some racks like Tubus, include a mount on the rack, for mudguards, separately..
... so you mount the rack on the bike, then mount the mudguard struts on the rack.
Longer bolts & spacers can gain width on a frame that may take a non disc rack but still need a little more clearance..
....
Last edited by fietsbob; 08-17-17 at 08:26 AM.