Lugged MTB - headtube replacement
 

So unfortunately I have cracked the headtube on my beloved 1984 Trek 850. I'm of the understanding that this is something that can be repaired/replaced.

I'd like to know if anyone may be able to share what a frame repair like this might cost? (excluding paint).

Also, I'd like to know if anyone has any insight on what might have led to this failure, and if it would be something inevitable to happen again? Or as a friend suggested, is it just possible there was too much heat in the original brazing of the frame?

https://cimg9.ibsrv.net/gimg/bikefor...beadc78480.jpg

I'd guess $50-100 would be typical. It's one of the easier repairs. Cut as much away as you can and then grind the existing tube out of the lugs so that a new HT will slide in and then use silver to braze it in. They should then ream it to spec. It's probably an hour worth of work.

I'm curious now if any of the Trek mountain bikes had the one piece headtube/lug construction like some of the road frames. That does look like it started right at that joint, in the one piece headtubes that would not be a joint at all.

Edit: Seems maybe this is a cast one piece unit and the fake lug edge can cause a stress riser?

WTF. Try 3 x that number as a start. Doing all that work in under a hour is ridiculous, plus shop supplies much less some profit for the tradesmen who does the work.

I'd like to know how a head tube breaks like that. Any input from you pros?

Another user in the classic and vintage forum says that it is a one piece headtube. Is there an easy way to confirm? If this is true, could you explain how everything joins together instead?
Also I'm assuming that may make this way less feasible to repair?

not what you want to hear - but consider a search for a replacement frame

Oh no!
Have you been riding off road? I've been wondering if 531 is not the best choice for MTB. Love that bike and hope you can get it fixed reasonably.
Good luck.

it is easy to tell if it is a one piece head tube/lugs. If you look into (inside) the head tube and see big holes into the top and down tube then you know it is a one piece unit. If there are no holes, then it is a a standard head tube joined to a couple of lugs. These all-in-one units were made by Nikko in Japan. They are bulged formed. I used them when we made the 1st 50 sets of transportation frames in Bucha, Ukraine. Here is a picture of the lug unit and another picture of one of our transportation frames using one of those units.

https://cimg8.ibsrv.net/gimg/bikefor...a645df909.jpeg
https://cimg9.ibsrv.net/gimg/bikefor...23546178a.jpeg

I had already started seeking another as I wanted something built up close to original, and one built as pictured below with 700c!
Unfortunately, with this being such a short lived style of mountain bike in a very odd size, I'm not ruling out repair as a feasible option.

Absolutely have been riding this bike everywhere, and I have no regrets! Technically it's 531 all terrain so the tubing is pretty oversized, and the 531 isn't what failed! It's honestly one of the best steel frames that I've ever ridden. Way more responsive that it looks, but you wouldn't mistake it for stiff either.

https://cimg7.ibsrv.net/gimg/bikefor...760d4daeab.jpg


Thank you Doug, I really appreciate the visual, that is exactly what I have.

Measure the length of your head tube. I bet I have the exact head tube/lug replacement. It came from left over materials from Miele in Toronto when they went bust.

That would be incredible! I'm measuring 20cm!

Oops, the one piece head tube/lugs that I have were for Miele road frames and as a result have 1" top lug sockets and 1 1/8" down tube sockets. I just measured one of those and it is around 212mm long. I'm assuming your Trek has standard oversize tubes? is you steerer 1" or is it larger?

It isn't impossible to repair your frame by removing the lug unit (after cutting it into 2 pieces) and replacing them with real lugs. Of course this depends on the geometry of your frame. I also have a large assortment of odd lugs that might or might not work. Also it might be possible to braze an internal sleeve inside your broken head tube. That would probably require turning some stock thick tubing down on a lathe to fit the ID of the head tube and still leave room for the steerer. Of course all this work comes at a cost even before it is repainted. Yours is a pretty big MTB so there might not be many of those still around but if there is, the price is likely to be much less than a repair by a competent builder. Whether you want to explore getting yours repaired is going to be primarily based on its sentimental value to you. If you loved the frame/bike and want to make it like new again then whatever it costs is wroth it.

Top tube is 28.6mm down tube 31.8mm. The frame takes a 1" steerer.

I think a repair is still my most favorable option. There aren't many of these out there. I was looking for a second to leave built up closer to original already before I broke this one! Also, if I were to find another Trek the same as this one, it would have the same headtube that is prone to failure. If I were to replace this headtube with something stronger rather it be lugged or fillet brazed, I would have an improvement over the original design! I understand the repair will cost more than the value of the frame, but I have no plans to sell this frame down the road. It's been my most ridden frame since I picked it up this summer.

I have already reached out to a couple of framebuilders here in Georgia. One is no longer taking on repair work, and the other seems to discourage trying to repair the frame, so I'm not sure they really want to take on the work. They did say it would be in the range of $3-500. If I could stay closer to or under the $300 price point, I think it's a no brainer to try and get this back together.

Did they even bother to miter those tubes though? It would be a different bike after repair if they didn't. But the way that the lugs are so long onto the top and down tubes makes me believe they just cut them square.

I built a 531 frame back in the '70s and I like it more than I think I should. There is a lot better tubing available nowadays, but if some 531 fell into my hands for a decent price I would probably build another one. I don't see anything wrong with a 531 mountain bike. And of course, the 531 didn't break on the OP's bike anyway

click on duanedr's website he is a frame builder and he lists repair cost on his website as $100 for tube replacement so probably a good way to go. post number two website is in his signature

Yes, but not well I believe.
https://www.bikeforums.net/classic-v...k-600-a-3.html This thread goes into some detail about the headtube replacement on a Trek road frame.

Here's how mine look.
https://cimg0.ibsrv.net/gimg/bikefor...f585f8d5fc.jpg
https://cimg1.ibsrv.net/gimg/bikefor...0034bce493.jpg


I've had a few 853 road frames and love them, but this bike with 531 is just perfect. Of course, the 485mm chainstays may be deserving of the credit for the smooth ride.

doh! good call!

I see this as a challenging repair. The easiest thing to do would be to fillet braze it. The problem is that the miters are going to be off so without redoing the miters, that will weaken the joint. Because the tubes are already in the frame, that makes it difficult to hand miter each end somehow so a head tube will fit flush against both tubes and at the right angle. Of course just a little length will be lost but that won't matter. I'm doubtful there are some old lugs available somewhere that are close to the right angle. Very few lugs were ever used on mountain bikes. If you could discover the angle of the down tube to head tube, I could check my stash of old lugs. Every frame builder has his own methods of doing something and working to different standards. The way I would repair this Trek would not resemble the method used on the thread you posted about a head tube repair of a one piece head tube/lugs. Of course I am not in the running to repair yours because I don't have time with my teaching schedule.

Yes, those frames used a one-piece, bulge-formed head tube. I was there.

Yes, known issue, but seldom a problem before several decades of use.

The problem was not the 531 "All Terrain" tubing, but the one-piece head tube, which was not 531 tubing.

The steer tube is 1", but the down tube is 1-1/4" and the top tube is 1-1/8"

That is most feasible repair I see for this, or perhaps fillet brazing a new head tube.

Yes, the tubes were mitered.

If this were mine, there are two possible repairs I would make. The ugly option would be to fixture the head tube back into place, clean it up and TIG weld the head tube back together. The less ugly option would be to leave the lug portions that are on the top and down tubes and grind/file away everything else. Then clean up the miters and fillet braze to a new head tube.

I didn't consider that this might be one of the combined HT units, but the solution is the same. Grind the ID out to slide in a new standard headtube. I would leave the rings at top and bottom.

Well, I'm not sure I'm comfortable with that label. I have a small pro-hobby repair and frame building side gig. I have a few handfuls of repairs under my belt including top, seat and headtube replacements. I haven't seen nearly as much as Doug or many of the others here.


Doug seems to be outlining the approach I would take. Grind out the lugs to slide in a 32mm 1" headtube.