dimethi

Hey all,

I bought a used CF frame (I know, I know) that was advertised to be in good condition. When I checked it out in person, everything seemed fine. No scratches, cracks, or chips anywhere.
...then I got home, and took off the seat clamp. It looks pretty bad--the black stuff is grease that got through the cracks in the clear coat.

I can't tell if only the clear coat is cracked, or if the carbon underneath is toast as well. (I did the coin test, and everything sounds fine.) The crack in clear coat goes all the way to the top of the tube-- no cracks below the paint chip.

Took it to a local Giant dealer, he said it was "very concerning" but admitted he wasn't a carbon expert. Any further input from you guys would be great.

Thanks for your time.

Picture 1 | Picture 2 | Picture 3 | Picture 4

Picture 5 | Picture 6 | Picture 7

FBinNY 

All your photos are so close up that I can't get a sense of scale or the big picture. However if the damage is limited to the clamp area in the classic location near the top of the mast, then it probably doesn't matter. As long as the post is inserted well below the damaged area, say a minimum of 3 inches or so, then the clamp area is non structural, so there's little risk of failure,

I'd clean it up, seal it with something suitable, and ride the bike.

dimethi

Thanks for your reply! The damage seems to be where you describe it, although I'm not sure what you mean by inserting the post past the damaged area-- it's an integrated seatpost.

Apologies for the amateur photography--I took a few more photos to help better scale: Image 1 | Image 2 | Image 3

FBinNY 

I see. That may change things, since there's no sleeve inside tube buttressing as in a conventional arrangement.

I can't tell from the photo how the clamp assembly affixes to the mast, and in a situation like yours the devil will be in the details.

I'd have to see it in person, and see how it works, where the stress points are and the exact nature of the damage. Then factor your weight and make some kind of judgement call.

BTW- this and ones like it aren't my favorite designs because they increase the likelihood that if/when any failure happens, it'll be to the expensive part (the frame) and not a less costly replaceable part.

dimethi

I'll try explaining as best as I can, though I agree having it in front of you would be much better.

The clamp is designed to be a fair amount in the frame (35mm minimum insertion to a maximum of 70mm). There is only one screw at the bottom that clamps it in place, which I took a picture of: Picture 1

The screw is directly center of indentation/black spot when it's 70mm in. Image 2 in my last response shows it lined up from the side view. Here's a head-on picture: Picture 2

I'm 150 lbs, and I unweight myself from the saddle pretty frequently, although I wouldn't want to do it to save a suspicious frame.

FBinNY 

As I guessed, the clamp assembly slides down over the frame (not in). It.s a design which stresses the frame immediately below where the clamp sits, so that's an area to be watched. You have to hope that the engineers knew the implications and reinforced the mast adequately. They've done so with forks for years, so no reason they couldn't here.

Touch it up and ride, but pull it apart for inspection on some sort of regular basis. You might also send photos to Giant and ask what they think.

Lastly,you might carve an internal plug from wood, and glue it inside the mast as a back support in case the CF fails. It should be at least 5" long and centered over the bottom of the clamp. Wooden dowel safety nets were SOP in steel forks for decades until higher strength steels and butted tubing ended the need for them.

dimethi

Okay, will do. Thank you so much for your insight FBinNY.

If anybody else wants to chime in with their thoughts, please feel free to chime in!

hueyhoolihan

apologies, but i can't make heads nor tails of the seatpost clamping arrangement. although you've supplied plenty of pics.

anyway, i would be wanting to look at whatever part of the frame or seatpost or seatclamp that bears on the part of the frame that shows distress. it could help in assessing the extent and cause of any damage.

is there a stock pic somewhere on the internet of a bike like that as a whole?

did some digging...

is it something like this?



if so, i'm no help, because i would suspect the interface between the seatmast and the clamping mechanism, for want of a better word, and i've never had one in my hand, and so have no idea how they are secured to the mast.



better pic?

if it were mine, i would probably take some steel wool to the mast and clean it up a bit then take a close look, even to the point where i might risk removing the shine. taking care to not go below where i intended to set the clamp. then look inside that complicated looking clamp and determine if all was well inside. looking closely for anything that protruded unnecessarily. i would also assess the thickness of the mast's CF and decide whether or not it satisfied my safety concerns. shearing it off fore/aft would take a bit of doing i would think.

BTW, i've got a number of inexpensive full carbon saddles. one has a 1 inch crack up the side. i still ride it, and have been for a number of years now. it hasn't gotten any worse, as far as i can see. i'm about 160 lbs.

i also noticed, in one of the closeups, that i magnified even further, it looks as though the previous owner may have done a little DIY with some type of transparent plastic "shoe goo" type stuff on the slightly damaged area that where the clamping mechanism bears. but i suppose i could be imagining it.

dsbrantjr

I love my old steel bikes.

Andrew R Stewart 

The OP's clamp sems to have the binder slot and bolt on it's back side, which does line up with the frame damage. The photos hueyh posted has the binder on the clamp's front side. I wonder if this is a later design, maybe because of the issue the OP's version of frame/clamp developed? IMO binding on the larger radius of the ISP's front makes for a better design. Given this "new" info and different clamp I strongly suggest the OP contact Giant and 1- provide Giant with photos of his frame's condition and 2- try to discover if this "version 2" would fit and work on his frame.

Not mentioned is where along the ISP will the OP require the clamp to be for his seat height. If it was well below the "damaged" spot (and this would require a cutting down of the ISP, a process easily done and described in many other companies versions of this stupid design) then all this discussion is more moot then not. If the seat height requires the clamp to be positioned on the "damaged" spot of above it then this discussion is of potential great importance.

I do like Francis's suggestion of an internal plug of wood. Andy.

FBinNY 

Certainly, if the OP is going to shorten the mast, he'll be cutting his way out of any issue and that will end it. If he's shortening the frame by 2" or more, he needn't have posted at all.

As for the clamp. These are specific to the shape of the mast, and there may not be the option of mounting the newer design if Giant changed the tube shape. In any case, I don't think moving the bolt from back to front would make a difference, and the newer clamp assemblies appear to be shorter, so that might be counter-productive.

dimethi

The seat height I would like to set it to is pretty much what it's at right now-- maybe a couple mm down, but I don't see that making too significant of a difference.

I don't think I can swap clamps, and I think FBinNY is correct in that newer clamps are shorter.

dimethi

I re-did the coin tap a bunch of times-- it sounds SLIGHTLY duller when I go over the middle of the indentation. Does anybody know if that's significant? I want to believe that it's just because the clear coat is raised/changes the pitch...

A Calfee representative said the damage looked structural. Repair cost quoted $300-$350 with $100 for clear coat, and $150 for one color finish.

FBinNY 

The sad reality is that NOBODY can or will give you any assurances about this. It's easy and safe to say something is unsafe, but how do you say it's safe without buying into the potential consequences?

It's like when a pregnant woman asks about coffee, alcohol or whatever. For his own safety Doc. has to say "absolutely not!" Yet, to his/her own daughter the same person might say, "one drink now and then isn't going to hurt anything".

In the end it's your ass on the line, so it has to be your call. If you're not comfortable, have it repaired. OTOH if you make a decision to ride it as is (on your own, and not relying on advice here) consider buying yourself some added margin of safety, with an internal sleeve or plug to offer you a safety net if the mast fails.

Andrew R Stewart 

+1 on the above. BTW I was only suggesting that the OP find out if the new clamp fits and if so consider trying it in case Giant knows more then we do and that's why the different clamp is done the way it is. Andy.

dimethi

Update for anybody who is curious/may stumble upon this thread later: I sent it to Spyder Composites, and their xray showed 3 (very) small cracks. There was epoxy from the previous owner on the surface, which made the seat mast look a lot worse than it was.

Repairing and matching paint costed $180, compared to Calfee's quote of $300 repair + $100 to clear coat($300 to match paint). Communication with Calfee has been easier, since they reply promptly to emails; it is more difficult to reach Spyder Composite (calling/texting work best).

spdracr39

$180.00 to feel safe is a very worthwhile investment IMO.