I have a lynskey viable, which uses straight, round chainstays. I’ve crimped plenty of steel chainstays on built frames, but never on ti. It’s 3/2.5. Anybody have any suggestions? Ultimately looking to increase tire clearance.
I did see that Dave at Ti cycles has cut a notch out and welded a curved plate over it. I’ve welded stainless, but never ti, how different is it?
It’s famously difficult to make good long-lasting frames from Ti. Maybe if you’re a “natural” or the world’s greatest welder, then you’ll have no problem. I’d feel better about it if you got say 20 hours of practice on scraps before trying to weld a frame for someone to ride. Even that won’t be enough for most people, without instruction from someone who knows (1) how to weld Ti and (2) how to teach others to do it. Learning on your own without instruction is practically impossible.
My info is somewhat old, so take this with a grain od salt. Back in the '90s, all 3/2.5 Ti tube was made as aircraft hydraulic tubing. Even though the bike biz is now using enough that tubes are made from the start to be bike tubes, I believe they are still made the same way, by pilgering. This orients the grain in a way optimized for bending, so the tube wall doesn’t get thinner on the outside of the bend, which would cause a blow-out in high-pressure hydraulic systems.
But a tube made that way will probably crack if you try to indent it.
Originally when all Ti bikes were made with aircraft tubing, it was all delivered as CWSR (cold-worked, stress-relieved). This gains significant strength from the cold-working, but it’s bad for chainstays that need to be manipulated, like tapering, ovalizing, indenting, S-bends etc. So at least some (maybe most) Ti builder switched to annealed Ti for the chainstays. Significantly weaker than CWSR, but less likely to crack or split from shaping. If your frame has annealed stays, then you’re more likely to have success, but you mentioned straight round untapered stays, which to me indicates it’s an older frame, probably CWSR. So proceed with caution.
The Ti Cycles “potato chip” repair has a lot of history of success, so though it’s expensive, it’s the only way I would trust to get you the clearance you want, without cracking.
5 Likes
Mark,
Thank you for your thorough explanation. I am an an adequate welder on alloy steel, but by no means an expert who could translate skills to another material like ti, given your insights. The background of the material properties is enough to convince me to not put it in a vice. I suppose I’ll just run narrower tires for now.
Much appreciated,
Gef