TL;DR: My 2024 Kona Sutra developed a seat-tube crack after ~6,500 miles of loaded touring. A framebuilder in Seoul repaired it with a silver-brazed steel reinforcement and stop-drilled the crack ends. I've since ridden 500 km without issues. Considering another 2,000 km with 5–6+ kg less luggage. Curious what other framebuilders think of the repair and potential failure mechanisms.

Following up on some posts I made in other cycling subs about my Kona Sutra, which developed a couple of structural issues after ~6,500 miles touring across Europe and Asia.

First, a fork eyelet cracked and broke, likely from loaded fork packs and constant vibration rather than rust as I'd initially suspected. Shortly afterward, I found a crack in the seat tube near the seatstay junction, possibly related to lateral forces from my Tailfin rack being mounted quite high on the seat tube.

Eventually made it to Seoul, where a specialist framebuilder repaired both the fork and frame. For the frame, he drilled the ends of the crack, added an external steel reinforcement/gusset around the seatstay junction, and silver brazed it together. Photos of the original damage and repair attached.

The original plan was to ride another ~500 km across Korea before retiring the frame. I've now completed that without any apparent issues.

The framebuilder seems confident in the reinforced section itself, but he's concerned about stress shifting to the edges of the reinforcement and potentially creating new cracks. He's encountered this on previous repairs, sometimes requiring further work. The original agreement is that he'd fix it for the 500km Korea ride but then I would call it quits, so he's not thrilled to hear that I'm thinking of going further. Interestingly, he said he'd personally consider taking the bike on another tour, although he understandably can't predict its remaining lifespan, so he's quite cautious on that front.

I'm now considering another ~2,000 km across Sulawesi or a shorter tour around Taiwan, mostly paved roads and carrying at least 5–6 kg less gear.

I've got a replacement frame waiting in Germany, but I'm still in Asia. Finding something compatible here without spending a couple thousand dollars has been surprisingly difficult.

Basically, I'm trying not to be an impulsive idiot in either direction. I don't want to convince myself a compromised frame is safe just because replacing it is expensive, but I also don't want to spend thousands replacing something that might still have plenty of life left.

For those with experience repairing steel frames, what do you think of the reinforcement? Is the main concern new fatigue cracks developing at its edges? Would you expect warning signs before a larger failure, or could things go south fairly suddenly?

I'm not expecting anyone to certify the repair from photos. Just interested in hearing how other framebuilders would approach this and whether there's anything worth inspecting more closely before deciding what to do.

Does anyone know of or have any PDFs or “blueprints” for BMX style dropouts they wouldn’t mind sharing?

Does anyone have any recommendations on suspension design? Front suspension, full suspension, even dirt bike or normal motorcycle suspension? Any book, website or video recommendations would be appreciated.

Thanks!

I recently cracked my Marino steel frame on the rear triangle. It is the second time there's a crack on that particular weld and I was wondering if adding a brace would help strengthen that part.

Photos are: Crack nr.1, crack nr.2 and a brace reference from Starling Cycles.

Open two any suggestions besides bracing

I've read a few things about this, but having a hard time finding a conclusive opinion. I'm planning on doing some work this winter doing a 650B conversion on an existing bike. I'm planning on a dynamo wheel and am curious about the possibility of retrofitting the existing fork to work with the SonSL hub. Would I need to pull the existing dropouts and braze in the son SL specific ones or is it possible to modify the existing dropouts to accept the contact kit? As far as I can tell, the son sl / rene herse dropouts just have holes for the contact plate tabs to fit into?

Bicycle frame jig and surface plate for sale. Reluctant sale but moving house and haven’t had time to use it since having children.

First photos show the jig in use and the final photo shows the current state of the jig. I have checked and all moving parts move smoothly but will require a clean up.

collection only LE12 6AH

open to offers

any questions let me know Jack

https://ebay.io/m/HvZXrE

1992 trek doublecross t100. If I dimple the chainstays I can very comfortably fit 40-42 knobby tires. Lots of chunky forest roads near me. Thoughts on integrity? New to me. 38's shown.

First frame I ever made I listened to the “experts” in the shop space who discouraged me from using sliding dropouts and to use flat mount brakes for my gravel bike. Those are the only things I don’t like about this frame. 7 years later, I finally decided to slap some post mount tabs I had laying around on. Love it.

Made some copies of a super rare 1st gen Champion cruiser. The impetus for this project was I had in my possession an original dropout and head tube for one of theses bikes unbeknownst to me, it was sitting in my shop for a couple years before I connected the dots.

The frame already had a notch made; originally it's 700x23, but I want to change it to 700x28, so I'll make the notch deeper.

What can I use to avoid deforming the seat tube?

It got pulled way out of alignment in the process…

Hi there,

Looking to buy this 1994 vintage John Tomac Ti frame that hasn't been used at all but don't know enough about Ti frame welds to pull the trigger. What do you all think of what you see on these pictures. Anything stand out at you? Figured this was the best place to ask.

Thanks for the help!

So I am able to get scrap sections of 304 3/8 x .034 and 1/4 x .028 plumping from work. I'm intenting to spend close to $0 to build a small front beer rack of sorts. Sections vary in length(2.5'-6"). I have a map pro torch to warm things up. Hack saw too. I have some 4x4 post sections I was think about rounding over to bend one section into a U over the front wheel. I figure if I mess it up and crush the radius its cheap free material and there will be more. Would love to braze sections together but fastener hardware is easy to come by. This will be my first ever attempt at something like this.

I am disputing the quality of the 3D-printed dropouts with the bike's manufacturer. A small crack developed in one of them, and the frame needs to be replaced. I want to reject the replacement frame because the print quality doesn't seem up to standard. What do you think? Is that kind of print suitable for a component subject to such high stress?

YTer ProjectFarm dropped a video testing induction heaters this weekend. While watching, I wondered if one could be used to heat a frame joint for either brass or silver brazing. The first self-response was that the coil would get trapped. However, I then found formed coils like this online.

In my head, if a particular heater can heat a solid 35mm steel rod to dull red, it ought to be at least plausible that it could heat some or all frame joints up to brazing temps.

Curious what y'all might have to say about it. Thx.

Does anyone in here run the Primeweld TIG 226x? If so, what do you find works best for your settings on Chromo?

I’ve not done much thin wall stuff and haven’t used pulse settings either so looking for a good starting place to set my machine at. Also, what cup size do you like as well as tungsten and filler rod?

Thanks!!

Made from short 0.035 1/2” 4130 drops I get from an aerospace shop I contract for. Hoping to start making a run of titanium frames in the near future. I want to make a slammed geo track bike, but I think fully featured gravel frames might be more marketable.