Homebrew01

How do I get mine out of my CAAD 8

eja_ bottecchia

Those are cool!

Andy Somnifac 

How can carbon fiber and aluminum lead to galvanic welding when there is no metal in the CF? Not saying a carbon post can't get stuck (I've certainly seen many types of material seat posts stuck in all sorts of frames), but it's not due to a galvanic weld between the seat post and frame.

topflightpro

Aluminum and Carbon don't like each other, and the materials react chemically when they touch. It's more commonly referred to as galvanic corrosion. You can find lots of info on this if you google aluminum carbon galvanic corrosion.

I have had carbon posts stuck in aluminum frames. It's a PIA to get them out. WD-40 and lots of torquing eventually got the post out. It's less of a problem if the post has a good layer of clear coat on it.

As for the advantages of carbon over aluminum, I don't really know any. I have Thomson on one bike and a carbon post on another and I can't tell a difference.

Andy Somnifac 

Hmm. I've always read about galvanic corrosion re: two dissimilar metals with different voltage potential. Even the leading paragraph of Wikipedia states:

"Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact and immersed in an electrolyte."

Guess you learn something new every day.

topflightpro

I am having an issue with galvanic corrosion on my Cannondale System 6. It's unpainted and the carbon and aluminum are corroding. It's reached the point that the clear coat is flaking off and looks like crap. Oh and sweat and sports drink act as the electrolyte.

Though the local Cannondale rep told me the frame was OK, I did reach out to some material science professors at local universities about it. Their general statement was that yes, galvanic corrosion between carbon and aluminum is a well known problem, and that folks in the aerospace and marine industries take special steps to make sure any aluminum and carbon connections are well prepped to avoid any corrosion and reduction in the lifespan of airplanes and boats.

Commodus

I can feel a bit of give from my carbon post. It's not huge, and I have a very lightweight post with a ton of setback on an alu frame so really I have the ideal situation to notice it.

Jed19

Galvanic corrosion should not be an issue if you are on top of your regular and routine maintenance. I always take my Thomson seatpost out of my carbon frame every three/four months or so. I wipe the seatpost down, wipe the inner sleeve of the seat tube, apply carbon prep and reinstall. Never had an inkling of a corrosion problem/issue.

qqy

If your seatpost is getting stuck you guys are terrible with maintenance. Pull the post out every year (more if you're especially sweaty). Reapply grease to a metal post or carbon paste for a carbon post. It will never get stuck. Use electrical tape to mark the insertion depth.

A carbon post does feel slightly nicer, and is generally lighter than a alu one, and can be stiffer. However a Thomson masterpiece is close competition. I ride a fairly heavy K Force post and it's notably more comfortable and stiffer than the alu post it replaced.

Dunbar

I like my $40 Nashbar carbon seat post. Made a very noticeable difference in smoothness when I swapped out my alloy post (on my carbon Giant OCR.) With the two bolt (Thomson-style) design makes angle adjustments a snap. It's a ridiculously good deal but not that stylish looking.

knobd

I got a cheapo Ascent carbon seatpost off of Nashbar. I actually feel a difference on large bumps but not with the buzz. Probably not worth it but didn't spend much to start with.

Racer Ex 

Not all carbon posts feel the same. Most aluminum posts do.

Some carbon posts are actually carbon wrapped aluminum BTW.

If you use a carbon post in an aluminum frame use a waterproof grease. Carbon paste doesn't prevent moisture from setting up the cell that was referred to earlier. I've had a carbon post on my wife's bike for 6 years. Loosen the clamp and it come right out.

Essex

I am wondering if some type of dielectric paste (to reduce galvanic corrosion) would work vs carbon paste? This silicon lube is used in scuba tanks to prevent corrosion between steel valve cylinders and aluminum ally tank threads. The stuff id pretty viscous:

https://www.dowcorning.com/applicatio...t.aspx?r=393en

Cheers,

Essex

tagaproject6

Get one if you want one. If not, then don't. Any justififcation is valid.

merlinextraligh

Odds are you can save as much weight as going to a CF seatpost for free.

The weight on your seatpost is for a 400mm post. Most road bikes do not need a 400mm post (heck it used to be standard for road seat posts to be 250mm) So cut your seat post to the lenght you need extended, plus some room for future adjustment, and a generous amount of insertion ( a bit more than the minimum). Depending on your height, and your fram, you likely can cut 100 mm off that seatpost.

Totoboa

I am at work and my rig is at the house. Anyways, I would like to chop my alu post. It's the stock real cheapie that came on my Windsor Wellington 3.0. I have removed the post and seat before to weight them here at the State testing Lab. I don't recall seeing any marks of any kind on the post.

1.) How much embedment should I leave on the post when I chop it ?

2.) The stock post is a single bolt design. I think I gather from some of the above that a 2-bolt system allows seat inclination adjustability. Is this true ?

FWIW, my $0.02 about upgrading my inexpensive aluminimum frame Sora STI component bike; I will cut the seatpost/seat cobined weight nearly in half by switching out my seat (done, $19 for a used Nash including shipping EBAY) and the carbon seatpost. Almost a POUND for well under $50 total.

Anyways, thanks if you can answer.

bigbadwullf

Sorry. Pet peeve of mine. It DAMPS vibration. Or it helps vibration DAMPING. To dampen something is to wet it . Carry on

merlinextraligh

General rule of thumb is that the minimum insertion is at least 2 times the width of the seat tube diameter.

Your seat post should have a minimum insertion mark. Measure from that mark to the end, and that 's the distance you'll need to leave below where your seat post enters your frame. Add an inch (maybe a bit more if you don't have your fit dialed in.) and you'll have a margin for error and adjustment.

Virtually all seatposts, one or two bolt designs allow you to adjust the incline of the seat, some of them allow you to do it easier than others.

gregf83 

Merrian-Webster disagrees with you:

Definition of DAMPEN


transitive verb
1
: to check or diminish the activity or vigor of : deaden <the heat dampened our spirits>

jdon

Unfortunately, both are correct. Drives me crazy though, when the aircraft Yaw Damper is referred to Yaw Dampener...

jdon

The only reason to have a CF post is to shut your wife up when she claims child birth is the most painful experience. Surely plucking CF slivers out of your ass is comparable. That is why it is called assplode.

pallen

I had the same question when I first saw mention of it. After some searching around on the interweb tubes, it appears to also happen with Carbon. I dont know if its the carbon or the Polymer its bonded in thats the issue, but its real.

Totoboa

Yer splitting hairs my friends.

The English language is extremely rich and diverse. That's what my foreign born co-workers tell me. Nothing else is close. If we dumb it down, like we would if we were sitting in a bar in public, so we don't argue, we could probably agree that the definition of the term corosion originally applied to metals. Like when I dropped brass BBs in my dad's Grumman Aluminum canoe and got a tongue lashing and a technical beat down about dissimilar metals. The process was defined by the conditions, the metals. Fast forward 40 years, from aluminum aircraft to composite ones, or in this case, bicycles, and you have the same process. With the composites etc. Same process, the materials have changed a little. Ask the Iraqi air defense over Bagdad

So, a newer definition, if anyone bothered to update the dictionary, would update the word to encompass the engineering newness.

Gawd, that took 6 minutes including spell chek.

Dunbar

Apparently "conversate" is now in the dictionary.I'm not sure I'd consider that progress.

Andy Somnifac 

Indeed. Like I said, learn something new every day.