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 Post subject: Head tube issues
PostPosted: Tue Aug 20, 2013 6:37 pm 
retrobike rider
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Location: Birkenhead
Quick query for the more mechanical minded members on here (ie virtually everybody bar me!)...

On my P7 I've had two different sets of forks and two different headsets (threaded and threadless) all fitted correctly, but there is a slight 'wobble' when rocked back and forward with the brake, or when lifted up at the front end by the stem, for example, there's another slight movement noticeable. All bolts are tightened and everything's greased up 'n all..

Head tube "looks" fine too but I assume that's where the problem lies?

Any ideas? :?


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 Post subject: Re: Head tube issues
PostPosted: Tue Aug 20, 2013 6:48 pm 
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Brake rocking is quite common. What forks are you running as some forks also produce a wobble, especially old suspension. It could also just e the fork sag, unless rigid of course.

I had an issue where I replace everything from the headset, stem, bars and wheels and it still happened. Turned out to be the pace forks - something internal was clunking, in fact if memory serves it was the slider starting to unbond from the crown. A trip to pace was all it needed.

Oh, could just be the headset.


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 Post subject: Re: Head tube issues
PostPosted: Tue Aug 20, 2013 6:48 pm 
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Have you checked that the compression ring is seated properly in between the bearing races and the steerer tube- that's often a cause.
If you've got a set of calipers, you could check that the diametre of the headtube is consistent top to bottom.

The only times I've had that problem before with different h/sets is the crown race on the forks not quite matching with the lower race of the headset (esp with cartridge bearings). Sounds unlikely in this case as you've tried different forks and headsets, but if you have a couple of spare crown races and can pop the one on the forks off, maybe try that & see if it sorts it out?


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 Post subject: Re: Head tube issues
PostPosted: Tue Aug 20, 2013 6:53 pm 
retrobike rider
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As I say it's happened twice, same slight 'not quite right' feeling (not on any of my other bikes)

Now running pace rc36 (just fully refurbed by tim) with a brand new bbb headset threadless. Previously it was F7 forks with a threaded ritchey logic headset. Same movement pretty much. All 1" compatible etc, obviously.


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 Post subject: Re: Head tube issues
PostPosted: Tue Aug 20, 2013 11:46 pm 
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I did have an issue with my dynatech, a chris king and a few other headsets slipped in without too much fuss so had to hunt around for a headset that was slightly larger in diameter top and bottom. Not sure I ever felt any rocking though, just an uneasy feeling that the cups were an easy press fit rather than a solid and secure fit needing to be squeezed home with a headset press.

Just a silly thought, are the headset crown races a nice and tight fit on the fork?


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 Post subject: Re: Head tube issues
PostPosted: Wed Aug 21, 2013 6:33 am 
retrobike rider
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Thanks Ian, yeah everything DOES seem nice 'n tight which is adding to the confusion.

Put it down previously to using an old quill stem but gutted thats it happened again with a brand new set up :?

Will have to be a trip to the LBS.......

Good news is thats its still perfectly rideable, just that it should be ''rock solid'' up front and its not quite right..


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 Post subject: Re: Head tube issues
PostPosted: Wed Aug 21, 2013 6:58 am 
retrobike rider
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Watch the forks very closely when you rock the bike.

I have RC36's on my Fuquay and they start to sag almost as soon as you put any pressure on them, so when you rock the bike they depress and rebound a small amount, giving the impression that something is loose.


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 Post subject: Re: Head tube issues
PostPosted: Wed Aug 21, 2013 7:35 am 
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Location: Platsa, Messinias, Greece
You should be able to feel headset play simply by placing a fingertip on the cups as you rock the bike on the brake, similarly you can check play between the frame and the headset and between the fork stanchions and sliders.
If you try it with the wheel turned through 90 degrees do you notice any difference?

Did you fit the headset and, if so, how did the fit of the cups in the frame feel?
If you can't pin it down then strip the front end and check the fit of the cups in the frame, the fit of the crown race on the steerer tube (if not the split type),check the forks for stanchion/slider play and also check for undue play in the brake pivots.
As this is a threadless headset (presumably) do you have the top split compression ring in place?

Hardly much need for a trip to the LBS :?


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 Post subject: Re: Head tube issues
PostPosted: Wed Aug 21, 2013 7:49 am 
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Has it always felt like that? The fact that it's done the same thing with two different setups may mean it's something to do with the headtube, perhaps it needs reaming/facing? I did have to do this on a bike of mine with similar issues.


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 Post subject: Re: Head tube issues
PostPosted: Wed Aug 21, 2013 8:06 am 
retrobike rider / Gold Trader
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I had same problem on my C16R using threaded 1" headset, but found out i had run out of thread on the steerer of the forks, a couple more threads cut on the steerer sorted it, Basically i was tightening it up fully, nice and tight (or so i thought) but still had slight wobble. Both my Pace RC35's and the Original F7 forks looked identical in steerer length, but obviously there was slight differences in the way the crown race sat on the forks, and the headset once all assembled. As for threadless not sure other than whats mentioned above, as your using threadless i am guessing the Star Fangled nut is nice and secure in the fork steerer?


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