The other day, I realized that my mountain bike (cheap Raleigh Canada 2000) came with a 135 mm wheel crammed into 130mm dropouts - which explains why wheel mounting was always a wrestiling match.

I read Sheldon on coldsetting, and the lumber-through-the frame, bend-one-side-then-the-other method seemed dodgy. I came up with something much simpler, which loads the sides against each other to ensure symmetry. Tried it this morning, and so far as I can tell it worked great.

I should mention that I actually am a physicist (MIT 77), and also the inventor of a sometime-world-record pogo stick (the Flybar - 8.5 foot bounce, powered by a pound of rubber), so my confidence in some pretty commonsensical premises does have an explanation other than sheer arrogance.

The method is: remove the rear wheel, and put an axle in the dropouts - with nuts on both sides, inside the dropouts. Move one of the nuts outward to load the frame. Back off and check the effect from time to time; continue until desired spreading is achieved.

(I put a couple of washers outside the nut I moved, with oil, to minimize friction.)

I didn't know how far I would have to go to exceed the elastic limit and get permanent spreading; turns out that was at about 150mm. To get a 135mm set, I had to go to 159mm. It was very easy - no large forces involved, gently winding the wrench.

The beauty of this is that Hooke's Law (which is simply that strain varies as stress, and is approximately true for most things), and the physical symmetry of the stays, ensures that both sides will flex evenly, and therefore overload and set evenly - much better than eyeballing it and checking. As for dropout alignment and so forth - bear in mind that the bike has always operated with a 135mm axle, and still does. The shape hasn't changed - just the internal stresses.