Do you know Doug Fattic ? He's in Niles Michigan and has more fork alignment knowledge in his little finger than... OK enough with the labored cliché, let's just say he's very good. Not sure if he takes in repairs. He does teach framebuilding classes though, so take one and then you'll be able to align your own forks. Or at least he'll be able to point you to someone who does fork alignment, maybe one of his students. Maybe he'll chime in on this thread now that I've mentioned him.

Mark B

Free time in retirement is a myth. Ask a retired person.

I think my colleague Matt Assenmacher recently retired. He went to learn in England a couple of years before I went over. He was located in Swartz Creek (near Flint). Anyway since my wife retired (and I didn't) my time in the shop has been mostly limited to teaching frame building classes and having any time to make frames or do paint jobs for customers. However doing one fork alignment can be squeezed in somewhere.

What Mark said. Doing a decent fork alignment requires some specialized tools. Most frame builders check fork alignment in their fork making fixture. Fork alignment starts by getting the dropouts equidistant from the fork's steerer or centerline. This is where a special tool is needed. Once the left/right equal distance is accomplished, the next step is to get the fore/aft right. Not only does the ends of the dropout slots need to be the same distance long, they also have to have the same amount of original rake (unless it is purposely being changed). Sometimes some research has to be done to get that right. What can happen is that the bike can have a front end accident and that can bend back the blades. There is nothing on the fork itself to tell you what the original rake should be. I have tooling to easily measure rake on a fork. Once that has been done, then the H tools can be used to square the faces of the dropouts so they are parallel with each other. And now finally a true wheel can be used to see if there are any discrepancies. It should center. If the fork has a 1" steerer, it is easy to look down the steerer to see if the rim leans to one side or the other. I'm not opposed to filing the dropout slot a little. I do this by laying the file with about the same radius as the slot width in both dropouts and use the opposite dropout as a filing guide. I just put pressure in the one needing to be filed. Of course like any alignment, once one factor has been altered, there needs to be a check with all the possibilities before giving the fork a clean bill of health.

So the issue is.... fork’s bent?

Andy’s got the right idea! :beer:

The promise of a supply of Belgian ales might convince me to finally acquire the old Park Tool fork vice and bender tools from the co-op. I seem to be one of few using them anyway.

Amen to that! That’s why I prefer slacking off at work whilst acquiring bike frames and parts in the hopes of one day putting them together.

Doug Fattic You addressed all of my thoughts and questions regarding all of the factors one needs to consider when carrying out a fork repair. For example, If both blades of the the fork are bent backwards but aren’t bent equal amounts, how does one determine the correct angles? If the blades are then bent back into roughly the proper angles does one rely on the eyeball gauge to say the angles and curvature are correct? I know there’s math and stuff but would a better question be, “What do you want? Comfort? Sharp steering? Style points?”

I hope I’m making sense. Probably not but a guy can hope!

The amount of curve (defined as rake) on the fork is based on the head angle of the frame (and tire size). The frame designer choses how much rake he wants to get the right amount of "trail". For example if a frame has a 72º head angle and 700C X 28 tires, it is likely that the designer chose a 50mm or 2" rake. This will give a trail number of around 59mm. Google the term if you don't understand what all this means. This is part of what determines how a bicycle will handle. This is what I meant when a frame builder has to do some research in order to know how to align the for/aft amount on the fork. He/she is not going by looks but rather by the numbers. The kind of curve (whether sharp or gradual) is mostly an aesthetic choice. Now it is possible the head angle can't be measured and one has to go by clues on the fork. In that case he will eyeball to see if the straight part of the fork blade lines up with the steerer. Of course in an accident some of the curve may be lost so that is not the best approach.

I have special tools that help me know which direction the blade needs to pulled to get it into alignment. it is always helpful to have the frame available to check the head angle to better guess what the fork rake is supposed to be. I've never bothered to try and figure out a home made way to check alignment. I don't have the need myself. When I am aligning a fork, I hold the fork with a wood block in the machinist vise on my workbench. I turn the fork so that I am always pulling the fork blade towards me (often with the help of my foot on the bench to give me more power and with gloves so the effort doesn't hurt my hands). It is a back and forth process to the fixtures until everything is aligned.
https://cimg4.ibsrv.net/gimg/bikefor...24131e1e8.jpeg
One of my frame building class students aligning a Schwann Super Sport frame from the 70's. It can take some effort to pull some blades straight.

https://cimg5.ibsrv.net/gimg/bikefor...e0184cf7d.jpeg
I have 3 fork fixtures in this picture. My most accurate one is in front of the speaker standing upright. Look closely and you can see the carved lugs I did for a frame for my nephew
https://cimg0.ibsrv.net/gimg/bikefor...8ea3f2b3e.jpeg
Using Campy "H" tools to align the dropouts.

When one fork is bent more than another, I clamp a straight stick across the crown and use another straight stick placed across the forks at various stations all the way to the dropouts and eyeball for parallelism. Then, push, pull, lever, pry, depending on your tools. I use a big two screw wood clamp to fix the fork to the workbench at the correct place and a piece of pipe over the fork for leverage at the correct place and lift. When it looks good, I put in my good wheel. If that looks good, I put the fork back in the frame and ride. If it pulls one way, I go back and try again. It is easiest to do this with caged HS bearings:)