I'm considering converting an old frame I have from being a single-speed to an internal-gear bike. Problem is, though, that ALL internal gear hubs seem to be for 135mm dropout frames. What I have is an old Panasonic touring frame with Tange tubing (butted in the main triangle, straight tube on the stays if I am correct) which has previously been set to 126mm. Since the frame was a cast-off I collected when my trashy neighbors got evicted and all their stuff was put to the curb, I remember that the frame wasn't straight when I snatched it off the street and had my local mechanic cold-set it to 126mm (it may have already been a 126mm frame for all I know).

So, is it advisable to cold-set a 126mm frame to 135mm? What about a 120mm frame? Or, maybe I should be asking if anybody makes an internal gear hub in 126mm spacing?

First only relatively recent IGHs are 135 OLD. The classic OLD for Shimano and SA (and Sachs) for decades was 110 plus or minus.

Since frame failure from excessive cold setting is typically non catastrophic in failure mode I wouldn't be too worried about the safety aspect. But I would limit the investment just in case.

So how much is too much? How many times is too many times? Who knows, because the answer is really only known when the frame starts to crack, or doesn't. Andy.

In most cases, that plus or minus is a fairly significant number when dealing with Sturmey Archer hubs. I've mounted SA 5 speeds between dropouts ranging from 113mm to 135mm by adding, subtracting, re arranging spacers and nuts, and at the upper end, mounting the anti rotation washers inside facing out. Lots of flexibility there.

Older steel frames can usually just be sprung out 5-6mm on a side, in my experience. Just spring the drops in or out, center the wheel with the chain appropriately tight, and tighten down the axle. Double check that the wheel is still centered. Eventually, the frame will take the new set. I've done this for years, on many many bikes with no failures whatsoever. If you have to change a LOT (Like say, 3-4cm total.) you probably need to have the frame set, or, if it's an aluminum or CF frame, then you need to get a bike shop to do it, or play with the spacers, washers, etc. Steel is forgiving that way.

Be careful. On my first cold set, I thought I would have to press really hard using the Sheldon Brown version with the plank. Wow, that was a bit of overkill! I ended up manipulating each side by hand. Use a string line from the head tube back to the outside of the rear dropouts, and use a ruler to measure distance of each length of string away from the seat tube.

The thing I would watch out for after spreading, however, is ensuring the dropouts are readjusted/bent to ensure they are parallel both horizontally and vertically. There is a tool for doing this, but if you are clever enough, you can make up one with long bolts the diameter of the axle, and nuts and washers of suitable size. This also allows you to do the right amount of bending in the correct directions.

Some of the old drop-outs are quite thin steel, which makes that part easier. But newer dropouts can be quite thick, making it more difficult, And if the drive-side drop-out also incorporates the derailleur hanger, that will need to be checked. Another spot to check is chain-ring clearance on the drive-side chainstay; it shouldn't be an issue because it's so close to the BB, but nevertheless, it helps to check.