Crown race doesn't fit tight what am I missing?

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Evanfrucht

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Hey, new to this stuff so forgive me. The crown race I have doesn't fit tight on my head tube and is not sitting perpendicular. I'm also not sure if my head tube is bent sightly foward and sideways, maybe that's why it isn't sitting "flat." Either way it's lose on there. The ID of it the crown race (ive just learned this is the name for the bottom bearing surface) is about 27mm and the OD of the head tube on my old 50's shock master fork is about 25.5. What am I missing?
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I would say that you have the wrong size crown race for that fork.

as to the bent issue, I don't think you can assume that the crown race seating area is 90' to the steerer tube. I would hold your square flat to the tube...slide down to the crown race seat...and then measure the distance from the 'L' to the outboard of the top of each side of the fork and compare.

Jason
 
RustyGold said:
I would say that you have the wrong size crown race for that fork.

as to the bent issue, I don't think you can assume that the crown race seating area is 90' to the steerer tube. I would hold your square flat to the tube...slide down to the crown race seat...and then measure the distance from the 'L' to the outboard of the top of each side of the fork and compare.

Jason
Click to expand...

OK thanks for the input. Im trying to install this old 50's shockmaster fork on my newer Schwinn cruiser that I'm customizing. The bike came with a reproduction schwinn style springer and I had hoped to just transfer all the head tube hardware over. It seems likes it will work but I can not get the crown race to sit right so that the lower bearings will make proper contact with the bottom of the headtube. Both of the the fork tube have the same OD 25.4 mm (or 1 inch.) The thing is... the crown race only work's on the repro schwinn fork tube because the bottom 1/4 where the crown race sits is machined to a bigger bore in order to fit the crown race very snug. On my 50's shockmaster that is not the case.

I'm trying to figure out how I can make this work properly. Am I missing a special piece of the fork?

I googled 25.4 mm crown race hoping I would find one that would fit tight on it's own but got no results.

Any ideas.

Who's got one of these ?

Also the square was just meant to show the directions of the bend I don't have it held up very precisely
 
The Renaissance Man said:
I agree, wrong size race.
The steer tube does look bent in the photos even without the square. That's not uncommon with old forks though, many years of abuse!
Click to expand...

Do you know where can I get the correct size race or a spacer/shim of some sort ?

Also any ideas for straightening this fork?

Also would be nice to strengthen/reinforce it as I plan to ride this bike hard, any ideas ?
 
I would assume your going to have to chase down a CWC crown race. You need to be sure the bearing size/cage size matches the lower cup you are using as well. Other possibility is have a machinist make one for you...but, that will be bucks. There are 25.4mm to 26.4mm (standard iso crown race I.D. size) seat post shim, but, I can only imagine it would be a pain to cut down and get in there...but, maybe not.
https://www.bmxguru.com/products/seatpost-shim-25-4-to-26-4-seat-post-1-0mm

Any straightening of the current steerer is going to result in weaker than it was new (though probably fine for normal riding). Replacing the steerer tube (cutting off, and welding in a new one) is probably the only route to have it as strong, or stronger than, new.

I don't know what you mean by 'ride hard'...if you mean klunking, you probably have the wrong fork for the job. If you mean, lots of miles...then, I would probably just straighten...check for cracks...and use it. :grin:

Jason
 
From my summer experience with my 1912 Iver Johnson, I'd rather replace the steerer than straighten it just for the piece of mind and it's much cheaper than replacement teeth.
 
RustyGold said:
I would assume your going to have to chase down a CWC crown race. You need to be sure the bearing size/cage size matches the lower cup you are using as well. Other possibility is have a machinist make one for you...but, that will be bucks. There are 25.4mm to 26.4mm (standard iso crown race I.D. size) seat post shim, but, I can only imagine it would be a pain to cut down and get in there...but, maybe not.
https://www.bmxguru.com/products/seatpost-shim-25-4-to-26-4-seat-post-1-0mm

Any straightening of the current steerer is going to result in weaker than it was new (though probably fine for normal riding). Replacing the steerer tube (cutting off, and welding in a new one) is probably the only route to have it as strong, or stronger than, new.

I don't know what you mean by 'ride hard'...if you mean klunking, you probably have the wrong fork for the job. If you mean, lots of miles...then, I would probably just straighten...check for cracks...and use it. :grin:

Jason
Click to expand...
By ride hard I mean I'm shoving a motor in there, HA! Speeds of 20-30 going over small bumps/road imperfections. It's probably fine as is, its seems strong enough and made of cast iron... and who knows how it got slightly bent originally.

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More weight plus higher speeds...I'm kind of with duchess on the replacement of the steerer. An in between fix would be to straighten it, (check for cracks), and then press in another length of tubing to reinforce. That would also probably take a machinist since I would be shocked if the ID of the steerer was a common size.

Jason
 
I would probably just set out to replace the forl tube but I'm not sure I'd be able to weld a steel pipe to the cast iron fork. I have a mig welder with mixed gas. I generally don't mind that kind of project... I could probably get the correct sized tube and thread it easily enough. Just don't know about welding and on top of that how would I even jig it up to make sure the new one was perfectly straight?

Anyone ever replace a head tube on a cast iron fork like this?

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I don't particularly know anything about the shockmaster forks...but in your pic, it doesn't look cast...it looks stamped from plate.

Jason

edit...I just did a search and I've seen several other claims that they are cast, so I guess they are :bigsmile:.
 
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RustyGold said:
...it still looks like stamped plate in your pictures, to me. I'm going to have to really eyeball the next one I run across :nod:.

Jason
Click to expand...
To be honest I don't know what it is for sure and I'm not sure off the top of my head how I could easily distinguish the two materials.

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Cast steel and low carbon forged/rolled steel is the same composition...so, the only way to tell is going to be visually. If cast, there should be a thin casting line somewhere...if a forged part, a thicker line, probably ground down...if stamped from sheet ???

The reason I think stamped, is that some of the edges look sheared or torch cut, but mostly, the inside corners on your second pic look to be formed by bending...not forged or casting, given the distortion in the bends. The bottom side of the fork, opposite the steerer tube boss, would probably be the biggest clue. If it has an indent matching the boss...I would guess it is stamped plate.

Jason
 
RustyGold said:
Cast steel and low carbon forged/rolled steel is the same composition...so, the only way to tell is going to be visually. If cast, there should be a thin casting line somewhere...if a forged part, a thicker line, probably ground down...if stamped from sheet ???

The reason I think stamped, is that some of the edges look sheared or torch cut, but mostly, the inside corners on your second pic look to be formed by bending...not forged or casting, given the distortion in the bends. The bottom side of the fork, opposite the steerer tube boss, would probably be the biggest clue. If it has an indent matching the boss...I would guess it is stamped plate.

Jason
Click to expand...
Ya you may be right. I really don't know and honestly just assumed it was cast iron for some reason. I'll post some more pics of the underside tmrw.

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You want to do Spark testing ito determine the type of ferrous material.
A bench grinder is usually used to create the sparks, but sometimes this is not convenient, so a portable grinder is used. In either case, the grinding wheel must have adequate surface velocity, at least 23 m/s (4500 surface feet per minute (sfpm)), but should be between 38 and 58 m/s (7500–11,500 sfpm). The wheel should be coarse and hard, therefore aluminium oxide or carborundum often are employed. The test area should be in an area where there is no bright light shining directly into the observer's eyes. Moreover, the grinding wheel and surrounding area should be dark so that the sparks can be observed clearly. The test sample is then touched lightly to the grinding wheel to produce the sparks.
Spark_testing_2.png


(A) Wrought iron (B) Mild steel (C) Steel with 0.5 to 0.85% carbon (D) High-carbon tool steel (E) High-speed steel (F) Manganese steel (G) Mushet steel (H) Special magnet steel

The important spark characteristics are color, volume, nature of the spark, and length. Note that the length is dependent on the amount of pressure applied to the grinding wheel, so this can be a poor comparison tool if the pressure is not exactly the same for the samples. Also, the grinding wheel must be dressed frequently to remove metallic build-up.

https://en.wikipedia.org/wiki/Spark_testing
 
I have several of these forks. They are stamped.
Look at the headlight mount, it is twisted 90 deg. so that the hole is positioned horizontally. They would not twist a cast piece.

That being said, I would still be curious how one would replace the tube and keep it square and plumb.
 
It will not do much good to replace the steer tube, if the junction with the fork crown (stamped area) is bent. I would make a square that allows you to judge the angle from the fork crown instead of the race area. If this is bent sideways, it may be impossible to bend back without a hydraulic press.
 
cman said:
It will not do much good to replace the steer tube, if the junction with the fork crown (stamped area) is bent. I would make a square that allows you to judge the angle from the fork crown instead of the race area. If this is bent sideways, it may be impossible to bend back without a hydraulic press.
Click to expand...
I think it's the actual tube that is bent slightly near the base.

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And yes I now see it is stamped steel. I bought at a swap meet and first impression was that it was cast iron. Went home did research and saw someone label it as cast iron too. Didn't really do much investigating or think about it much. I'll let you guys know how it turns out.

It doesn't need to be perfect honestly.

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