Headset install: Fork crown race - damaged crown shoulder
 

I am not sure how to go about this headset install - see images below. The crown race shoulder is damaged. The quarter of the shoulder is still intact, but the rest is only partially there, and small section is missing completely. The crown race will be held on by mostly the little shoulder left at the bottom - not loose, but I am not sure how long it will last.

I am thinking epoxy for reinforcement. Alternatively, remove the damaged area and insert a shim? Please let me know if you have any other suggestions. Thanks!

The frame is Bridgestone Radac 2000, 1987.

https://cimg5.ibsrv.net/gimg/bikefor...5f30195784.jpg
https://cimg6.ibsrv.net/gimg/bikefor...2ee71b97a0.jpg

Is your crown race 27.0 or 26.4?

Too bad 25.4mm crown races don't seem to have been made.

I'm not a big fan of JB Weld on bikes, but this might be one place I'd make an exception, at least to try it out. Put on the JB weld (clean, loose stuff removed), then cut the fork crown down to 26.4mm. There should be tools to do it.

Thanks for your advice. The crown race is 26.4. I found the cutting tool - CRC-1 - by Parktool, but purchasing this is out of question and will need to improvise.

https://cimg9.ibsrv.net/gimg/bikefor...c12722b3f5.jpg

Take to good mechanic at good bike shop that has the tools.

You can probably shape it by hand. However, it does need to be a good tight fit.

Yes, any bicycle specific reamers and cutters are expensive, but as @trailangel mentioned, a bike shop should be able to help you out. Find a good, little older shop. Explain what you have planned before you start.

https://www.jbweld.com/collections/m...xy-putty-stick

I've also reinforced JB weld with bread tie wire, steel wool, etc.

If this fork was brought in by a customer I would suggest they don't continue to ride it any longer. This is a bonded together AL crown (and blades) to a steel steerer. The crown race "shoulder" has cracked and broken off partially around the steerer. When AL starts to crack wise ones take note:)

Sure one could make a claim that the broken off portion is only supporting the crown race. As in a non structural failure. Still I'd hate to have to say under oath that I knew the fork had cracked yet I felt it was going to be safe after "repairing" using rather unconventional methods.

I do wonder what was the cause of the broken "shoulder". Was it riding with a loose headset? Was it from some impact long before? Was it from poor initial fitting/bonding? Without this backround I don't see how I can suggest using this fork to keep one's face off the pavement.

Your opinion may differ. Andy

How much is a new fork going to cost compared to the amount of time you are going to put into this one?

I agree with Andrew, I would not ride this fork. To me, it appears that the bond of the steerer tube to the crown either was not that good to begin with or just separated. This suggests to me, that the remainder could separate. I'd get a new fork (or bike) depending on what you want to spend.

Hmmm...
Reading about the Lambert/Viscount forks.

Lambert & Viscount bikes: About those Lambert / Viscount Death Forks

The issue they apparently had was that the steel steer tube ended at the top of the crown, and was simply pinned to a fork extension.

The "Type 3" fork had the steer tube that extended through the crown, and the brake bolt went through it.

The OP's fork is probably a different brand, but hopefully has the full length steer tube similar to the later generations of Lambert forks (and many composite forks today).

Whether one wishes to ride it or not would be personal preference. It would be worth reviewing information on forks & bonded joints.

I agree with the above recommendations to consider a replacement. Is the fit of the steerer tube solid? If not, then you should replace without question. If you think the steerer/crown joint is good you will want to examine the crown carefully for any signs of cracking. Be cautious.

To address your initial question about fitting a crown race: Not much you can do but keep what metal is there and use epoxy to fill in.

Plus the possible medical/dental bills if it fails; the potential for catastrophic failure (and I don't perceive any "minor" or "recoverable" failure mode on a fork, you are going down hard) is too great.
People put too much faith in epoxies IMO. JB Weld is NOT as strong as a weld by a huge factor.

I missed the crack or separation. Buy new fork.

I'm not considering JB Weld as a structural component, but rather a limited compression spacer which it should be able to hold up to.

Perhaps one could make a washer/ring that would do the same thing. Cut off all the aluminum, all the way around. Then heat up and press on a brass ring. Get a shop with the seat tool to finish it to size.

There are a few used bonded aluminum forks available.

But, for new forks, is anybody making quality aluminum road forks? Perhaps a couple of aluminum MTB or Cross forks. :foo:

1"? Fewer still.

So, that leaves us with Carbon Fiber. :crash:

...just looking at the pictures, I agree with the "I would not ride that" crowd. You can see a little rust on the steerer where the crown has flaked away. You can't actually see the hidden surfaces of the bond between the two parts, but it's not worth the risks involved when you can buy a pretty decent new fork on Amazon or Ebay for less than a hunnerrt bucks. Your issue is not whether you can form up a seat for the crown race, but what's going on where you can't visualize the surfaces between dissimilar metals..

...I don't think anyone is suggesting an aluminum replacement fork, Clifford. I know I'm not.

Additional images
 

Thanks for your thoughtful comments @Andrew R Stewart. The cause of this issue is unknown as I got this second hand. It was converted to single speed and had non-stock headset which I removed. I thought to it may be fun to rebuild this as (close to) the original spec (so time is no concern here - @Iride01). I have a donor bike with 105 components. The bike was somewhat rough, and there was another damage to the frame: seatpost bolt was tightened from non-driverside.

As far as I can tell, there is no damage to fork crown. The steer tube does go all the way to the bottom of fork crown - @CliffordK. The "shoulder" or seat for crown race is aluminum and appear to be a separate piece inserted into the fork crown but not sure how far it goes down. - like a shim between steel tube and aluminum fork crown.

I cleaned it up for close up images:

https://cimg8.ibsrv.net/gimg/bikefor...b2109d7b82.jpg
https://cimg9.ibsrv.net/gimg/bikefor...fac120d100.jpg
https://cimg0.ibsrv.net/gimg/bikefor...23d68ce79b.jpg

https://www.cyclingforums.com/thread...-fraysse.4612/

...people start threads here all the time about the various aluminum frames of this time period that all shared a similar construction method. Generally, the advice ranges from " a little JB Weld and that will buff up nicely" to "you're gonna hurt yourself and probably die".

It's a problematic frame construction method, that was doubtless never intended to live forever.

It's your bike, and your oral and maxillary facial reconstruction procedure if you guess wrong. While "original" restoration is an admirable goal, sometimes functional modification is a better compromise if you intend to ride something. A chrome finish Tange steel fork would probably not look terribly out of place, and would definitely have a better percentage chance of going the distance. Fork and head tube failures can be catastrophic in nature. Most of us are fortunate enough not to experience them.

Hold on now. First, let's recognize that so-ichiro has a very interesting bike. Grant Peterson designed. I'm not an aluminum bike guy, but the Radac were and are gorgeous.

It seems to me that the fork has a couple issues. The first is that a thin spacer/bushing has worn out. The second is that the bearing face (that is, the top of the crown) has been worn, possibly unevenly. If this were my bike and I had access to a machine shop I'd have the bushing turned off (taking care to take nothing at all from the actual steer tube. Then I'd face the top of the fork crown very lightly, leaving no groove anywhere. At this point, inspect and ask how confident are you that the thing is ok. I mean, it's an Al tube bonded into an Al fork in the first place, right (correct me if I'm wrong)? So if the tube itself is ok, maybe there's hope.

At that point, you might be able to find or fabricate an Al washer and an Al bushing to match the original. Light interference fit (that, you make the hole in the bushing smaller than the tube and use a press or temperature to fit it on). Or a slightly looser fit with epoxy to seat the washer against the fork and the bushing on the tube.

I probably wouldn't use epoxy to make up the bushing.

I'd inspect a bit more before giving up. But remember, your decision, your teeth. I've broken my jaw going over the bars on a bike, and its no fun.

Good luck!

...do you happen to know how the fork crown and steerer are bonded ? If it's an aluminum steerer, I don't know where the rust in the first couple of photos is coming from.

IMO the steerer is steel. The very dark/black edges of the crown/steerer "bond" has me suspect. As in a lack of bonding agent applied, none squeezed out. Of course what I think I see is exactly what really is:) Andy

I appreciate your suggestions @WizardOfBoz. This is clearly beyond my ability though.

@3alarmer, the steerer tube is steel.

I am wondering a bit about the bond.

The Viscount page seemed to indicate heating and shrinking to form a bond, which I would assume precludes using epoxy.

This is a different company, of course, but I wonder if there would be a similar shrink/press bond.

A couple of years ago there was a company that specialized in restoring Vitus frames. Ahhh, I think I found them.

Untitled Document

Anyway, perhaps they would be worth contacting, and might have more specific information about the fork, and perhaps even setup for a repair.

Are you looking at the bottom side of the crown? No obvious glue there, whereas I see some gray glue-ish thing on crown/blade junctions but that is aluminum to aluminum. On top side of the fork crown, some aluminum shoulder piece came off - no glue underneath, but whatever left there is still stuck pretty good.