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-   -   '82 Trek 710 Frame Repair (http://www.bikeforums.net/framebuilders/573962-82-trek-710-frame-repair.html)

bernside 08-14-09 05:41 AM

'82 Trek 710 Frame Repair
 
Greetings. I hope this is the right forum for this post - I am looking for educated opinions...

I was changing the rear wheel on my older Trek when "pop" the cross tube that holds the rear brake pulled free from one of the seat stays. Looking at the joint is it rusted except for one tiny 1/8" spot so this has been just waiting to let go for a while.

Several years ago the rear end was damaged and the seat stay had to be bent back into shape. I assume this put pressure on this joint or cracked the weld then and it has just now given up.

My question is - how should this best be repaired and what would a reasonable cost be? Can a competent welder do it or do I need to find someone who knows bicycle frames?

Can the two parts be pulled together and welded or will this result in stress on the frame because they are being pulled in - in other words does the seat stay need to be rebent/reshaped?

I do not know of any frame builders in my area (eastern NC - anyone out there?) but will ask at the local bike shop this weekend.

I am a bit desperate because I have been riding 100+ miles a week and this is my only road bike. In fact I think I am going into withdrawal already.

Thanks for the advice,

-cgb
http://i130.photobucket.com/albums/p...0/DSC_0108.jpg

http://i130.photobucket.com/albums/p...0/DSC_0110.jpg

unterhausen 08-14-09 03:21 PM

I wouldn't have a welder do it. Almost anyone that has built a few frames is ok for this, I would stay away from welders that don't know bikes.

Paint is the biggest issue. I would think that you can find a framebuilder willing to fix this for $50-100 ready to paint. Not too many framebuilders will try to match your paint and do a spot paint job. Bilenky in Philly will do that.

I used to fix things like this for $5 when I was an undergrad. Too bad for you I graduated in '82. I fixed a lot of French brake bridges, they apparently had the really drunk guys braze all the brake bridges.

There is a significant amount of stress built into that frame. It's really hard for me to judge what's going on without having my hands on the bike. Just pushing it back into place would probably work fine, but it would probably be best to remove the other side, align and re-braze. My thought is that this frame isn't worth doing that.

Six jours 08-14-09 10:14 PM

I agree with everything Unterhausen wrote. If you can find anyone with any experience at all, it's a very simple project.

And this is actually a project you can almost certainly handle yourself. You'll need a Bernz-O-Matic MAPP torch which will run about $35, a one ounce coil of silver ($25 from Henry James), and a jar of paste flux, $11 from the some place.

Remove the paint for several inches around the area, and sand all the surfaces to bare steel -- no traces of rust, paint, or anything else. Paint everything with the paste flux, use something to clamp the surfaces together, heat them evenly to the point they just barely glow in a poorly lit room, and then feed in some silver wire. At the right temperature the wire will flow into the joint. Add enough that you get it built up all around the joint. For your first time, you'll probably make a bit of a mess and dribble some silver down the stay, but this is easy to get rid of with a file.

Let the joint cool down, then soak it in hot water for half an hour or so, to remove the flux. Dry it, do whatever level of cleanup you want with sandpaper and a file, and then zap it with Rustoleum, and you'll be back in business.

JohnDThompson 08-15-09 09:01 AM

Did you perchance spread the frame to use a wider rear hub? 1982 would have been right at the cusp of Trek's change-over from 120mm spacing to 126mm spacing.

If you plan on using a wider (130mm+) hub at some point, now might be the time to have a longer brake bridge installed to accommodate the wider spacing without undue stress on the rear triangle.

bernside 08-15-09 02:55 PM

Thanks for the advice guys.

I tried the bike shop and did not know of any local framebuilders or welders they would recommend for the job.

I already have the torch, the mapp gas and the flux so I figured I would give it a shot but could not find any silver in town so it will have to wait till the welding supply place opens on Monday, then I will have a go at it.

I will post up the results for your amusement if nothing else.

Thanks

-cgb

Road Fan 08-15-09 03:07 PM

Quote:

Originally Posted by bernside (Post 9492525)
Thanks for the advice guys.

I tried the bike shop and did not know of any local framebuilders or welders they would recommend for the job.

I already have the torch, the mapp gas and the flux so I figured I would give it a shot but could not find any silver in town so it will have to wait till the welding supply place opens on Monday, then I will have a go at it.

I will post up the results for your amusement if nothing else.

Thanks

-cgb

In or near Raleigh, North Carolina there's a framebuilder making the Coho frames, who does excellent work. If you can find him, there'a an in-state person.

Also in Greensboro, NC there's Cycle d'Oro http://www.cyclesdeoro.com/. This shop is one of the leaders of the recent vintage bike resurgence. The owner started up the Classic Rendezvous site, and has deep history in all levels of bike repair, including frames. If Dale tells you there's nothing in NC, then there's nothing, but I'd certainly look him up and ask him.

Lest you worry about "is my frame vintage enough," the answer is yes, and he might talk to you longer if you tell him that you were referred by a CR list member.

cudak888 08-18-09 11:15 AM

Aha, aha - another Trek frame that bites the dust because of a poor brake bridge.

Don't go to a cheap welder, or this will be the result (1982 Trek 720). This is after being shoddily filed:
http://www.jaysmarine.com/trek728_BDC_3.jpg

Don't cry if you're a C&V'er - this frame wasn't worth any better effort, IMO - and it rode like a sponge thanks to those outrageously long 531 chainstays.

-Kurt

bernside 08-19-09 07:19 PM

well...good news, bad news
 
The good news is that I found a place in town that sells the brazing silver on Monday and managed to do a half way decent job repairing the frame. Shot it with a quickie paint job and put it all back together so I could make the group ride tuesday evening.

The bad news is now the chain is jumping on the rear cassette every time I pedal hard in the smaller cogs. I replaced the chain, swapped rear cassettes, adjusted the (friction shift) cables, but nothing works.

I cannot figure how I changed anything with the frame that would cause this but I don't know...anyone have a clue....

http://i130.photobucket.com/albums/p...kintoshape.jpg
blocked the drops and massaged it back into shape with a rubber mallet

http://i130.photobucket.com/albums/p...dmorepaint.jpg
oops should have sanded more paint off

http://i130.photobucket.com/albums/p...10/painted.jpg
quickie paint job until I get another bike and can repaint this whole frame

-cgb

JohnDThompson 08-19-09 08:59 PM

Quote:

Originally Posted by bernside (Post 9521346)
The bad news is now the chain is jumping on the rear cassette every time I pedal hard in the smaller cogs. I replaced the chain, swapped rear cassettes, adjusted the (friction shift) cables, but nothing works.

I cannot figure how I changed anything with the frame that would cause this but I don't know...anyone have a clue...

Brazing the brake bridge will pull the dropout inward, toward the centerline of the frame. Did you check to see if the rear triangle is still centered with the main frame tubes?

cycle_maven 08-20-09 08:16 AM

Have you checked your derailleur hanger for straight? A crooked derailleur could cause the chain to be skippy. It looks like you needed to bend some things to get the brake bridge closer to the seat stay, and maybe the der hanger got tweeked in the process.

Ronsonic 08-20-09 10:55 AM

During this ordeal, was the bike partially disassembled and allowed to rest on the rear der. Damages them sometimes.

bernside 08-20-09 05:27 PM

spent 2 hrs at the bike shop test riding between changes. Frame is straight, derailleur is ok, changed out the chain rings and the cassette and its better, but still not quite right.

I am thinking about replacing the shift cable and possible the derailleur even though it seems ok.

The old chain rings and cassette didn't look too bad even to the guys in the shop...I have only been riding a year so I still don't know what looks right and what is wrong.

Thanks everyone for the help.

cudak888 08-22-09 09:48 AM

Quote:

Originally Posted by bernside (Post 9527583)
spent 2 hrs at the bike shop test riding between changes. Frame is straight, derailleur is ok, changed out the chain rings and the cassette and its better, but still not quite right.

I am thinking about replacing the shift cable and possible the derailleur even though it seems ok.

Hold on here. No need to replace the chainrings.

You didn't list replacing the chain, so I assume that you didn't - in which case, replace it. A used chain running with an equally uneven freewheel (or cassette, as you indicate; I assume you therefore swapped the rear hub at one point or another) will almost always skip. A new freewheel/cassette with the old chain will cause similar problems, as the wear remains uneven.

Put a new chain on with the new freewheel/cassette. Should work.

-Kurt

bernside 08-22-09 01:34 PM

Thanks Kurt,

I guess I left that part of the ordeal out...new chain was the first try. Then the thought was that new chain / old sprockets combo might be the problem so we swapped those.

The bike shop guys are scratching their heads. There are not a lot of things left to check....

cudak888 08-23-09 10:12 PM

Quote:

Originally Posted by bernside (Post 9537751)
I guess I left that part of the ordeal out...new chain was the first try.

So it's skipping with a new chain and freewheel? What's the freewheel/chain combo? For that matter, what is your RD, out of curiosity? Duopar?

-Kurt


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