"funny" feeling steering!

[Vs4b]

Bit hard to explain so bear with me...

Riding home i noticed a strange feeling on my bike, it seems to have developed a mind of its own when going around corners! I can be half way around a bend and the handlbars seem to nudge themselves back against my direction of turn. Its not loads of pressure but it does seem to be somehow notchy, as if i have a groove in which the bars sit rather than being free to move in all directions. Its certainly disconcerting and i suspect verging on dangerous at times. Does that make any sense as a description?? I've also noticed that at standstill it is slightly harder to start a trun of the bars, as if there is some pressure to overcome.

No doubt this is a normal problem that i've just never heard of and you all have, I hope so anyway! So can i have your opinions/guesses and predictions on what it is and how i fix it please? I've discounted the option of the bike being haunted already
Thanks!

[zigzag]

headset bearings (or whole headset, depending on the type) need replacing. there are indentations now in the races in the most common position, when the wheel is pointing straight ahead, and that's where the bearings "slot" in.

[jsabine]

Sounds like 'indexed' steering - Sheldon explains it better than I can, about halfway down http://sheldonbrown.com/headsets.html

[Biggsy]

Another cause of self-centering is bent back forks from frontal impact, but it's bound to be the headset if you can feel a definite notch when lifting the front of the bike and steering lightly.  If non cartridge, re-greasing will make it a bit better for a short while, if you want to do something before the replacement bearings/headset arrive.

[Kim]

It does sound like notchy headset - easily confirmed by lifting the wheel off the ground and feeling the steering action.  If you have to replace it, make sure you fit one that uses cartridge bearings - they make the whole process a lot less painful in future.

Alternatively, if it's a folding bike, make sure it's not trying to fold itself up as you're riding along!  (This happened to someone with a Brompton on the unofficial FNRttC to Brighton last week.  I was impressed she was able to ride at all with the hinge undone.)

Other things might be loose axle, very slack spokes, flat tyre (you'd surely notice) or seriously wrong forks...

[T42]

Apparently the pukka term is "brinelled", rather unjustly named for the chappie who conducted the first formal investigation of the effect of pressing balls into metal.

[Biggsy]

This is academic, but Jobst Brandt argues that it's caused by fretting from lubrication failure (known as "false brinelling"), rather than actual brinelling (a kind of hammering).  http://sheldonbrown.com/brandt/indexed-steering.html

I'd argue that "buggered" is an adequate technical term (although perhaps this implies a kind of hammering as well!).

I agree with replacing conventional headsets for cartridge bearing ones (except in rare cases when the tolerance of a Campag bb headset is useful for dodgy head tube faces or whatever).

[andrew_s]

Most non-cartridge headset bearings us balls held in clips. Swapping the clipped bearings for loose ones of the same size will usually fix indexed steering for a while as the ball spacing will no longer match up with the indentation spacing.

[Vs4b]

Thanks everyone. Now I shall see what needs buying and or get it to the shop again... Nice to know that once again the site has provided the knowledge I lack!