knocking in the bb

bluechair84

I can ever so slightly rock either crank arm which when riding is a nasty knock when honking. Could it be the external bearings or the cranks not tight enough? Which part is most likely before i start stripping?
cheers

Vivid

If you can rock both cranks your bottom bracket has play and either needs to be adjusted or replaced.

What BB is it?

bluechair84

shimano xt external bb...
gonna strip it tonight but once i get the cranks off i might not be able to isolate the fault