Chain Drop Scratches

Discuss light weight issues concerning road bikes & parts.
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CerveloBert
Posts: 284
Joined: Tue Dec 20, 2011 12:43 am
Location: Los Angeles, CA

by CerveloBert

This is the first time my chain has dropped so dramatically. On top of that - I managed to finish two revolutions before realizing my chain was dropped to finish off some nice scratches. I went ahead and ordered a chain guard today to stop this from happening, but now I'm looking to self-repair the finish and paint where it was messed up. The integrity of the frame is fine - but the paint in the area of the chain drop makes for a morbid horror story.

You guys typically sand - repaint - then re-lacquer? I'm a n00b to this kinda stuff, so specifics would be nice. Would you recommend a specific paint and/or lacquer? A certain grit on the sand? I'm more interested in procedure than anything else.

em3
Posts: 887
Joined: Tue Dec 23, 2008 2:57 pm
Location: NYC

by em3

If you are dropping your chain so often then it is a clear sign that your frt mech is out of adjustment…a chain catcher is not a remedy for a poorly adjusted frt mech, but simply there for emergencies. EM3
Last edited by Powerful Pete on Tue Mar 06, 2012 2:03 am, edited 1 time in total.
Reason: Deleted quote. PP
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by Weenie


CerveloBert
Posts: 284
Joined: Tue Dec 20, 2011 12:43 am
Location: Los Angeles, CA

by CerveloBert

Hey em3 - Thanks for answering my question... really.

If you need to know - the chain dropped on a brick road. This was the first time my chain has ever dropped, and it happened on a very bumpy and nasty surface. I guess if my derailleur was set correctly though - it shouldn't matter if I was biking on the surface of the planet Mars right?

SL58
Posts: 642
Joined: Tue Oct 30, 2007 5:02 pm

by SL58

I wouldn't refinish anything - it is hard to do a good job if you are not a pro.
I usually take a thin Alu. sheet and cut a nice teardrop patch from it, roll it
to get it to fit chainstay and glue it on. It will protect your frame and it can
be replaced if need be. I do use chaincatcher just in case.

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theremery
Posts: 2673
Joined: Sun Jun 12, 2005 10:56 am
Location: New Zealand

by theremery

Post a pic and we may be able to suggest if you are likely to make the finish WORSE when trying to fix it. Alternatively, Lizard skins makes a faux carbon protector that may well completely hide the offending area AND protect it AND look good :)
Updated: Racing again! Thought this was unlikely! Eventually, I may even have a decent race!
Edit: 2015: darn near won the best South Island series (got second in age
-group)..woo hoo Racy Theremery is back!!

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Getter
Posts: 877
Joined: Sat Nov 14, 2009 6:30 am
Location: So Cal

by Getter

^^That would be my vote. Trying to fix the scratches could make it worse. Something similar happened to my S2 recently. :noidea:

Ozrider
Posts: 1021
Joined: Sat Nov 20, 2010 6:06 am
Location: Perth, Western Australia

by Ozrider

I use "helicopter rotor tape" on my chain stays. It is a thick clear tape and once cut and stuck on is nearly invisible. It does a fantastic job. I also use a chain catcher as added security.
If you do an Internet search there are a few companies that do really good touch ups, or if not too bad just cover with a stick on chain stay protector. It always sucks to have damage on your bike, but sometimes can t be avoided
Ozrider - Western Australia
Parlee Z5 XL (6055g/13.32lbs) Trek Madone 5.9 (7052-7500g)Jonesman Columbus Spirit (8680g)
Chase your dreams - it's only impossible until it's done

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Genshammer
Posts: 8
Joined: Thu Dec 15, 2011 7:14 pm
Location: Escondido, CA
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by Genshammer

As others have mentioned, I think the easiest and cheapest solution is to just use a chainstay protector that covers the blemished area. We can easily do the cosmetic work, but you're looking at a minimum of $75. Besides, the blemish is in an area that's very hard to see and can easily get damaged again.

If you want to take on the repair yourself, the procedure would be to use 150 grit to remove the chipping/flaking area so that it has a perfectly smooth, beveled transition to the non-damaged area around it. Feel out with your finger. If you can feel a lip from the sanded area to the undamaged area, it will show up in the finish. It's got to be smooth. Once you get it smooth, then use 320 grit to sand out the 150 grit scratches. Then use an automotive grade clearcoat to finish. I would recommend airbrushing, but if you're careful you can probably rattlecan it. Let the repaired area cure. If you can heat it up to 130 degrees, it will cure in about 5 hours. At a temperature of 70 degrees, it will probably take a day. Either way, let it sit overnight. If there are any runs, wet sand them out with 600 grit, then use a polishing wheel and a good quality polish to shine it up.

Like I said...just put a chainstay protector on it and save yourself a bunch of time and money! :wink:
Kurt Gensheimer
CarbonFrameRepair.com
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CerveloBert
Posts: 284
Joined: Tue Dec 20, 2011 12:43 am
Location: Los Angeles, CA

by CerveloBert

Thanks for the tips. I think I'm going to reconsider the finishing job per recommendations from you guys. I'll go ahead and get that protector and maybe put the re-finish job off for a cold and lonely offseason. Thanks everybody.

by Weenie


Steve_W
Posts: 296
Joined: Sun Oct 19, 2008 12:40 pm
Location: England

by Steve_W

I loved the first response....ask a simple question.
Back to the task in hand....
I tried patching some damage up, and like yourself a noob in this field of work, I made a complete arse of it, being a perfectionist its wasn't to be.
So I took it off to a car bodywork repair shop....did the job perfectly, a lot cheaper then I expected, £30.
Steve

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