A Day rack, designed for a narrow, tall but not very long bag. It cantilevers from a plastic-sleeved tube over the suspension housing and the rack mount.
A Big rack, designed to be used with a racktop bag or in combination with a clipped-on TSR ‘Big bag’ with integral frame for touring loads. It bolts to the seatpost clamp and the rack mount only.
No specific issues with either rack but heavily overloading the big rack ‘naked’ might damage the rack. The naked rack certainly flexes once the load increases. The big bag frame triangulates the otherwise unsupported cantilever section. The designs have not changed over time EDIT: the earliest big bags used Karrimor pannier clips, replaced with another brand after Karrimor got bought out. No functional difference but the mounting clip at the seatpost has to be adjusted a couple of millimetres to interchange with later big bags.
We have both types here. HK prefers a racktop bag on the big rack for brevets. I prefer the discontinued Weekend bag on the day rack.
