ride lots be safe
Cold-setting head/seat tube alignment?
So I picked up a frame off ebay. Lugged steel Columbus, De Bernardi brand imported by Yellow Jersey in Madison WI. Riding it, I noticed it "pulls" to the left when no-hands. As in, when no-hands, the vertical axis of the bike tilts a few degrees to the left while going straight. So I have to cant my hips left a bit to keep the bike straight.
This makes it somewhat difficult to control hands free but is not noticeable with hands on the bars.
My first thought was, "cables pulling on the bars". So I unhooked all the cables except front brake (which obviously wouldn't cause any pulling) and rode again. Same pull, same tilt.
So I put it on my trainer. Not as accurate as a frame table of course, but reasonably straight. Now it's obvious, when riding the bike looking down, and especially when out of the saddle, that the head tube plane is a few degrees out of what vs the seat tube plane. Such that the front tire virtual contact patch is a good several centimeters left of the bike's centerline.
So. Is cold-setting a reasonable solution? Is it feasible for a careful home mechanic who knows his way around bikes? Methods? No idea how to set this up even if it's a good idea.... Alternatives?
Are you sure it's the Seat/Steer tube alignment and not an issue with misaligned fork blades or rear triangle? Those are more common as they can get tweaked in crashes, shipping etc. A front triangle misalignment on a new frame is more rare, as it had to have come out of the factory that way. It can be cold set, the bending would take some elbow grease if its enough out of alignment to see without a surface/alignment table. Seems like that's something Yellow Jersey should be able to take care of, I'd ask them first. A framebuilder with a table could do it easily and safely. If you really want to be brave and DIY, you could probably get creative with a solid bench vise, but you'd have to be really careful not to distort the tubing in the process, you'd want to make some tubing blocks (you can make these with a couple of blocks of wood, drill a hole in each the same diameter as your seat tube and then cut them in half, hold the tube in the vise with the blocks). Hold the seat tube in the vise between the blocks with the frame vertical, HT at the top, stick a 2x4 through your main triangle and tweak it. The problem is not having any precise way to measure the alignment except lining up the tubes by eye, but clearly you can make it better than it is if you can see that it's off. If you don't have a heavy bench vise, then you're on your own, go medieval with some scheme with long levers. Twisting the main triangle may also throw the alignment of your stays off, although those are more easily measured and fixed -see Sheldon Brown's string method... (Thanks Sheldon, RIP!) To see a front triangle alignment done right, here's a link to a youtube video of Paul Sadoff at Rock Lobster with a proper alignment table.
Last edited by ZenNMotion; 02-26-08 at 02:52 PM.
ride lots be safe
Thanks, that's about where I was at.
I should emphasize that I don't think Yellow Jersey or the builder is at fault here; this frame has clearly been used, it's several years old, I'm not the original owner etc.
Probably I'll take it down to Hans Schneider and have him look at it.
I corrected a head tube / seat tube misalignment on the cheap once. I secured the bb of the frame in a bench vice. I then inserted a weight lifting bar (with an aluminum tube over the end that was bigger than the bar but smaller than the head tube to act as a buffer) inside the head tube. Next I pulled with all my might. It took way more force then I imaggend but I was able to straigten it out.
Sounds most like a fork issue. Can you stick a different fork in a test ride it?