+1...
And I'd regularly inspect all 4 bolts holding the subframe to the backbones for proper torque, as their known to come loose over years and years of (too heavy) topcase-rattle...
A torque wrench and a drop of thread-lock deals with the issue ;-)
The easiest (and FOC!) countermeasure seems to keep your topcase payload at bay and within the
MFG recommendations of 6.5kg/14.3lbs nett or
10.0kg/22.0lbs gross weight...
(brief observation of driving physics should prohibit one from placing
weight that
high and that
far aft on a motorcycle anyway;
heavy stuff is to be packed as
low and forward as possible...always...)
And IMHO is ST Gui on the right track with his remark about lateral movement (shape and kind of material fracture enforces that argument):
cracked subframes seem to occur almost exclusively due use of unsuspended after-market topcases/racks, whilst I've never seen one coming apart in such matter when an OEM carrier plate with lateral damping is installed; food for thoughts...
Last but not least my very own experience in this issue:
- I'm using the OEM carrier plate with lateral suspension
- I never leave the topcase on the motorcycle when not needed/riding solo/commuting...
- On tour I only pack the very
lightweight items there: his/hers thermal liners/fleece-jacket, spare gloves, balaclavas, a hand full of road-maps, mandatory roll of toilet-tissue/wet-wipes...
never suffered a broken subframe ever... go figure...