Head Tube/forks 'locking' into place

[NorthernSky]

hi folks

I had my bike in a roof rack. I was doing silly speeds to a sportive I was late for
well since that I've encountered a strange problem

how do I describe this: if you turn the handle bars, when you get to the centre they seem to jerk and lock into place (straight on)
I can still ride the bike, but you feel it every now and again
what could cause this?
there is nothing obvious on the outside
have I done something to the bearings?

thanks

 

[MisterStan]

It sounds like you need new headset bearings.

 

[Yellow Saddle]

Your headset bearings are indexed. It happened gradually, not on your way to anywhere. It is a design fault with threaded headsets and a problem that was largely eliminated with the advent of the Aheadset.

Like Mister Stan says, replace the headset.

 

[NorthernSky]

ok thanks, are they easy to fit?

 

[lpretro1]

It can happen with any headset bearing that is left unloved for too long - threaded/unthreaded/loose ball/cartridge ...

 

[NorthernSky]

Can you take a photo and put it on here?

 

[Yellow Saddle]

It can happen with any headset bearing that is left unloved for too long - threaded/unthreaded/loose ball/cartridge ...

No, it doesn't work like that.

 

[Yellow Saddle]

View attachment 93314

In your case you have a cartridge type headset and you only have to fit new bearings. Measuring and sourcing the bearings requires a bit of know-how, as does fitting them. I suggest you get your bike shop to do it for you.

However, something else is amiss. Because this is not an old-style threaded headset and the symptoms you describe is what happens to threaded headsets over time, your headset was damaged in another way, probably vibration damage. For what distance was this bike on the roof and mounted in what way?

 

[Soltydog]

Mine is like that on my tourer & has been since new. I just thought it was a quirky design feature

 

[rualexander]

Your headset bearings are indexed. It happened gradually, not on your way to anywhere. It is a design fault with threaded headsets and a problem that was largely eliminated with the advent of the Aheadset.

Like Mister Stan says, replace the headset.

Happens with threadless Ahead type headsets too

 

[Drago]

The slipstream from a car at speed can strip the grease out of a headset bearing on a roof mounted bike. If the bearings are a bit worn already then the lack of lube will highlight the problem. Tie a rag around the headset next time.

 

[Soltydog]

If it has been like it from new, I would look to see if it is the cables having a point where their tensions are in equilibrium.

I reckon it is certainly the headset/bearings. Last year I stripped it & re-greased the bearings & the 'locking' went away for a short while, but returned. But it's something I'll look at

 

[Yellow Saddle]

Threaded headsets were very prone to indexing not because of the threads per se, but because of the way the bearings races were mounted rigidly onto the fork and frame. Fore/aft flex of the steerer at the lower headset bearing caused a fretting motion (as opposed to rolling motion) between the balls and races in straight-ahead riding. This caused the grease to be pushed out from between the balls and races and naked steel-on-steel fretted and eroded away the metal on the race. This erosion is actually micro-welds from friction-welding that welded and broke away in quick succession until the races were dented. These dents are always more pronounced in the plane of riding I,e, in front and back.
The threadless headset invented by Aheadset, largely eliminated this problem by allowing loose bearing cartridges with chamfered edges to slide and move against the frame and eliminate the fretting. Also, most Aheadset style headsets are mounted on larger diameter steerers (1 1/8th vs 1") which reduced the flex and resultant unnatural bearing movement.

This same effect can happen when a headset is slightly loose and then vibrated for an extended period of time, such as when on a car roof. That situation would simulate and exaggerate the movement and very quickly erode the races, whether it is a threaded or non-threaded headset. It is not so much the rain stripping the grease away but the small oscillations of the bearing rather than full rotation, that pushes the grease aside.

Car wheel bearings have the same problem when cars are lashed and transported for long distances on railway carriages. Special precautions have to be taken, such as overtightening the bearings, before such trips are undertaken.

 

[Yellow Saddle]

Another thought is that it could be that the two races are not quite parallel to each other.

The symptoms don't suggest that problem. When the headset is incorrectly fitted and not parallel, the symptoms display as a steering that is loose in some positions and tight in others, but not notchy.

 

[Yellow Saddle]

It would still tend to sit away from the tight though.

Hmmmmm. Not so sure. When a headset is indexed, it snaps in place with a visible snappy movement. When it "sits away from the tight" it is more gradual and linear. The OP describes otherwise.