IF AND ONLY IF YOUR BIKE FORK IS MADE FROM STEEL then you can inexpensively align dropouts/ fork ends.
If your fork is made from anything else (aluminium, carbon fibre)
then this **won't work** and you could damage your fork.
Before we align the dropouts it's critical to make sure that the drop outs really are the problem.
Correct diagnosis of what's bent is the key to a successful repair.
Remove the wheel and take a step back from the bike and look at the fork in all directions - side, front, back. Use a yard/meter stick if judging alignment is problematic.
You want to make sure that it really is the drop out that's bent.
- Do the fork blades align with the head tube correctly?
- Do the fork blades align with each other? - it's possible one blade is bent and the other is straight.
- Is one or more blade twisted?
If you are sure the drop out is the problem Sheldon Brown has a page with good suggestions.
The beginning of the article has several warnings:
Note, if you're not careful, you can do serious damage to your frame this way!
If your frame is made of aluminum or carbon fiber, do not attempt to re-space the frame: these materials are not suitable for "cold setting."
If in doubt, try the magnet test: if a magnet won't stick to it, don't try to re-space it!
Toward the middle of the article the inexpensive options are described:
Fork End Alignment with Improvised Tools
Sheldon has a picture of a rear drop out and he's using an axle cut in half to judge alignment.
The same principle works with two large and long bolts with appropriate washers and nuts for fork ends. You may be able to get the bend you want by applying force to the appropriate axle/bolt.
Another method to bend drop outs is to use a very large adjustable wrench.
I've used both of these techniques individually and together with some success.
Sheldon ends his article with this summary:
This job isn't for everybody, but it's not rocket science either. Many shops are reluctant to undertake this sort of operation, either because of fear of liability or because they want to sell you new bike. Although it seems fairly alarming to deliberately bend your frame, it is really not that cataclysmic an operation, and can be very worthwhile if it allows you to keep riding an old friend, with the advantages of a modern drivetrain.