Cracked bicycle frame...

Is it steel, titanium, aluminum,  or carbon fiber?

Just a minor correction...steel frames are not normally welded if they are the type with lugs at the joints.  Instead, they are brazed with either silver solder (newer) or brass (really old style).  There may be some welded steel frames out there, and if the joints are lugless, then they probably are TIG welded.  Aluminum frames are definitely welded.  A welded frame can be diagnosed and repaired, but it should be done by a competent frame builder, since he'll need to grind out the crack to eliminate a stress riser when the frame is repaired.  Normally a welded frame should not crack, since deposited weld metal has a higher tensile and yield strength than the base material itself.  A crack doesn't just happen, but usually appears as a result of some traumatic stress to the frame, such as a crash.  Titanium frames are welded, and even more care needs to be taken with them being repaired, since they should be welded in an inert gas atmosphere to prevent oxidation and contamination in the weld puddle.

Unless you are talking a very high-end or collectible bike, repair is never going to be cost effective.  Labor is going to cost more than the price of a newer, probably better, frame.  If it is under warranty, you'll get a new frame.  If not, start frame shopping and plan on moving your components over. 

I would be pretty carefull riding a cracked frame.  It is pretty much an injury waiting to happen. 

I would be leery of having this repaired unless it's by a qualified aluminum welder, and specifically someone who works or builds aluminum bike frames.  The tubing used in aluminum frames is thin and to an inexperienced hand, it's pathetically easy to strike an arc on a frame with a TIG torch and simply blow a huge hole in the tubing.  Now you've created even more problems.  You can also bring up problems with heat induced distortion any time you start welding, and it can be really easy to throw off the precise alignment in a bike frame, making it track poorly when ridden.

Like another post mentioned, unless it's a reasonably expensive bike, say like $3000 or more, it's not worth trying to fix the frame.  Better off to find a replacement frame and transfer all the components over.

I say these things about welding from nearly 30 years of experience as a nuclear and military certified welding inspector.  Granted, our company doesn't work on bike frames, but I do know what the hazards are with cracked welds, as well as the pitfalls that are there with trying to repair thin material.  Often times the damage to a bike frame is more than what might be visible to the untrained eye.  I use a variety of methods to examine welds every day, including magnetic particle (on carbon steel) and liquid penetrant methods, as well as x-ray and ultrasound.

Thanks for the update Dave!  It's been a long time since I've shopped for steel frames.  The last one I had was a custom frame built by Tom Kellog, who later started Spectrum Cycles and went into the titanium route too.  Yeah I agree with the Ti advice...gotta have an experienced welder and frame builder doing that one!

Mine's aluminum...so sounds like if it's a crack I should be able to talk the Missus into a new frame...jackpot.  Anyways, taking it in tomorrow to the LBS.  Fingers all crossed.

Oh, I bought it used.  So there's no warranty.  Anyway, thanks for the responses!

I got mine from him in 1977 when he was building them in his basement down the road from the Velodrome in Trexlertown PA.  He had just built all the frames for the 1976 US Olympic team and that kinda put him on the map!  Columbus tubing, instead of the old Reynolds 531 everyone else was using.  That was one of the stiffest frames I've ever ridden.  6 speed in the rear, an antique today!! 

I think at the time, he and Ralph Boston and Ben Serotta were all just starting up...it was a good time to be a custom frame builder in the northeast!