This Campy Veloce headset is driving me nuts!

[smead]

Merckx frame came with a smooth Veloce threaded HS and after a few rides, it got notchy. So I serviced it. I swear it is reassembled correctly. And I've done more than a few new threaded headsets and repacks. I have never had a problem. Til now.

When I thread the top cup down on the fork to get the right preload, all feels normal. If I thread all the way until it stops, the steerer is stiff, but smooth (just repacked bearings which all looked good as did the races). So following my normal routine, I then back it out just until steerer turns freely, just to the point of having play. At that point, it turns smooth and easily - so far so good. The last step is to then hold that cup with one wrench, and tighten the lock nut to lock it in. So long as the cup doesn't move, this should not change the preload much, if at all. But it does - a lot!? If I just hand tighten the lock nut, it gets stiff. If I tighten it down more to proper torque, it hardly even turns!?

I'm stumped as to how securing the top cap could change the preload like this unless the cup underneath spins with it, which it does not. If a bearing or spacer was installed wrong, it would bind when I first tighten the top cap. It only gets really tight when I synch down the lock not.

What am I missing ?

Was thinking I'd just get a new record HS as they are cheap enough, but this Veloce has a low stack (33), and the record and DA and most others are 36-38. Anyone have a silver CK threaded HS they want to part with?

[Pastashop]

Have you checked that the threads in the threaded cup actually hold?.. one possibility is that the threads have stripped enough there that the lock-nut just presses it down and loads the bearings.

[smead]

Originally Posted by Pastashop

Have you checked that the threads in the threaded cup actually hold?.. one possibility is that the threads have stripped enough there that the lock-nut just presses it down and loads the bearings.

Yep that's a good thought, I'll double check tonight, but I'm almost sure the threads in the cup are solid as I can thread it all the way out, back on again, spins smooth ..

[cinema]

this isn't just you. i have this problem with current gen threaded campy headsets. too little, the HS develops play. Too much the headset is not perfectly free. I settled for a minimum amount of resistance. I want to get rid of the thing though. I did not have this problem with older ones or any other headset for that matter. I'm hoping this could be a grease/bearing break in period as i've only had it for around 500 miles.

All threaded headsets will add additional load once finally torqued down. you need to leave it slightly loose before adding the final torque on the top cap. i read about this for hours after experiencing the same issue.

for what it's worth i'm using a new record headset.

[Nomadmax]

To truly lock up a threaded headset and minimize or eliminate the preload increase you have to tighten the nuts toward each other.

[Mark McM]

Originally Posted by smead

I'm stumped as to how securing the top cap could change the preload like this unless the cup underneath spins with it, which it does not. If a bearing or spacer was installed wrong, it would bind when I first tighten the top cap. It only gets really tight when I synch down the lock not.

What am I missing ?

The thing you are not accounting for is that threaded fasteners have a clearance fit - the size of the internal threads is smaller than the size of the external threads. In other words, there is a purposely built in gap between surfaces of the internal and external threads. If theaded fasteners didn't have clearance fits, they would have excess friction when turning, and if they weren't formed precisely, they might not turn at all. Threaded parts are built with different amounts of clearance, refered to as their class of fit (the tighter the fit, the more precisely the threads have to be formed, because they have less tolerance for irregularities in the threads).

Because of the thread clearances, the position of the top race on the steerer threads can shift, depending on the direction it is loaded. When you initially pre-load the bearings, the top race is pushed upward (top surfaces of the race threads pressed against the bottom surface of the steerer threads). When you tighten the locknut against the top race, the top race is pushed downward, and the race shifts downwards (bottom surfaces of the race threads now press against the top surfaces of the steerer threads). The distance the race shifts downward when the locknut is tightened will depend on the clearance gap between the race and steerer threads. And obviously, if the top race shifts downward, it will tighten the bearing pre-load.

To account for the thread clearances, after initially setting the bearing pre-load, you need to back out the race slightly, to account for the thread clearance (and the amount the top race will shift when the top nut is tightened). Finding the right amount to back the top race out can be a trial and error process.

[smead]

Thanks, good advice, but all I can say is that is pretty much what I am doing and have always done on other threaded headsets or cup and cone bearings. This is not a fine tuning thing, but something different. I can back the cup out 1/4 turn until it has a bunch of slop, then hold it, and when I tighten down the lock nut, steering becomes stiff. It does almost seem like the cup threads are toast like the first responder said and it just pushes down when the locknut goes down. I'll try again later, something's not right ..

[smead]

Originally Posted by Nomadmax

To truly lock up a threaded headset and minimize or eliminate the preload increase you have to tighten the nuts toward each other.

Yep that's what I do!

[Mark McM]

Originally Posted by smead

Thanks, good advice, but all I can say is that is pretty much what I am doing and have always done on other threaded headsets or cup and cone bearings. This is not a fine tuning thing, but something different. I can back the cup out 1/4 turn until it has a bunch of slop, then hold it, and when I tighten down the lock nut, steering becomes stiff. It does almost seem like the cup threads are toast like the first responder said and it just pushes down when the locknut goes down. I'll try again later, something's not right ..

Yes, if the top race threads are stripped, you'll never be able to tighen the locknut without loading the bears. Another possibility is the top race is split (cracked).

Try this: uscrew the top race a full turn or two, so there is a clear gap between the race and the bearings. Then holding race (so it doesn't turn) and tighten the locknut against the race. Does the locknut tighten normally, or does it feel mush? Can you tight the locknut, while still leaving a gap between the race and the bearings? (it might be best to completey remove the fork to try this experiment). If the locknut just keeps pushing the race down, then the race threads (or maybe the steerer threads) are damaged.

[Ralph]

If wouldn't bother me if the steering was a tad "stiff" when bike is unloaded. I would figure it would be about right with my weight on bike. Assuming it didn't loosen up too much as I rode bike.

[cinema]

Originally Posted by Ralph

If wouldn't bother me if the steering was a tad "stiff" when bike is unloaded. I would figure it would be about right with my weight on bike. Assuming it didn't loosen up too much as I rode bike.

this is where i'm at with my campy hs. i have the same issue as the op. as mark mentioned, torquing the lock nut always adds preload and one must back off the race initially, which i've made a practice of doing.