base2 

This may be more general cycling related, but since the bike is a tandem, I figured I'd post here as a friendly reminder to do a thorough inspection before taking your prized bikes out for a lovely spring time spin.
Below is my 1993 Trek T-50 tandem with the down tube cracked in not 1, but both water bottle bosses.

If something doesn't seem right, it probably isn't. Check it out.

20190319_163928 by Richard Mozzarella, on Flickr

Good luck all!
Aaron

lichtgrau

I'm feeling with you guys. A crack in the backbone...

Is there even a chance to heal that frame? Probably not. As it looks to me the bosses weakened the frame in a way that induced some crack starters. Probably due to a suboptimal welding process and therefore probably from the very beginning...
And since Trek is big and great bike company aware of the potential reputation damage of frame issues of that kind - I would at least inform them about the incident. In order to give them a fair chance to learn about that problem and -who knows- they probably even have a solution/compensation for you. I wouldn't like those pictures going around in the web if I were them... Good luck.

And since we're on a tandem tour right know - Thanks for the wakeup call to be attentive towards the gear we're using quite carefree sometimes. Just yesterday one of my newly installed cranks became loose and I was glad to realize it before something bad happened. I will check "the engine" more conscious and thoroughly this morning...

OneIsAllYouNeed

26 years is a decent run for a production frame. Out of curiosity, for most of the bike's life, (1) has it had flat bars (rather than drops) and (2) does the captain like to mash (rather than spin)? We had a 1997 Trek tandem that's still on the road.
If you love the bike enough, contact your local steel framebuilder about getting the downtube replaced.

base2 

For most of the bikes life it had flat bars. Then last year I did a drop bar conversion that turned into a complete overhaul with Shimano 105 shifters, 3x10, gears, Suguino 10 speed triple, bottom brackets, cables, brakes etc...New Velocity Chukker wheels, with a Phil & Son 28 hubs, & Arai drum. About a month ago I did a threadless conversion with a Wound-Up Tandem Duo fork & threadless headset (with 1.25 to 1.125 bushings) so that with the variety of stem choices, I could get the fit right.

I did finally get the fit right, (I think) So I was taking it out to do the bartape for a new season of riding.

My stoker & I both have Powertap P1 power meters, so the link below is 100% accurate of my (Captain) efforts. Add in another 103 watts of average power for my stoker on that ride (I am not allowed to get a link to it due to privacy settings) My wife also is of similar power when she stokes as well.

Average cadence is usually in the high 80's, bumping 90 most of the time.

Pretty indicative of a typical ride

LV2TNDM

To answer one reply about repair: yes, it's repairable. But most certainly not even worth the trouble. A steel downtube can be easily replaced. But it's expensive and entails repainting the frame (unless you can live with a rattle-can hack job just to prevent rust.). And repainting a tandem frame is pricey. But the REAL issue is future failures. A 1993 tandem with such a significant downtube failure is at the end of its lifespan. It's most certainly just a matter of time before the seat tube or a stay or a dropout fails. Now it's clear that the bottle boss braze on work contributed to the failure. The stress riser created there was the culprit. But nothing lasts forever, so it makes sense that it went here. And all the other stress risers in the frame are probably ready to "go" too. In fact, it would be interesting to have non-destructive testing done to the frame. I'd put money on finding more micro cracks or failures that are still unseen to the naked eye and under the paint. But that's an uneducated guess based merely on experience.

In other words, hang that frame on a wall as a display to all the miles you and your partner put on it - and broke it with all that effort! That's an accomplishment.

Gee, I better take a close look at my old Cannondale tandem...

But mainly, thanks again for your post. It may save a life - or TWO!

Paul J

Sorry to hear about this, you really put some love into this bike to get it right where you wanted it. I was thinking that Trek didn't build their tandems but rather outsources them. Does anyone know if that is true, and if so, who built these? I wonder if the builder might be in the Pacific Northwest and nearer your location for a reasonable repair. If you can't get it repaired your parts group would land nicely on a different frame. Maybe someone here in our little group has a frame tucked away in your size.

MikeAndJean

Tandem frames break if you ride them enough. However, a mid-tube break like that is surprising. We rode our third tandem over 100,000 miles, mostly in Northern California hills, before the rear dropout cracked.

Alcanbrad

Just some observations: The exposed metal of the crack in the first pictures seems fresh (i.e. no corrosion). Did you sand or scrap the paint away to expose this metal or did this damage just appear one day? Also there are ridges in the paint emanating radially around the down tube from each bottle bracket screw. This is strange. Has the frame been repainted?

Perhaps when the bottle cage Pem nuts were welded in place, any anti corrosion coating on the inside of the tube was compromised and the metal corroded from the inside out, but again, I would expect to see corrosion on the exposed metal.

Have you inspected the insides of the tubes from the head and seat tubes and bottom brackets? If you see a lot of rust it may be indicative of thinning metal through out the frame making an attempt at repair not worthwhile.

base2 

I picked the paint away with a flat blade screwdriver, then hit it with a bit of sandpaper to get a clear picture of what I was dealing with. The crack goes all the way around the tube and the paint is buckled, (for lack of a better word) along the crack. The metal at the crack is very clearly aged & gray. There is no rust as this bike is stored in a climate controlled & dehumidified building. It's just fatigue from getting too hot when they brazed in the water bottle bosses. The water bottle boss is the only part that wasn't all the way through, but the crack can be seen creeping around the braze.

Last year it would sometimes get an enexpected "wobble" when under high speed cornering and it would do a "whip-whip" motion if also applying the brakes hard or standing on the pedals that it didn't used to. Basically anything that would subject the frame to severe twisting forces. I always chalked it up to something my stoker did. I guess now I should have been suspicious.

I'm actually thankful for the stiffener tube tandem builders tend to omit these days. That's what was actually holding the bike together.

The bike is now dis-assembled. All the parts saved to ride again another day. The frame...well, I dunno. Maybe I'll take a hacksaw to it to satisfy my curiosity & to prevent the possibility of someone thinking they rescued something destined for the recycler.

There didn't seem to be any rust inside, so I really think it's just fatigue. I wish I was the original owner. Trek warrenties their frames for life.

To the other post: It is very clearly made in the USA by Trek, but I don't know, if this was a contract built frame or not. It's an early one, so I'm tempted to think it was made in Wisconsin next the the engineers that designed it. But I could be wrong.

CliffordK

Where are you in the PNW?

While a replacement tube is likely the best way to repair the frame, I wonder if you could cut an 8" or so split tube, the next size up and braze on top of the bad section. It would be a very easy repair.

A little late now, but I wonder if these would have saved your frame.
https://www.cycle-frames.com/bicycle...NFORCMENT.html

averybikes

thanks for this important reminder

pickettt

What kind of bottles are you using?

dwmckee

I have seen another Trek frame splt like this all of the way around. It was caused at the stress riser of an internally butted frame, right at the butting... I am not sure if Trek offers lifetime warrany to the original owner, but certainly take it to Trek. Many times they will sell you a replacement frame at or below cost just to keep the brand image up. They do not like seeing pictures of their bikes like this in chat rooms.

Several "good" brands have started to roll back frame warranties over the past two decades from the previous lifetime standard. Salsa for example is now just 5 years.