Hi just two more questions on the Headset ,

When should you know it needs to be replaced outright and when should it be a case of just changing the bearings ?The headset I have is very grainy to steer despite being well greased ,it doesnt adjust very well and there seems to be some wear on the crown race .Im sure its all put together properly and the bearings are in correctly .

What are common headset bearing sizes? . I bought some 5/32 inch bearings in races and they were much bigger than the ones in my headset .I dont have a callipers unfortunately to measure but are there many common sizes down from this?The bearings are in cages that are themselves in containers that can be pried open to put in grease ,the containers then sit in the cups of the headset .The headset is a classic External cup threadless headset .

Thanks for any help