining few threads.
Mick F. Cornwall

iviehoff
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Re: Impressive but expensive breakdown

Postby iviehoff » 15 Jul 2011, 4:57pm

I've had derailleurs self destruct and end up in roughly that position a couple of times, but not actually shear out of the derailleur hanger.

gilesjuk
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Re: Impressive but expensive breakdown

Postby gilesjuk » 15 Jul 2011, 5:52pm

If something jams the dérailleur it tends to get ripped to pieces.

It's probably a good idea to not spend too much on one if riding off road.

TomTurner
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Re: Impressive but expensive breakdown

Postby TomTurner » 15 Jul 2011, 8:00pm

Hi,

I think the chain will need to be replaced too, it was VERY twisted. It is so strange as it isn't as if he had been mistreating the bike and is fairly new. Plus as you can see is was a Campagnolo so wasn't exactly cheap gear that failed.
And as it is a road bike there isn't that much to get caught in the de-railer...

How my mate managed to keep it up right is a mystery to me. :shock:

TT
"It never gets easier, you just go faster." Greg LeMond

gilesjuk
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Re: Impressive but expensive breakdown

Postby gilesjuk » 15 Jul 2011, 8:09pm

Even on the road a twig can get flipped up and get jammed in there.

Someone on a monday night group ride around here got his carbon frame written off because of a bit of exhaust pipe hitting his frame.

It's still worth keeping the old mech parts, they may be handy for future repairs.

Big T
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Re: Impressive but expensive breakdown

Postby Big T » 15 Jul 2011, 9:30pm

This happens a lot in cyclo-cross races. It's not unusual for several people to lose rear mech's in this fashion in an hour long cross race, especially if it's muddy. My wife managed to rip 3 rear mechs off in 12 races last season.

The gear hanger is designed to be a weak point to save damage to the rest of the frame.

It'll probably need a new rear mech, new hanger and possibly a new chain if it got twisted. Hangers range from £10 to £25 depending on the frame.
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jb
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Re: Impressive but expensive breakdown

Postby jb » 16 Jul 2011, 1:01am

If he was trying to force it onto the large chain ring whilst climbing then it probably grabbed the chain and pulled it round the ring, thus pulling out all the slack and then pulling the gear changer off.
Cheers
J Bro

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Mick F
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Re: Impressive but expensive breakdown

Postby Mick F » 16 Jul 2011, 6:53am

That sounds right, but it assumes the chain wasn't long enough to go to Big Big.

A chain MUST be long enough for that situation. This looks like a salutary lesson.
Mick F. Cornwall

TonyR
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Re: Impressive but expensive breakdown

Postby TonyR » 16 Jul 2011, 10:23am

Was it a breakaway derailleur bolts that is designed to shear there to save the frame if something goes amiss with the derailleur or chain.

rower40
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Re: Impressive but expensive breakdown

Postby rower40 » 16 Jul 2011, 1:21pm

Big T wrote:This happens a lot in cyclo-cross races. It's not unusual for several people to lose rear mech's in this fashion in an hour long cross race, especially if it's muddy. My wife managed to rip 3 rear mechs off in 12 races last season.


This is a possible reason for the marketing of the Genesis Day-One Alfine as a cyclo-cross bike. Disk brakes, 8-speed hub gear.
I've got one, but I've fitted skinnier tyres, mudguards and a rear rack, and use it as a commuter bike. Will be making an appearance on the Dun Run tonight. Look for (as described on the other forum that's down at the moment, which is why I'm here) "a gay barber's pole".
"Little Green Men Are Everywhere... ...But Mostly On Traffic Lights."

Tony1968
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Re: Impressive but expensive breakdown

Postby Tony1968 » 19 Jul 2011, 1:21pm

I reckon my next door neighbour has spent more on mechs in the past few years than I did on my Rohloff!

hamster
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Re: Impressive but expensive breakdown

Postby hamster » 25 Jul 2011, 3:01pm

Looks to me as though a foreign body or the rear mech was badly adjusted and stuffed the chain between the spokes and cassette. That than dragged an armful of chain and took the rear mech with it, finally tearing the mech from the hanger.

I have had a similar prang as GilesJ says, where a twig does the same thing.

pete75
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Re: Impressive but expensive breakdown

Postby pete75 » 25 Jul 2011, 6:18pm

rower40 wrote:
Big T wrote:This happens a lot in cyclo-cross races. It's not unusual for several people to lose rear mech's in this fashion in an hour long cross race, especially if it's muddy. My wife managed to rip 3 rear mechs off in 12 races last season.


This is a possible reason for the marketing of the Genesis Day-One Alfine as a cyclo-cross bike. Disk brakes, 8-speed hub gear.
I've got one, but I've fitted skinnier tyres, mudguards and a rear rack, and use it as a commuter bike. Will be making an appearance on the Dun Run tonight. Look for (as described on the other forum that's down at the moment, which is why I'm here) "a gay barber's pole".


I don't think disc brakes are allowed in cyclo cross events.

BigFoz
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Re: Impressive but expensive breakdown

Postby BigFoz » 26 Jul 2011, 10:33pm

Rules were changed recently to allow discs. This coming season will be first complete season they're allowed - hence the sudden proliferation of Disc equipped CX bikes.