copper as a setpost shim???
 

Does anybody know of any web-site or literature concerning the use of copper shims with aluminum frames and seatposts? My local bike shop inserted one in my seatpost and now want to charge me for removing the seized post.. I know these two metals should never be used in this way but have no ammo to proove their neglegence.. Please help me save about 200 bucks and deprive these arse scratchers of my hard earned cash! Steve from Norway

Take it to another shop and tell them what happened. Tell them you are looking for a new shop and maybe they will help you to keep your business. I would be damned if I would pay the shop that caused the issue, to fix their mistake.

Sounds like galvanic corrosion. Lots of references on the web. (Google "galvanic couples"). For a quickie, see:

http://www.mtec.or.th/th/research/fa...als.htm#table1

In particular, show them Table 2. Make appropriate Homer-esque D'Oh when you do. If they want to charge you for their negligence, find another LBS.

nice link! Here's a novel idea, they should have used aluminum.

Thanks for your help with the link. Believe it or not this is an authorized trek dealer that did it.. maybe they have something against cannondales.. I wrote to Trek about copper shims and made out I'd put it in myself. I got a reply yesterday which started: WHY ON EARTH DID YOU PUT A COPPER SHIM ON AN ALUMINUM SEATPOST..? so I guess that should make them get their fingers out of their arses! Cheers

Hahaha!! Priceless.

hahaha!!!!

definitely let us know what they say, and what they do for you since they obviously screwed up.

Lots of swearing and blaming eachother, embarrassed customers, the other bike mechanics pretending to be concentrating on their work- SO INTENTLY! Email print-offs everywhere... The nugget actually banned me from ever going back to his shop (I laughed) but I walked into the shop with no money and then cycled home.
The last thing I said was- 'dont feel so bad, youre not alone, good bike shops are hard to find'
I seem to have bad luck with bike shops, or is it really the same for everyone?
Oh well thanks for the support guys and remember, stand your ground with these smart arses &if all else fails threaten them with bodily violence :)

doesn't anti-seize grease have copper? How come you're shim siezed up if they use copper in anti-seize?

not saying you're wrong, just something I'm wondering about...

Cut up a beer or pop can and use as a shim. . . and find another bike shop!

the copper in the grease soaks up all the 'action' so to speak, so it stops the bike parts corroding together. Copper's used precisely because it reacts so strongly to alu but its obviously well lubed in grease so has no ill affects... I only learned this myself because of what happened to me

For galvanic corrosion to occur, the dissimilar materials must be in contact in the presence of a suitable elctrolyte. Water works, so does sweat, etc. The grease prohibits water, etc from entering the interface between the two. That's what grease does best.

Cervelo shims all their seatposts with a brass part.

Since brass is 85% copper and they sell their aluminum frames with aluminum seatposts shimmed with this part I don't think that they did anything that a leading maufacturer does not do as standard practice.

See the link below for the part I am referring to:

http://cgi.ebay.com/ws/eBayISAPI.dll...113021493&rd=1

Does that mean that Cervelo is negligent? Or maybe you are wrong to blame the shop.

Not sure what's going on with the brass shims there.. but I got emails back from Bontrager, Trek, Park tools and Cannondale advising me that copper was the wrong material for shims with aluminum frames and seatposts

Congratulations on turning your bike into a battery.

it was only in the frame for a few weeks & it was a brand new raceface post. If you want to take a look click on http://www.beanpix.com/image/6516079...49C6BE34789F64 Imagine how much it corroded on the inside of the frame on the raw unfinished alu?! (&in just a matter of weeks)

Well, brass is different stuff. If you mate copper pipe to steel you will get galvanic corrosion, but stick a brass nipple betwen the coppper and steel and all is good.

brass is an alloy, so the copper is "bound" and thus prevented from the galvanic process as others have alluded.

So, to answer your questions; "No" - Cervelo isn't negligent, "No" he wasn't wrong to blame the shop - they were *definitely* negligent!

Also, the copper in the antisieze is in suspension which means that the particles are dispersed and can't make a circuit. A sheet of metal is, by definition, a conductor so that galvanic action can occur.

Bottom line: Antisieze good, sheet metal bad.

Stuart Black

Over the short run this may be true but over a period of years, in a home water system, the pipes will corrode shut. Trust me, I had to replace all of the pipe in my house because some bonehead put galvanized/brass and galvanized/copper together.

In a bike application however, there is little water to mobilize the electrons so the galvanic action would be much slower. It's probably the tin in the brass that slows the reaction down.

Stuart Black

Looking at the table and considering the discussion elsewhere in this thread, I'd be leary of using brass also. Brass has the same galvanic potential as copper according to the table. Overall it's just not a good idea to mix dissimilar metals without something to serve as a dieletric insulator.

Stuart Black

I would just add the observation that when copper oxidizes you get that blue powdery layer, and, when aluminum oxidizes you get that nice white powdery layer, and when steel oxidizes you get that nice red powdery layer - but (voila!), when brass oxidizes (ok, I know there is no such thing as "brass oxide", so please don't even go there), you pretty much just get a change in the color of the surface and you do NOT get that nasty powdery oxide layer you get with other metals. That's one of the really nice qualities of brass. Bronze is even nicer. That being said, I'd guess that anyone who was ever in the Army probably despises brass, for the obvious reason ;)

That is standard procedure. It'll rot out alot quicker without the brass nipple.I've been there becasue a bonehead used a galvanized nipple when it should have been brass,cuz code allowed it at the time and he could save a few cents. Galvanized will rot out no matter what anyway,cus it isn't galvanized on the inside where it really matters. You could have also had deposit buildup unrealated to galvanic action. There is a good reason galvanized is no longer used in current construction.