shimano hollow tech II bottom bracket cups
Having recently put a bike together for the first time, i then realised that i'd left the inner cover from the bottom bracket out when i put the cups in the frame!
I was following the park tools webpage at the time, and since their diagram didn't show the inner cover present, i'd assumed it was just for holding the thing together during transport/sale
So, my question is this: is the inner cover absolutely necessary? I guess it's job is to keep grit and rubbish from falling onto the spindle and into the bearings, but would the cranks die a sudden death without the cover??