You could look at Planet X free ranger frame set. it is supposed to clear 48c with 700c
mine clears 52-584 barzo and 45-622 without mudguards
I cleared 50-584 and 42-622 with mud guards (I haven't tried 52-584 yet)
The Tempest (TI frame) is supposed to have the same clearances. Being Ti, is supposed to be more comfy and outside routing makes the assembly and maintenance much simpler.
They will have a steel frame set soon