Woah. Hang on. Can I just rebuild my wheels to 18" and put knobblies on? What ab out clearance? Do the brakes still work, or do you have to switch to discs?
As long you removed the mudguard, and yes you need discs.
Only if you use a skimpy tyre like a kojak, Vincent (Eerder metaal) produces forks and rear frames to suit, with longer stays so you can use 18” and a decent tyre..
No point fitting a new triangle and wanting to use 18” but not making it a little longer IMO
As long you removed the mudguard, and yes you need discs.