most 40gbase-SR4 optics are rated for 125M of OM4 no problem, I'd imagine if you have good optics, fiber, and clean it properly beforehand 140m wouldn't cause a lot of issuesWhat side effects do i have to face, if the uplink connection of stacking members will exceed the 100m limit ? Losing stack members, lost packets ? I want to stack one member using a 140m multimode cable, otherwise i just can stack the cores and use regular LAGs.
if you go over that or use worse fiber and you get connection drops, it depends how you've cabled it. stack members should be connected with 2 runs (like a ring), so if it loses one connection it just fails over to the other. If you lose both links then obviously you'll get some packet loss to destinations on that switch, and if they both go down for longer the stack member will eventually be counted as lost until the stack master sees it again