You need some long reach brakes. Make sure you measure first so you get the right reach. That is big enough that you might need either a drop bolt rig or a BMX style long reach caliper.
Measure the reach from the center of the brake mount to the center of the rim on the braking surface.
ahh im having the same problem on a townie bike build ive been working on too long.
currently i am searching for a later model 700c fork made for short-reach brakes. since i already bought a brakeset. personally, i think that would be the best fix, since you can probably pick up decent short-reach brakes fairly cheap off ebay or bargain bins. i got a set of veloce brakes for $30 shipped.
[quote=“Daft Monk”]Tektro makes some long reach brake calipers called R556. They have a reach of 55-73mm. [/quote]
Daft Monk wins. These are your solution.
Just sold a set of r556’s to a guy yesterday who had a similar situation. Measure first, of course, but those should be a swell solution. And at only 17 bucks or so a piece, they’re a fine value, I reckon.
A set of Kool Stops makes them even finer. The other danger is that the fork is drilled for a nutted brake rather than the more modern recessed brake bolt. If that is the case you may need to drill.
On my ex-conversion (a late 70s Nishiki International) I had to run 700c wheels in 27" spaces; I had the same gap as the OP. The Tektros didn’t reach, I had to get the Cane Creek SCR-3Ls (or something like that, it’s a long version of a standard Cane Creek caliper.)
shrug
Edit: here’s a pic so you can see the gap I had to make the brakes reach across: