Smithie

Hey folks:

I'm in the process of fixing a 1982 Trek 613. As I try to de-seize the seatpost and stem (currently ammonia soaked), I noticed that the drive-side chainstay has some corrosion and is slightly indented at the location of the corrosion. So I have two questions:

1) Is that indentation completely due to corrosion, or did the 1982 613 have a mildly indented drive-side chain stay (the indentation is located where one would expect to see this, but it is very subtle, not like the very obvious pinched versions I am used to seeing)?

2) If this indentation is due only to corrosion, is the recommended repair to sand and clean to the bare metal, MAPP gas in some filler metal, and then sand it uniform?

Let me know your thoughts on this folks. Thanks!

Ex Pres 

Pictures would help.

But, I have an '83 600 with no chainstay indentation

JohnDThompson 

Agreed. Let's see some pictures before offering a remedy.

Smithie

Here's some images. Seeing it with the camera detail seems to make it pretty obvious that this is a straight corrosion issue. Any repair recommendations? I'm hoping to get away with a fully trustworthy repair using MAPP, but I am a rookie with the metal work so am open to other solutions. Thanks folks!

yuoil 

The stays look symmetrically shaped at least but that spot isn't intentional, I think. I would be inclined to suggest that it's damage from the chain or something that has allowed rust in. I would try to remove it without abrasion using vinegar or something and see how deep the corrosion is before I started cutting down with sandpaper.

Edit: I didn't feel I was clear with what I was trying to say about treatment. I was trying to say that maybe there is indentation and the corrosion is shallow enough that it can be removed and then you can seal the metal without having to do any repair work. To repair a hole there, if it's so deep, I'm not sure what would be best.

LesterOfPuppets

I would guess it's chainsuck damage. I'd probably just sand, prime and touch up personally.

Almost looks like a crack up by that blistered area in the first pic. Check that out closely.

Dave A 

Yep....looks like a dent from chain suck....which is likely what allowed the rust to form. Chances are its not structural...but, as has been mentioned, check for cracks...

Unless you are planning to repaint the frame, I would agree with Lester and probably just sand it, prime and touch it up...

Trek400

If you want to preserve the original paint, just use 3M Scotchbrite for rust surface, optional use bondo and light sanding to level surface, touchup paint. It's not visible spot anyway, it's behind the crank.

randyjawa 

My guess would be a bent crank ring or crank ring bolt that has been allowed to rub the chain stay. I see this sort of thing quite often.

The advice given so far is good. Attack the spot with, watching closely, as you clean it up. My guess is that you will find little or no issue to get too worried about. If, however, the area is significantly worn away, safety concerns might want to be taken into consideration.

Hope this is a help and this is just a guess.