I am a recumbent homebuilder. My road riding is mainly done on upright traditional road bike now since my area is really hilly and i am alone with a recumbent here.
My road bike is an old japanese (Univega) bike. I like it a lot. A lot more now with 34-48 chainrings with 12-30 9 speeds cassette. With this gearing configuration, this damn bike want to go place he never went before. It is pushing me on gravel road and try to direct me to light trail.
To help it a bit on tougher road (gravel), I'd like to being able to switch wheels and tire size when needed. Can't do it right now with caliper brakes.
It would be easy for me to brazed brake post onto fork and frame. Frame would give as much clearance as needed (brazing a new bridge). Fork would give me enough clearance for a 700 X 30 cross tire but not enough for a 700 X 35 road tire. I really like those 35mm Maxxis Euro Plus (on my single speed touring / cross bike) tires! Maybe i could get a custom fork BUT How long is needed to clear a 700 X 35? I think it could only work if it didn't throw off front end geometry.
Right now: head tube angle = 73.3, seat tube angle = 74, fork lenght = 369mm, bb height = 265mm
If i put a 10mm longer fork i get: head tube angle = 73, seat tube angle = 73.5, fork lenght = 379mm, bb height = 270mm (10mm block under front wheel for testing purpose).
Since i don't want a real cross bike, are those number acceptable for a road bike ( mainly used with 700 * 28 road tires, a little bit on 700 * 35 [32 mm real size] supple road tires and a little bit on 700 X 30 cross tires) ?
Solution 1 for me would be finding a used steel road fork with the right lenght and braze brake post. Solution 2 would be let someone else (i am not ready to build fork yet) build me a 1 inch ahead fork.
The cheapest thing to do would be to find an old (70's to early 80's) touring bike and use that fork. In our area (Northeast Wisconsin) they are a dime a dozen at garage sales and police auctiions. Most of them used 27" wheels with 1 1/4" or 1 3/8" tires (630 x 32 or 35) as opposed to the 622 x 28 tires you have now so you would have plenty or clearance. There were lots and lots of different brands with forks that would be adequate for your needs, many would have long reach caliper brakes that would fit over the bigger tires you want to use. I doubt that you would even notice the change in headtube angle or trail.