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Discussion Starter · #1 ·
I installed a C'dale wind carbon seat stem on my Rush and I'm getting a good 1.5 inches of slippage after a 20k XC ride (with some technical trail). The collar is as tight as I can get it with my hands... I don't want to crack the carbon or bend the seat tube by over tightening. This being said the carbon is now scraped / gouged a bit from the slipping.

1) any installation tricks to stop the slippage?
2) is the seat post too damaged to be safe now? (I'll post photos later)

Any help would be appreciated.

PT
 

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LA CHÈVRE
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First, make sure there is no grease on the seatpost/inside the seat tube. Some grease can eat the resin that hold the carbon fibers together. It also makes the post slip more.

Second, the Wind carbon is in fact a thin wall alloy post reinforced with a thin layer of carbon (look in it from the bottom, you can see the alloy). It is quite light but also strong, so it should be fine.

Do you have a bolt or a quick release to hold it? If you have a quick release and that it's a Cannondale, I would suggest you change it. Cannondale QR seat collars are not so good... probably the worst part on a Cannondale and by far. A Salsa Flip Lock is among the best, Hope also makes good ones... But if you have a bolt-on collar and it still slips when tightened as hard as you can... well, see point number one.

Third, seatposts get scratched, it's just the way it is. Don't worry about it. I lower mine when going down crazy, steep, long downhills so it is scratch a lot but still safe, the marks are just in the clear coating that protects the carbon.
 

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Go Salsa

PT, I have a brand new Rush w/carbon components, and I had to replace the factory brand collar also because it kept allowing post to slip down. Wish I had replaced it before I had started riding to avoid scratches, oh well. I bought the Salsa quick release and bolt-on style. The Salsa clamps are wider (taller?) so it clamps more of the seat tube. I have not had any slipping problems with the Salsa quick-release so I haven't even bothered to try the clamp-on style.
 

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Discussion Starter · #4 ·
Dan... Thanks for the feedback... yes it is the stock C'dale clamp.

I'll look into upgrading the clamp as my first option, and good to know about the alloy make up of the Wind post... I didn't want to end up with this thing stabbing me in the thigh or the butt.

Here are the pics of the damage.

PT
 

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LA CHÈVRE
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pthorne said:
Dan... Thanks for the feedback... yes it is the stock C'dale clamp.

I'll look into upgrading the clamp as my first option, and good to know about the alloy make up of the Wind post... I didn't want to end up with this thing stabbing me in the thigh or the butt.

Here are the pics of the damage.

PT
By looking at your pictures, I can say two things:

1. The damage is cosmetic only, don't worry.

2. You do have the crappy collar I was talking about. A Salsa has a steep price for such a small and simple component, but it's the best quick release I have found to date... Here is mine, holding the same post firmly in place:

 

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Discussion Starter · #6 ·
That's good news....

I'm glad the post strength is not compromised. It would have been an expensive few rides.

I'll try the LBS's in my area to see if they carry the Salsa clamps.

Thanks for the feedback
 

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Drink...sleep
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pthorne said:
Here are the pics of the damage.

PT
I just noticed, and correct me if I'm wrong, but isn't your seatpost too high up, stuck too far out of the frame? It's past the max line, and with only a tiny portion inside the seattube, a bad crash could damage the frame (with the seatpost not clearing the lower tob tube weld).
 

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I was nervous about this as well when I borrowed a Rush a couple of weeks ago. The lower tob tube weld is actually quite a bit higher than normal frames, so when one measure 10 cm down. You actually clear the lower toptube weld quite easy :)
 

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Discussion Starter · #10 ·
I've been riding it about a half inch higher that the max height. This still allowed for around two inches of post secured in the seat tube. Some of the gouges / scratches happened inside the seat tube (along the open part of the tube) which make it look like I had it up way too high. I hope the half inch isn't a real threat to my health. :eekster:
 

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pthorne said:
I've been riding it about a half inch higher that the max height. This still allowed for around two inches of post secured in the seat tube. Some of the gouges / scratches happened inside the seat tube (along the open part of the tube) which make it look like I had it up way too high. I hope the half inch isn't a real threat to my health. :eekster:
I would really find a longer post. You are risking a broken post, damaged frame and injury. Also if if does damage the frame it will be out of warranty. You said it's only a half inch but this is a 20% reduction in insertion.

Also make sure you use grease despite what someone else said above. Without grease your risk corrosion in the interface which will bond your post to the frame and have you using a hacksaw to get it out. Particularly now that you have scratched the carbon post a bit. Carbon and aluminum are very prone to corrosion when in contact. If you can't get the post tight the problem is in the clamp not the grease on your post.
 

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If the bottom of the seat post clears the bottom top tube weld everything is fine. This is a rule the pro bike mechanics use. If your gouges/scratches goes through the outer clear coat and into the cf matrix then you should be nervous. The clear coat is a protective layer that is supposed to take a beating... And since you haven't crashed, there really isn't a slight chance of actual damage to your seat post if only the clear coat have been scratched and there is no damage to the matrix.
 

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pedaler845 said:
.02~My RF Next SL carbon post instructions say clearly no lube.
Your choice but call up Cannondale and they will tell you to grease the seatpost. The ID of the seat tube is bare aluminum (no plating, no paint). So you run the thing dry, it gets wet, starts to corode and the resulting oxide takes up more space then the alumium it replaces. This basicly shrink fits your post into the frame. I've been the shop guy with the hacksaw cutting the $100 post out of the $5000 road bike due to lack of grease.

But like I said it's your bike.
 

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LA CHÈVRE
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raelx said:
Your choice but call up Cannondale and they will tell you to grease the seatpost. The ID of the seat tube is bare aluminum (no plating, no paint). So you run the thing dry, it gets wet, starts to corode and the resulting oxide takes up more space then the alumium it replaces. This basicly shrink fits your post into the frame. I've been the shop guy with the hacksaw cutting the $100 post out of the $5000 road bike due to lack of grease.

But like I said it's your bike.
Not if it's a carbon post. Carbon posts will not bond to the frame but the grease can attack it and make the post weak...
 

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Not to belabor the point but I just cut a carbon post out of a Six13 last month.

It's not the post that oxidizes, but the inside of the seat tube. Also the grease thing is urban legend or a hangover from the first days of thermoplastic composites. Modern epoxy resins are fine with grease and oils.
 

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Discussion Starter · #19 ·
As a follow up to the original question...

As I was unable to find the Salsa clamp in time for my race this past weekend the tech at my LBS suggested using a spritz of water and a sprinkle of climbers chalk on the seat post. I couldn't get chalk in time so simply used a tiny bit of fine dirt instead.

I rode the bike over 80km this weekend (24hr relay) and the post didn't budge a millimeter. Don't worry this is only a temporaray solution... but effective if all else fails and you need a quick fix. I've ordered the Salsa clip on line.

As for the lubricant debate, this one I'll leave up to the experts... in my personal case I'm switching between my carbon and aluminum post often enough (weekly) that corrosion hopefully wouldn't have enough time to take hold if it were an issue.

PT
 
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