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I were wrong about those bolts

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Started 6 years ago by I were right about that saddle
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I were right about that saddle
Member

Just adjusting my fancy German Magura HS11 hydraulic rim brakes and snapped both of the caliper clamp retaining bolts. This is very irritating.

I know how to use a Torx key. I have mechanical sympathy. But they're both broken and I have no rear brake. There's no way on earth the stumps of the bolts are ever coming out of the clamp bodies unless I dissolve them out in acid. I said a startlingly pyrophoric combination of crude words when the second one went and I hope the neighbours didn't hear.

I suspect the components were assembled without anti-seize grease. That will teach me. Strip and rebuild new components to your own satisfaction before fitting.

Hopefully I can get a spare clamp from them rather than a new brake. I'll be quite agitated if I have to replace the whole thing.

Posted 6 years ago #
Greenroofer
Member

How annoying. I have a set of those reverse thread screw extractor things that I once bought from Screwfix on a whim but have never found a use for. Happy to lend if that will help.

I think you'd need to drill a hole in the remains of the bolt...

Posted 6 years ago #
I were right about that saddle
Member

@Greenroofer

That would be worth a try if you have a small one? They're weedy M4 bolts. Nothing ventured nothing gained. PM me a suitable time and day and I'll spin by!

I thought I'd better bleed my spongy front brake given that I've now no rear. Did that, lovely job, put the caliper back on and hauled the thread on the alloy post. Rats, but I'd been expecting that to happen. It's magnesium and about as hard as old cheddar. The lower one went almost immediately and was fixed with a Helicoil inserts. I fitted an insert to the second hole and proceeded to strip the thread on the bolt. I seem to be going through a destructive phase. Found another bolt and stripped that too. With a torque wrench.

I'll get proper bolts tomorrow and make some fiber washers to stop the caliper wandering around quite so readily. Ho hum.

Posted 6 years ago #
Ed1
Member

I wrecked the nut on my rear brake today the avid bb5 adjuster nut had ceased as had not adjusted in 3 months with metal brake pads almost maintainer free so took a 10 inch wrench to help turn the allen key not a wise idea. Wonder if my revolution is on its way out, as last week I went to cycle to Callander and the seat bolt snapped after an hour cycling, metal fatigue. Then had to take the train the rest of the way. Cycled down from callander ok then on the way back chain snapped just before bridge. Then the next day derailleur played up. Then the free wheel started to give up still works just enough to cycle.

Posted 6 years ago #
urchaidh
Member

If you are going to try and drill them out, start soaking them in penetrating oil now and as often as you can.

Best of luck.

Posted 6 years ago #
I were right about that saddle
Member

@urchaidh

I did and have done just that, cheers. They are now drilled. I also put them through a couple of cycles of heating in a gas flame and quenching in water.

There will be great joy and feasting if @Greenroofer's screw extractors can overcome the remaining corrosion.

Posted 6 years ago #
I were right about that saddle
Member

Alas @Greenroofer's screw extractors could not do the business. The bolts were just too small and the act of screwing in the extractors caused them to flare, wedging them even tighter than before. So I drilled the bolt stubs out and re-tapped for an M6 screw instead. Had to buy a new set of drills after finally accepting that the old set are blunter than a drunken Yorkshire-man.

In the process I discovered another mistake I've made that is horribly subtle and due to one tool getting into the case for another tool. Ho-hum. It shall also be fixed by hook or by crook.

Posted 6 years ago #
Tulyar
Member

Got several clamps for the cylinders, having used HS33 on the Brompton since 1997 (when the levers were straight off a motorbike) - pictures of what you've broken?

Posted 6 years ago #
I were right about that saddle
Member

Pictures!

Posted 6 years ago #
hunnymonster
Member

Hopefully you're going to reassemble with some copper grease to prevent it recurring?

Posted 6 years ago #
crowriver
Member

Either IWRATS and Ed1 are possessed of superhuman strength, like characters from a superhero epic comics series; or they just don't make bike components like they used to.

Suppose there's a penalty to be paid for lighter bikes that are easier to get up hills...

Posted 6 years ago #
I were right about that saddle
Member

@hunnymonster

Oh yes. I always do when I assemble, these were box fresh and I assumed Magura had done the business. They hadn't.

@crowriver

It shouldn't be physically possible to snap a bolt with a key like that. It's clear that some electrochemical skulduggery has gone on here, welding the bolt at one end and eating it at the other.

Posted 6 years ago #
I were right about that saddle
Member

You'll be relieved to hear that I now have rear brakes. Bid of bodging required due to a tiny drilling error. I do wish I had a pillar drill. The two year old oil in them was utterly manky as well - it was actually black.

Look close and the right hand clamp doesn't quite line up which is shoddy.

Shiny zinc plated M6 bolts in place of the oxide finished M5 ones, which will rust in due course. Copper grease aplenty.

If anyone does have any Magura cyclinder clamps in their spares box.....

Posted 6 years ago #
crowriver
Member

"It's clear that some electrochemical skulduggery has gone on here, welding the bolt at one end and eating it at the other."

Perchance the mischievous Norse god / superhero character Loki up to no good again?

"Copper grease aplenty."

Hmm. Are the calipers/clamps steel or alloy? If the latter, then copper grease will accelerate corrosion (due to the electro-conductive properties of copper), as the bolts are steel, right? Plain brown or white lithium grease may be better in this instance...

Posted 6 years ago #
I were right about that saddle
Member

If the latter, then copper grease will accelerate corrosion (due to the electro-conductive properties of copper)

The modes of bimetallic and pitting corrosion are very complex and well studied. It's a subject I know a little about and I can't think of a single mechanism whereby the presence of colloidal copper in grease would accelerate any of them.

The copper in copper grease is a release agent. You wind up with a thin layer of sintered copper between the surfaces of the components whatever they're made of.

There is a proper metallurgist on this forum who may add more.

Posted 6 years ago #
gembo
Member

Was this all about back brakes?

Posted 6 years ago #
I were right about that saddle
Member

Do you like circuses, @gembo?

Posted 6 years ago #
crowriver
Member

---

on things that are likely to get the oxide scraped off (i.e. aluminium screws in a steel thread) then you should use lithium* grease instead. A few years ago I made the mistake of putting copper grease on the aluminium idle screws on my car's carburettor which had steel thread sleeves. They were seized within a week and I had to get the impact driver out on them.

Leaving aluminium/steel in bare contact will definitely lead to seizing though. If in doubt, use lithium grease, but copper grease is fine for almost anything you'll come across on a bicycle.

* lithium grease doesn't react because the lithium in it is already reacted. Copper grease contains unreacted particles of copper.

---

From:

http://www.bikeradar.com/forums/viewtopic.php?t=12698017

Posted 6 years ago #
gembo
Member

@IWRATS, yes as you know from the early doors DVDs I do like circuses but not temporary traffic lights

My new early doors show is Two Doors Down which is Rab C transferred to Giffnock if you know your outlying posh bits of Glasgow (note, not posh)

Posted 6 years ago #
I were right about that saddle
Member

@crowriver

Grease is an emulsion of of a surfactant and an oil. Bathroom soap is one surfactant. It's largely sodium stearate. Lithium grease could have lithium stearate as the surfactant. Molybdenum grease has moybdenum sulphide as the surfactant. There are loads of other ones.

Copper grease contains a soap, but it isn't copper stearate. It could well be lithium stearate. What it does have is colloidal copper added to a rather fluid classic grease.

If you tried to use a grease with colloidal lithium (and I can't think how you'd even make that) you would quickly have a fire on your hands.

It's possible that the bikeradar guy may not quite know what he's talking about. Copper grease is commonly used in automotive brakes where bimetallic corrosion is a huge problem. It is an inert release agent designed to stop components sticking together rather than a lubricant. I have no concern at all in using it between steel and aluminium alloy pieces.

Posted 6 years ago #
I were right about that saddle
Member

I quite like circuses, but when I was little the animals were sad and the clowns were drunk and I got a flea.

And now I'm thinking about making grease with colloidal gold in it as the ultimate non corrosive release agent.

Posted 6 years ago #
hunnymonster
Member

Yep most "grease" is actually lithium soap (not as good for your hands as Fairy liquid and absolutely cack for cleaning stuff) as IWRATS says with various goodies mixed in Molybdenum Disulphide being a popular one (Molyslip) or the elemental copper in Copperslip (always referred to as slopperkip here)

Posted 6 years ago #
Frenchy
Member

@IWRATS - a surfactant dispersed in a liquid isn't an emulsion. You need two immiscible liquids and something to prevent separation (normally a surfactant) to make an emulsion.

Posted 6 years ago #
Greenroofer
Member

I'm slightly concerned that I may be the 'proper metallurgist' that IWRATS was referring to. All my proper metallurgy was 25 years ago, and by the end had a very narrow focus on obscure techniques for high-productivity continuous casting of aluminium beverage can alloys. Since then I've worked in a bank. I'm going to sit this one out...

Posted 6 years ago #
gembo
Member

The smell of the crowd, the roar of the greasepaint. Every circus I have ever been at has sad animals, drunk clowns and you get a free flea

Posted 6 years ago #
chdot
Admin

In your ear?

Posted 6 years ago #
gembo
Member

I did get a row off a rubbish clown once for trying to get in the ring, and a kick from a burroo.

Clown smelled strongly of drink. Mule v bad tempered.

Posted 6 years ago #
neddie
Member

You need to be careful if putting grease of any sort on bolts, to avoid over-tightening them. Especially if using a torque wrench - the grease will allow the torque and hence tension in the bolt to become much higher than it should be.

Torque wrench settings become null and void if grease is used. Particularly important for the wheel bolts of 5 - 8 seat combustible metal boxes*

Fleas are killed easily by putting them on a bar of soap, or maybe some Molybdenum Disulphide if you fancy giving them a luxury death.

* ©️ Bob Gunderson

Posted 6 years ago #
I were right about that saddle
Member

@Frenchy

Can you think of a better term for an oil dispersed in a soap? I can't. It's not a solution, it's not a colloid. I consider it to be an emulsion as the two components are immiscible fluids physically distinct from each other and microscopically divided.

Posted 6 years ago #
Frenchy
Member

I'd just call it a solution, to be honest. But not quite my area of expertise (certainly not in real applications, anyway).

I'm maybe misunderstanding too, I was assuming that the surfactant and the oil were miscible. Is the oil the majority or the minority phase? I'd call it an emulsion if only one of the passes was continuous.

Posted 6 years ago #

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