Bicycle Mechanics - Headset Race Fit Problem-is this common? intro!
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01-04-06, 04:26 PM
Hey everyone this is my first post. Nice to meet you.
I have a used threaded Campy headset that I am pressing into an Italian Benotto track frame. Strangely, both head races slid into the headtube almost all the way and the crown race could almost be pushed on the fork by hand! I took the headset press to the head races and the lower head race is pressed into the headtube just fine but the upper head race can still be pulled out by hand with a little wiggling! Is this common? Didn't think so.The few headsets I've pressed in have been a very tight and precise fit.
My only thought is that this Super Record Campagnolo headset is J.I.S. sized?! What?! If that were the case what explains the proper fit of the lower head race and crown race?
What would happen if I chose to ride the bike with a upper headset race like this? I feel like the upper bearings and adjustable race would keep the upper race "pressed" in but if the race should come loose even by a fraction of a millimeter would I end up with a loose steerer and damaged headset?
01-04-06, 04:29 PM
the frame might wallow out in addition to the HS races being mangled.
in my experience (becuase I've done this...I'll ride almost anything) it feels crappy and rattly being loose like that, and depending on how loose it is the headset can possibly wear funny. I have never personally had it affect a steerer. Depending on how loose it is, and where you ride, long term damage to the head tube would seem more likely.
Back in the old days (i.e. when I was a kid) I'd take that top cup and put it over the nose of my dad's anvil and center punch a divot in about 4 to 6 places on the part that goes into the head tube. Those divots would then hold the cup in place. For a little while, anyway :D
01-04-06, 05:12 PM
I assume that you are dealing with 1" headsets/frames here. Before installing the headset it is a good idea to measure the headtube inner diameter and compare it to the headset cup outer diameter. Same for the race but measuring the fork crown race I.D. and fork crown base O.D. The headset cups should be .2mm larger than the frame's headtube inner diameter. The headset's crown race should be .1mm-.15mm smaller than the fork cron base. You are right that there are different standards of 1" with different size press fit surfaces. These standards are somettimes "mixed" between the frame and fork. The two most common size headtube inner diameters for 1" are 29.8mm and 30.0mm. The 2 most common size fork fork crown base outer diameters are 26.5mm and 27.2.
As far as the upper cup fitting differently than the lower, this can that the headset is defromed since you said it was used. It can also be that the frames lower headtube bore needs to be reamed at which point you will need a different headset. All this is kinf of confusing and I'm describing it poorly. Just make sure that you have the proper press fit tolerances, .2mm for cups nad .1mmm for fork race.
01-04-06, 05:26 PM
That's odd that the top cup is loose. I've only seen bottom cups get wiggly.
Others may have better advice, but the best solution I've found is to find a shop that has a knurling tool. It's a hinged, c-shaped thingy with two grooved wheels attached. It's used to add knurls (those ridged lines on some cheap handlebars where the stem attaches) to round pieces of metal. I've found that knurling a cup can push up enough material to make for a snug (but definitely not tight) fit. That and some Loc-Tite 640 might do the trick.
Be careful not to clamp the knurler down too hard or you'll crush the cup. Then it'll be even looser than when you started.
01-04-06, 05:46 PM
I thought so too. Its definitely a snug fit. Its snug enough to where if I turned the frame upside down and shook it violently the cup still wouldnt fall out. But I can definitely pull it out by hand with a little effort. I'll try loc-tite I guess. Thanks for the suggestion.
I'll probably just buy a new upper cup before trying out a knurling tool and if the new cup has the same problem, its probably the frame and I'll go with the knurling tool.
Is it also odd that the lower cup went about 3/4s of the way in before beginning to resist? The few other times I've pressed in cups, they wont go in but a millimeter or two before requiring the press, suggesting that the tolerances were pretty exact. I was almost able to press these in by hand. Thanks for the help.
01-04-06, 06:35 PM
Thanks guys. Unfortunately I don't have a caliper so I can't measure anything accurately. I'm going to try using a little loc-tite on the upper race and hope that helps the race stay in the head tube. If that doesn't work I'm going to try a new upper race (theres a few NOS ones on ebay.) I'm gonna refrain from punching divots in the race because its kind of a nice bike...but that sounds like an excellent idea for a less discriminating bicycle! Thanks for the help!
01-04-06, 08:44 PM
Punching divots is a good idea to use in combination with the loctite, provided you do it with a solid bar running through the race while you hammer the punch. It will cause no other deformation to the cup other than raising a small lip immediately around the punch mark.
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