Bicycle Mechanics - Split Crown Race

Hey all, I picked up a used frame/fork recently, and noticed that the crown race was split. It looks really clean, and if I didn't know anything I'd think it was supposed to be there, but since I know just a smidge more than nothing I thought it would be best to ask. It's an FSA headset on a Scott CR1 Pro. Thanks for the help in advance.

Brian

Normal. FSA supplies split crown races on several of their cartridge bearing headset models since they can be installed with no tools.

+1
HR ain't pullin' your leg

I wish they were all split.

Awesome guys, thanks a lot. That puts me a bit more at ease, haha.

sorry to dredge up an old thread here, but I found the same thing on a circa 1987 Shimano 105 crown race. I've never seen one split like that (or noticed) before, but I haven't closely examined 100s of headsets either. I'm having trouble getting the headset (1" threaded steerer...again, circa 1987) adjusted with no fore/aft play, but the correct turning resistance...I figured it was the split in the crown race or worn out bearings (or both). I might pick up a handful of 5/32" loose bearings if a split in the race may be a factory thing. It looks very clean/machined...so if it's a stress crack, it's a darned clean one! (I should have taken a picture, sorry)

sorry to dredge up an old thread here, but I found the same thing on a circa 1987 Shimano 105 crown race. I've never seen one split like that (or noticed) before, but I haven't closely examined 100s of headsets either. I'm having trouble getting the headset (1" threaded steerer...again, circa 1987) adjusted with no fore/aft play, but the correct turning resistance...I figured it was the split in the crown race or worn out bearings (or both). I might pick up a handful of 5/32" loose bearings if a split in the race may be a factory thing. It looks very clean/machined...so if it's a stress crack, it's a darned clean one! (I should have taken a picture, sorry)

Take a caliper and carefully measure your head tube both front-to-back and side-to-side. If the front-to-back measurement is a tad oversize, you have an ovalized head tube. That's the result of riding with a too loose headset. It's semi-common on older bikes.

you're talking about measuring the head tube itself with the headset removed, correct?

I'm doubting that because it's not been loose. One evening on a cooler (ie, 50s/60s F) ride, it developed a bit of a "notch" in the centered position. I figured the bearings were gummed up and colder than usual so I took it apart yesterday, cleaned everything & re-packed it. Since then, it's seemed like there's no sweet spot of adjustment with no fore/aft but still with free rotation. Prior to that, it rotated freely except that it seemed to want to stop on the centered position, but had no fore/aft play at all.

The "notch" is a classic symptom that the bearing races are worn in spots (specifically the spots that the bearings sit in with the wheel straight ahead.) Often happens if the headset is run too tight.

Some people report alleviating the problem by replacing bearing retainers with loose balls, or rotating the cups by 90 degrees in the frame; these might help but are temporary solutions IMO.

that makes sense. I picked up some more 5/32" bearings this afternoon & I'll try them. I had something similar in a very well-worn MTB I rejuvenated a few months ago...but it was generally notchy more than centered on any particular point. On that bike replaced that one with loose balls top & bottom (more to see if it would make a difference & give myself a real stark before/after comparison)...and, barring another rode-hard-put-up-wet 20 years that bike had between 1987-2009, I'd fetch a guess it's good for another 20 years as a tank of an urban assault bike...in other words, it's veeeeeerrrrrrryyyyy smooth. So, that's a long way of saying maybe I could expect the same result here?

Also...so, a split crown race may be a factory thing for this headset?

(OK, promise not to belabor it any longer...if the new bearings to smooth it up, I'll pick up a new headset + the tools I need to change it properly)

New bearings also, do not fix pitted headset cups.

I don't know what the deal is with the split crown race. If it's not a cartridge headset and the bearings are running directly on the crown race it doesn't sound right. Pic?

OK...guess I lied...still adding to the thread....Here's what it looks like. Using a some jewelers lenses, I could see some definite wear on the race, but it still looks like a nice clean crack. Guess my only question - more academic really - is whether it could have been made this way. Thinking about it, I can't imagine how it could be & be expected to work smoothly over time....

http://i256.photobucket.com/albums/hh164/cgfiat/105headset2.jpg

http://i256.photobucket.com/albums/hh164/cgfiat/105headset1.jpg

That split isn't "factory", it's damage. Loose ball headsets do not come with split crown races, they are only provided on some cartridge bearing headsets.

That split isn't "factory", it's damage. Loose ball headsets do not come with split crown races, they are only provided on some cartridge bearing headsets.

I've never seen a split race that's split so precisely like that...

guess i've learned something new today, so I can go to bed :)

I've never seen a split race that's split so precisely like that...
I have. Years ago I had the crown race on a Shimano XT headset (loose ball, not cartridge bearing) split just that cleanly so it can happen.

If the crown race is simply a seat for the inner race of a cartridge bearing, the split doesn't matter, and might even be designed in, working similarly to the split centering cone at the top of threadless headsets.

If the crown race is the actual inner bearing race as in most loose ball headsets the split is probably the result of being installed over an oversized crown. Crown races are through hardened, and have little capability for expansion when forced on. The crack will cause a slight click as the balls run over it, and will lead to degradation of the headset. It should be replaced, after properly sizing the crown race seat.

yes, the riding symptoms reflected that 'click', so that makes good sense. Interestingly - or not - this is the original headset for the bike...well, I guess unless someone between about 1987 & now replaced the headset with one from the same group (and period) but used a 26.4mm instead of 27" set....maybe? Whatever the case, it makes sense to me now so a replacement is about to be on its way & a proper press/installer fabricated. Thanks all.

I have a Campy SR head set with a split CR. I can't feel anything. I locate the split to the rear where the forces are minimal. Smooth as butter and a lot cheaper that buying a used headset for >$80 just for the CR!

I believe it happened upon installation in 1983. The difference between the ID and OD was creater than spec due to the paint overspray on the crown. I cleaned it up and reinstalled and still don't feel it.

http://i985.photobucket.com/albums/ae332/SJX426/1983%20Colnago%20Superissimo/Cleaned%20Up%20Colnago/P9261342.jpg

I was thinking that there's no urgency to replace those cracked crown races if you don't want to. It's not like a hub or bb in which the bearings are actually spinning .... they just sit there, moving slightly when you turn.

hmmm...hadn't really thought of that one. I could do that simply enough, but then again mine's not an >$80 part. If you *were* to select a location for the crack, would it be in the rear? a side? or just anywhere but right in the center?

hmmm...hadn't really thought of that one. I could do that simply enough, but then again mine's not an >$80 part. If you *were* to select a location for the crack, would it be in the rear? a side? or just anywhere but right in the center?

I don't think it matters where the crack goes. Ideally you wouldn't want a ball bearing on when riding forward, but I don't think you can control that by the time everything's put together & adjusted.

I assume the front center is the point of highest stress on the race, considering the angle of the headtube (and loc of crack in my fork's case)...yes?

I've never seen a split race that's split so precisely like that...

I have. Years ago I had the crown race on a Shimano XT headset (loose ball, not cartridge bearing) split just that cleanly so it can happen.
I have too. On a 1982 Schwinn, which unfortunately used a non-standard headset design so I had to make do with still using the race.

In my case the split was lined up with the edge of the fork crown. I rotated the race so that the crack was over one side of the crown, where it would not experience shear force.

I positioned mine where there was the least likely to have compressive stress, the rear. Shear force? What shear? The cr is fully supported by the crown. The bearings are point loads so there is no shear that I can see. The only compression the back experiences is going over bumps or braking. Locating the crack on the side allows for compressive stress during turning, left turn left side.