adlai

There is no other explanation.

I am trying to install the fork on the frame. Put the crown race on it.

It goes down the tube fine until the final inch or so. The tube gets a little thicker, by millimeters, almost negligible but enough to make it difficult.

If I try and force the crown race onto it, the crown race will actually be a little too big for cups, due to expansion.

What so I do? This is a modern 1 1/8 fork. Do I put a spacer there? Get a different headset? Shave some material off of the fork (looks very difficult)?

FBinNY 

The crown race is intended to be an interference fit on the steerer. Ideally the fork's bulged area (crown race seat) will only be a bit taller than the crown race itself, so you don't have to waste extra time and effort driving it home.

Don't worry about the race expanding, it's made of a hard grade of steel, and whatever expansion happens was engineered in.

To install properly you need a tool which is basically a pipe with a square face, and an ID big enough to slip over the steerer. It's used as a slide hammer to drive the race to the bottom. (yes, this is an easy tool to make yourself)

BTW- some crown race installer tools have IDs very close to the 1-1/8" steerer and end up binding when they encounter the bulge. Test for this before actually trying to press on the race. If it's an issue, use some spacers.

hueyhoolihan

don't sweat it. i JUST purchased a new CF frame/fork and, like you, had trouble getting the lower race on the steerer. too much carbon! took a file to the steerer tube where the crown race goes, and when i found that i could make some headway when putting in on by hand. i pounded it home. i'm pretty sure that with a little more whittling, i could have pushed it all the way home without any pounding at all. i've had it out for about 100 miles now and the headset is working fine! good luck.

if yours is not carbon, i suppose you can take some wet/dry sandpaper to the inside of the crown race or the outside of the fork. this might take a while depending on how much extra material needs to be removed.

BTW, i don't think that the race is really a race in the traditional sense that ball bearings contact it directly, assuming that you have cartridge bearings. it's more, in my mind, a device to insure that the fork/steerer tube rides on the inside race of the cartridge bearing and avoids all contact with the headtube, similar to the purpose of what's commonly called a compression ring at the top.

FBinNY 

And good luck to you. Not saying that failure and death is imminent, but this is most certainly not how this job is done.

IME the carbon steerers are true to intended size and shouldn't need any adjustment. If in doubt -- measure. The OD of the steerer should be about 0.05mm (0.09max) LARGER than the ID of the crown race. If the steerer is out of tolerance, the smart move is to return the fork as defective.

IN any case, THINK before making any modification. The crown zone of a steerer is possibly the most stressed part of a frame. It's also the place where failure could have the greatest, most dire consequences. So this is not someplace one should fool with unless they know exactly what they're doing.

fietsbob

Im familiar with Internally butted steerers .. the fork crown race seat is part of the fork crown.

the part of that , after brazing gets cut with a special tool, made to machine the casting
to allow a decent press fit of the headset crown race.

now as the cutting edge moves past my needs I see there are forks with a much larger bearing on the bottom than the top.

Bearings ..1.5" bottoms , 1,125" tops .. so be it..

Al1943

If it takes a lot of force to hammer the race on don't do that! There is a special tool for facing the crown collar.

FBinNY 

The OP describes a steerer with a crown seat diameter extending up about an inch. This then is not a classic brazed steel fork with a machinable crown seat as part of the crown, but a bulge formed steerer either of steel or carbon (he doesn't specify).

Neither of these are designed to be milled, and should come from the factory within tolerance ---- 5/100ths of a millimeter over the nominal. If it isn't that or close - plus or minus a few 100ths of a millimeter, something is wrong, and his best course of action is to either return the fork, or consult someone familiar with the job.

There's no harm in sanding off a few 100ths of a mm on a steel bulge formed steerer. but it shouldn't be necessary, and IME very rarely is. If in doubt, the first step would be to measure. Remember it's always possible to remove material, but never possible to add back.

Al1943

OK, but my "all carbon" forks have aluminum machinable crown race seats. And one of them had to be milled a bit before the crown race could be seated.

FBinNY 

Yes, raised crown seats separate from the steerer or part of the crown itself are non-structural and machinable - either the factory did it, or end user can. But bulge former steerers don't have the non-structural element, and that's the issue. If you mill, cut, file or sand these, you're removing structural material from the steerer, and depending on the method, may leave tool marks which can become stress risers.

The reference to the 1" length and taper strongly suggest a bulge formed tube, and my advice is based on that. Of course, it could be machinable, but in the absence of sure information about the construction I have to advise the conservative course -- especially as it relates to a fork crown.

LesterOfPuppets

Fietsbobs post has me worried. Could this be a tapered fork with non - tapered hs???

What is frame make model year and fork make model year?

cderalow

This was of course my first thought.

Especially with common all carbon forks these days, a good 90% are tapered.

There's not much of a difference between 1-1/8" and the common 1-1/4" tapered bottom, in fact, it's less than 4mm total diameter difference.

FBinNY 

Admiral Hopper's maxim applies here. the OP needs to measure the fork, and know what he's looking at before doing anything that might be cause for regret.

The OP's original question is whether steerers are in tended to be cut to seat a crown race. My answer, based on the (incomplete) description of his fork was no. It remains so. The possibility (it never occurred to me that someone would consider cutting that much material away) of a tapered steerer only makes it more important to check what he's dealing with.

adlai

https://www.flickr.com/photos/289551...57645785695883

there's a photo of it. It is very slight, but just enough to make it difficult to fit a ring around it.

LesterOfPuppets

Whew, it's not tapered and it's not full carbon.

With the right tool you should be able to hammer the crown race on


You asked about getting a different headset. I'd be tempted.
I love threadless headsets with split ring crown race.

adlai

The split crown race I've tried expands so much trying to get it on that it doesn't fit on the adjoining ring when pushed all the way down.

FBinNY 

OK, that's a machinable ring. I doubt it's anywhere near the 1" height you originally described, but we're long past that.

The job is properly done with a hollow mill, or "crown race mill" which is an expensive shop tool. It can be done with a file, but only in the hands of someone pretty skilled, since you have to maintain concentricity and a flat bottom (critical).

Any decent bike shop can do the job, and I'd expect it to run $15-25.00. I know a number of dealers throughout the country, and if you say where you live, I or someone could probably steer you to the right shop.

hueyhoolihan

i don't see the problem, except that the OP may not understand what a press fit is and how much pressure must be applied to make it work.

FBinNY 

Forks with raised ring crown seats are made oversize, and need to be hollow-milled to size. That may or may not have been done by the maker, and the only way to know is to measure, either with a go-nogo ring gauge made for the job, or with a micrometer or caliper. As I described very early on, the fit tolerance is 0.05mm ±0.02mm over the nominal size.

If the seat is much more than 0.05mm over the nominal, he risks shattering the crown race or if the lip is aluminum broaching it down pushing a burr ahead.

OF course, there are any number of hack or emergency alternatives to doing it right, but the OP has a brand new fork and headset, and might as well do things right.

BTW- why is it that every time I mention the need to measure anything on this forum, folks keep trying to dance around it. Why guess or argue, when a definitive answer is at hand?

LesterOfPuppets

That fork doesn't look very new to me.

Hard telling why people hate measuring. I'm dying to know the diameter myself.

Still curious about make/model/year for frame, fork and headset, too.

adlai

Doesn't look new due to me being an ape trying to install it.

AnkleWork

Why not consider removing material from the race instead of the fork?

AnkleWork

Utopian dreamer.

hueyhoolihan

i think i remember just a few days ago somebody was complaining about not being able to the his or her crown race on, and low and behold it ended up that they were just unaware of what it takes to get one on.