hythamfekry

Hii ,
please refer to pics above, i'm building my new carbon bike, when i insert crown race on the fork , it looks it need decent amount of force to push it into place , i'm just afraid this can cause any marks on the fork fibers or affect its integrity .
i assume this is because on the base of the steerer tube , there's like extras from manufacturing process or something "see first pic"
please advise

Litespud

If the crown race is a really tight fit, you can do a few things:

Use heat/cold - chill the fork (if you can fit it into a freezer) and heat the race - 200F won't damage anything, and see if the hot race will go easier onto the cold fork. Be quick - the race won't stay hot for long.

Use some emery cloth or a rolled up sheet of sandpaper to increase the interior diameter of the race (I personally wouldn't attempt to sand the fork, but others may differ here). This will likely be a slow process.

If the "race" is merely the support for the actual bearing (i.e., the bearing is a self-contained unit - the actual terminology escapes me), then use a Dremel or saw to cut a slot in the race. It's go right on and still do its job of supporting the bearing.
However, you go about it, I wouldn't be too concerned about scuffing up the surface of the carbon, as long as you're not digging into fibers themselves

When I installed a King race on a carbon fork recently, I used a metal tube of suitable width (the handle extension of a floor jack, IIRC) which fit over the steerer, and a white PVC pipe slip coupler, which slid over the pipe, but which contained an inner lip to prevent the pipe from pushing all the way through. The coupler was the right diameter to sit on the race, and the plastic was less likely to mar the race during installation. I rounded off the edge of a short piece of 2x6, so that the rounded edge conformed well with the "crotch" of the fork, placed the 2x6 between two trestles and sat the fork down onto the 2x6. Dropped the race on, slid the pipe/coupler over the steerer and a few robust "taps" with a lump hammer later, the race was firmly set.
The coupler is now irreversibly jammed onto the end of the jack handle, but I how have a "go-to" crown race installer

AnkleWork

Maybe measure carefully before proceeding.

hythamfekry

Don't get your point the crown is the right size , but as u can see in the pic , the very bottom of the steerer tube is a little bit thicker

fietsbob

So, what is the different diameters of that CF steering tube? obviously larger at the bottom than the upper, but by how much?

Perhaps you need a cartridge bearing headset crown race that is split.. being a cartridge bearing the real bearing race is within the lower bearing cartridge

the conic ring on the fork, engages the inner ring of the bottom bearing (integrated headset frame?)







.....

DaveSSS 

I would use emery cloth or a narrow strip of sandpaper and the shoe shine stroke to remove excess material from the crown race area of the steering tube. The manufacturer did a lousy job in that area. The top of the fork crown also needs to be flat. Might need a few care strokes with a file to do that.

A hack saw cut would create a split crown race. Just be sure to scrape off the burrs left by the saw cut.

AnkleWork

How much thicker?

hythamfekry

1 mm or so ..

hythamfekry

crown that cam with headset have proper size , it's just the bottom of the fork steerer have extra traces of carbon molding or something

hythamfekry

hythamfekry

OK , so the options that may work in this case is to use sand paper on the fork or the crown race or cut the crown race and final option is to push the crown race little bit harder so it's snug in place ..
appreciate if you have further comments on which solution is best here ..

TimothyH

It isn't correct to file, sand or cut the steerer or crown race. That is not the way it should be done.

The crown race is an interference fit (press fit, friction fit). The outside diameter of the steerer is supposed to be slightly larger than the inside diameter of the crown race and is not supposed to slip on easily. It is supposed to be pressed on to the steerer. As a matter of practicality, most home mechanics pound it on rather than press it.

I made a tool out of PVC pipe as shown below. A few hits on the the ground and it went right on. All this assumes that it is the right size. If the crown race doesn't install with a few hits on the tool then it is likely the wrong size.

This photo shows that the steerer is larger than the crown race. It won't slip on...




This is the tool. A dremels was used to approximate the shape of the crown race.



Tap the bottom of the tool and the crown race goes on. A few raps and done. If it doesn't go on then measure and confirm the correct parts.




-Tim-

hythamfekry

Thanks for the reply , i expected it should be a press fit , but i was afraid to cause a groove on the carbon or something , alot of people highlighted that for instance using extra torque when installing stem on carbon fork can cause grooves on it , plus that extra carbon molding traces from manufacturing "red arrow" made me thought it's preventing crown race of fitting easily .. maybe will try using few gentle strokes with a proper tool and see if it snug in place

TimothyH

Yeah, a few good raps on the ground and it will eventually seat itself.

I think the PVC cost like $5. I was standing in the plumbing aisle in Home Depot slipping pieces of PVC pipe onto a Niner carbon fork and guys were looking at me like WTF?

Let me know if you are in or near Atlanta.


-Tim-

Kimmo

Wrap a finger around the base of the steerer and turn the fork. Despite the messy appearance, it should feel smooth and uniform.

I hope you're way off when you say the steerer is a whole mm bigger than the crown race; that would indicate you have the wrong headset. 0.1mm is a very tight interference fit; it's usually less than half that.

If you don't have a vernier caliper, spend the ten bucks.

hythamfekry

No , i don't live in the US actually .. i'm on the other side of the globe

hythamfekry

umm . headset and fork are both 1 1/8 .. as in pic , crown race go all the way in except for the last few centimeters . when i touch the base of the fork , it have little high area on the side "some residual carbon from manufacturing" , you may refer to the pic with the red arrow whih shows that ,

Nessism

It might be a good idea to find a shop or framebuilder with a fork crown cutting tool to clean up and/or verify the fork has the proper dimensions.

TimothyH

The fork is carbon. Cutting it will ruin it.


-Tim-

Nessism

Since when? All that's needed is to skim the epoxy layer on the top. I've done this a number of times before without incident.

TimothyH

Maybe I'm misunderstanding.

Are we talking about cutting crown race seats on carbon forks with a crown race seat mill to reduce the diameter of the seat? Or removing excess epoxy, what would be called "casting slag" on a cast product?

I guess the very idea of excess epoxy doesn't sit well with me, let alone having to remove it. The forks I have used have been very clean at the crown race seat. There was no excess epoxy.

My point is that cutting the crown race seat on a carbon fork to reduce the diameter isn't something that is normally done and I doubt any manufacturer would recommend it or warranty the product after.


-Tim-

fietsbob

It's Your face , You go down on, if the fork fails ,

if you consult a Pro Bike shop, before, they will cost less than the Emergency room MD , you may need after..

Nessism

Okay Tim, so let me ask then what you would do with the OP's fork? Pound on the race over the steerer tube inconsistencies shown in the photo? Personally, I'd use a fork crown cutting tool to check the diameter and to dress it up, assuming it's not cutting too deep. If the cutter was showing more than just a light skimming over some of the lumps is needed, I'd stop.

BTW, I clean up the crown race on a NOS Reynolds Ouzo Pro last weeking using a lathe. All that was needed was a very light cut.

TimothyH

Given the fork pictured, I'd probably do exactly as you suggest in bold above.

I wasn't trying to challenge, just understand, that's all.


-Tim-

timsmcm

No cutting needed there. Take a full sheet of wet dry sand paper cut a 3/4 inch strip across the top of the whole sheet and use the shoe shine movement to sand the casting flaws. Then after you have it close take thin super glue and seal up the sanded area. Use a small flat thin paint brush from a hobby store. Put it on thin. After it dries use 600 grit or 800 grit wet dry sand paper to smooth and shine. Clean and smooth as a babies buttox.