By how much can I safely cold set a steel frame ?

Icicle19

I have an old steel frame with a rear hub spacing (ie distance between the rear drop-outs) of 110mm. I'd like to upgrade the bike from hub gears to a more modern indexed derailleur system, with as many sprockets as I can fit in to the space available. So I'm wondering by how much I can reasonably attempt to cold set the frame to make more room.

Sheldon suggests cold setting is fine for at least a 10mm increase (ie 5mm each side), so I could likely go to 120mm, but that still doesn't give a lot of room. Going to about 126mm would be better - can anyone advise if this is feasible or not ? Or is this pushing my luck ? Thanks.

Garybee

110mm?, that is very narrow. Do you know how old/what type of frame it is?

When you flex a frame by this much it will often start to bend quite sharply at the brake bridge/seatstay junction.

HungryCol

Got for it.

Disclaimer - Frame may brake.

Icicle19

Garybee - it's a Hobbs of Barbican frame, and I reckon it dates from July 1947, or leastways thereabouts. 110mm was a common hub spacing back then, as many bikes came with only 3 or 4 hub gears (often courtesy of Sturmey Archer).

Garybee

Oh right, well i've learned something new today then. I thought that the earliest standard was 120mm. Although thinking about it logically i would expect it to coincide with a certain number of inches, which it doesn't appear to do.

rustychisel

Personally, I would not. 110mm was quite common and good for track wheels also. I'd not want to bodge (sorry, cold set) a steel frame out to 126 or 130mm, especially given new frames are really quite cheap.

Incidentally, for a frame of that age I'm certain you'll come up against other problems which may render the whole exercise an ENORMOUS PAIN IN THE ARSE. Such as, lack of braze-ons and cable stops; non standard bottom bracket or headset fittings; difficult to match seatpost diameter (you have checked the seatpost isn't frozen into the frame, haven't you?) and so on, and it was almost certainly bult for 27in wheels rather than 700c.

Monty Dog

IMO turn it into a nice retro-fixed or single speeder rather than risk trashing the frame. If that's not what you want, I'm sure somebody will swap you a frame more suited to your task. I'd hate to see a decent frame trashed for the sake of turning it into a half-baked bike.