Loose lower cup

I have Vitus 979 fitted with a Shimano 600 HP-6400 headset, and have been fighting a loose headset for some time now. The problem is that once you tighten the headset top cup and locknut until it is tight enough to have no hand-on-brake-rock-back-and-forth play in it, then its too tight and is notchy and horrible to ride. There's none of the 'middle ground' between too tight and too loose that all the how-to guides say there normally is.
So I had a look and have found that the bottom cup has a hairline crack in it. I think this is more a consequence rather the the root cause, although doesn't help. I also found the bottom cup is loose in the headtube!! And in doing a little research, gather that the headset could be the wrong type, being JIS instead of ISO.

Can anyone suggest what I need to do to fix this? I presume a new headset, but If I have the wrong type I want to know what is good to replace it with.

Thanks.

Try a shim from an aluminium can for the lower cup? May need a spot of glue to secure it. I've heard something like this can be used but can't vouch for it: http://www.screwfix.com/p/aluminium-foi ... -45m/50629

The concern really though is the hairline crack - that is only going one way and that's to develop further?

Its sounds like its been ridden with the headset to tight, hence the cracked cup. If its been to tight it could also 'brinelled'. You would see little indentations where the bearings have worn the cups, that will make it near impossible to get to run smoothly without any play.

I'd buy a new headset. The ISO/ JIS difference is the crown race but pound to a penny yours is Euro. No need to spend a fortune if you don't want to.

Shaun

Re:

No brinelling, but no doubt I did crack the cup myself. I have just removed the HS and found the headtube looks like the ID is bigger at the top and bottom where the lower cup and top race fit. The top race also came out with my fingers. Does this suggest it has been reamed? I know the previous owner of the frame used a Campagnolo Chorus headset. Perhaps it was reamed larger and now the Shimano headset won't fit tightly? What is the difference in Campagnolo and Shimano head tube inside diameters?

I'd start with a pair of vernier calipers and take some measurements so you can establish the cup size you need. If the frame has been altered previously then it doesn't matter what headset you have or buy, it needs to fit the tube as is.

The cup OD should be 30.2mm for Campag and shimano (plus all the rest).

Some cups were notoriously small like EDCO but still were the nominal size and fitted. Have you got an old headset knocking around?

Shaun

You really need to check and measure. The classic Campagnolo size for headsets is a crown race size of 26.4 and a cup outside diameter of 30.2. Shimano 600 will do 2 sizes, either the std 26.4/30.2 or 27.0 crown race and 30.0 cups.

A 30.0 cup will normally just push in and often fall out of a head tube that has been milled to accept a 30.2 cup.

If a 30.0 cup has been used in a 30.2 head tube then it will have been slack and the headset probably over tightened in an attempt to remove the play.

Sorry, blonde moment, forgot that JIS cups were 30.0mm. Mr Shinkicker has less memory problems than me!

Shaun