Bicycle Mechanics - Paint touch up..sanding cf frame?
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10-25-08, 11:04 PM
Hi all. I have a small but noticeable paint chip on a carbon fiber frame, and the chip goes all the way to the dark CF. No damage I'm told, just cosmetic. I have paint that I guess is a close enough match, but here is my question:
I built up the layers of paint slowly, but now that area has a slight bump, and in the light appears dull compared to the rest of the bike. Is there a sand paper with fine enough grit to level out the surface without getting into the unaffected areas? Should I wet sand? And finally, is the touch-up paint (metallic) dull because I didn't use clearcoat? Any advice is welcome. If it matters, the factory paintjob was from Cervelo. Thanks for any help!
10-25-08, 11:13 PM
Mettalics are incredably hard to match unless the touch up paint came from the original batch. So it's likely you're stuck with a slight mismatch.
But as far as blending it down fairly well you can do this. Mask off the area so there's the patch plus about 1/16 inch of original paint all around. Depending on how much of a bump there is you may want to start with 1000 or even 600 grit to level it. Once level and you notice you're starting to cut into the surrounding clear coat switch to 2000 and smoothen out the spot. Then switch to a small pad of paper towel using automotive rubbing compound to further smoothen and bring up the luster. Then go for the white automotive polishing compound to bring it up to almost a shine. Finally finish it with a good "self cleaning" auto wax. That'll both finish the polishing job as well as waxing the spot.
THe tap should be left in place for all the wet sanding and the rubbing compound portions. Then remove it for the polishing compound and waxing steps. Because the water during the wet sanding covers your work you will need to dry it for inspection often. That's just part of the job when doing something fussy like this.
The treatment above worked for repairing a small nick on the wife's new motorcycle some years back. So you KNOW it worked under stress and since I'm still alive to type this that it was successful.... :D
10-26-08, 12:26 AM
I'm looking forward to trying this. You are right about the difficulty in matching metallics, and tech support at Cervelo says they don't sell touch-up or have a spec on it. I suspect the bikes are painted overseas, so that makes sense. Still, if I can get it smooth enough to blend with the rest of the surface I'll be a real happy camper.
In any case, thanks so much for such a thorough and helpful reply! That sounds really straight forward, I can't believe I never thought about tape! Does it really matter what kind? electrical, scotch, etc?
10-26-08, 07:13 PM
Or is there some special type of painters tape that people use for auto detailing, something that won't harm the finish and is pretty thin?
Find green masking tape. It works just like normal masking tape, but leaves no residue when removed. It's good stuff.
10-27-08, 09:13 PM
10-27-08, 09:18 PM
Green would be best if you need to buy it anyway. But any masking tape is fine if you have some already. It won't be on the frame for long in any event. It's just there so that you don't rub the sandpaper on more than the spot and the immediate 1/32 inch or so around the spot.
10-28-08, 08:07 PM
Thanks again for the advice. I forgot to ask this earlier, but you said to sand until I hit the clear coat. Is there a sure way to tell when that happens? Does the clearcoat "scratch" or discolor in some way, or do I just look for a change in thicknesses?
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