# Monark fork bearing cup shims



## mrg (Sep 4, 2018)

(Though Id bump this, I've made a shim bit still looking for a OG one ) Trying to get my loose fork bearing cup problem figured out, missing OG shims ( think Monark Speedster & 5 bar only ?), made some but still don't know if they are right (fork comes loose after short ride), I guess there is a thin and thick ones, I think I need the thin ones, the pic is a thick one I think,


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## Freqman1 (Sep 4, 2018)

Mark that pic looks like the correct ones. I think the key is getting the right thickness sheet metal for the shim. The cups should fit snug in the head tube with no play. V/r Shawn


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## kunzog (Sep 4, 2018)

I use shims that I cut out of beer or soda cans


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## WetDogGraphix (Sep 4, 2018)

Like this?    I've got 4 different thicknesses of brass.....I could cut and send you some to try......This size fit's my Twin Bar....


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## FSH (Sep 4, 2018)

I have laminated shim stock.  What thickness?  Mine are about .030 with .002 laminations


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## SKPC (Sep 6, 2018)

I would 1st have your head tube openings re-surfaced(shaved) to be parallel to each other by a good bike shop.   These old frames tend to have out-of-round head tubes that over the years may stretch out because of hard use or big hits on forks.  If you use a shim like above, make sure the shims do not keep the headset cups from seating cleanly on the frames' head tube openings. This keeps all the bearings cleanly contacting the cups' and cones' races.


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## mrg (Sep 6, 2018)

Well the shem helped but noticed the frame is worn (probably from no shims & excessive use) on top/back making the cup sit at a angle, never thought about shaving it off, I was going to add some material (a weld then grind flush) to make it flush with frame and parallel with bottom cup, as far as shem thickness i don't know, I may have to take some of you up on your offers but still would like to find some OG, I like WDG's with a lip to keep the from sliding into the frame, do the cup still seat all the way in the frame?


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## JAF/CO (Sep 6, 2018)

mrg said:


> Well the shem helped but noticed the frame is worn (probably from no shims & excessive use) on top/back making the cup sit at a angle, never thought about shaving it off, I was going to add some material (a weld then grind flush)View attachment 864734




Strip of a ten can rap to fit


James Frazier (209) 481-9464
jfkiller53@aol.com


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## buickmike (Sep 6, 2018)

Thought I could do better?
Actually one side is more worn than the other. The pop can on one side - maybe brass shim on other.As far as the lip that's only way I've ever done


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## Freqman1 (Sep 6, 2018)

Once you fix the worn head tube the tin can shims will work fine. The head cups will not seat all the way if you put a lip on it. V/r Shawn


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## SKPC (Sep 7, 2018)

^^^^^^ See above comment....1st things 1st.   Look closely at your last pic of the head tube. The bearing cone is not parallel with the headset cup!  Looks to be 1/8" higher in the front, which means the head tube is very damaged and out-of-true.  This will cause even more damage if you run it like this. 
      For the frames' wellbeing and to solve the problem once and for all, get the top and bottom of the head tube professionally "shaved".  A special tool is required to do this. Any bike shop should have one.  Slapping a weld and hitting it with a grinder will not cut it.  What does the bottom of the head tube look like?....


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## mrg (Sep 7, 2018)

I hate to loose metal (shave) so was going to add materal (weld) to the back of the top bearing cup seat then grind flush and parallel with the bottom.


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## Freqman1 (Sep 7, 2018)

I agree with you Mark a shave on something like this is probably not a good idea. I’d see about adding the metal and get with a good machinist to make it right again. V/r Shawn


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## buickmike (Sep 7, 2018)

I have yet to see a local bike shop that would be so well equipped. And willing to help a customer out. At least this customer. The original posters bike is pretty weathered
I would have difficulty locating new cups for the head tube as most of my stuff is Schwinn.


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## SKPC (Sep 7, 2018)

mrg said:


> I hate to loose metal (shave) so was going to add materal (weld) to the back of the top bearing cup seat then grind flush and parallel with the bottom.




That _is_ the best option since the paint is shot, but it still will require some tool-age and maybe shims also.  If you go that far, machine or "shave" it so the  headset goes in tight, flush_ and_ parallel w/o shims..


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## buickmike (Sep 7, 2018)

Anyway here is second attempt at THICKER shim for colson BB.Would be nice if people would let me pick thru the stores old inventory - but they dont- so I buy what they have which was generic bmx cups etc.
Final fit on non sprocket side was both aluminum + brass sham combo. AND whacked my fingertip 2


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## Freqman1 (Sep 7, 2018)

These came from the factory with shims. I have not seen a cup/bearing set that will work in this head tube. But hey what do I know about these bikes. V/r Shawn


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## SKPC (Sep 7, 2018)

Maybe clear this problem up by keeping the shims out of the equation & put normal cups in it. Poor design imo.


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## mrg (Sep 7, 2018)

They are normal cups ! ,  when Monark designed the Super frame (5 bar), Speedster (twinbar) and others (?) they were really different (revolutionary) including head tube stock and not wanting to make special hardware (fork bearing cups) that were usually purchased from hardware supplier, they just shimmed them to fit the frames. After years of ware (abuse) and probably disassembly many times the shims were either worn out or lost. the further use and or abuse caused top cup to move and ware the frame. when I got it the springer was not even assembled correctly and did not even function as a springer ( how many times did you take apart your bike when you were 10), so it's not a issue of finding right cups, its repairing the ware on the frame and finding OG shims or making them. I almost just made a shim with a lip o the back to level the cup but might as well do it right. with me it won't be machining/custom fab etc., just weld a bead over the worn spot to add material then grind/file and a use a square/ruler to make it even and parallel & back to OG and needing shims like when it left the factory. this ain't rocket science and don't think I'll be running Baja 1000 with it an I built cars for that without much more.


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## SKPC (Sep 8, 2018)

Great idea mrg….nice frame to begin with and worth getting fixed up! Love that bike..skpc


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## mrg (Sep 8, 2018)

Ya, probably poor design on the whole frame, only a few survived, I have only seen 3 or 4 in 35 yrs. 3 owned by Cabers and 1 in the Evolution book , breaks & welds in other places on 1 or 2 of the others. the shims are FACTORY for this model so it takes normal cup with a shim and I want it OG so with shim, somebody probably took out the shim years ago and that's what started the ware problems.


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## Kickstand3 (Sep 11, 2018)

WetDogGraphix said:


> Like this? I've got 4 different thicknesses of brass.....I could cut and send you some to try......This size fit's my Twin Bar....
> View attachment 863773




I would take Wet Dog up on his offer sounds like he’s got experience with this issue. Thanks for posting this Mark Iv got a few of these bikes waiting to get serviced.


Sent from my iPhone using Tapatalk Pro


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## rustjunkie (Sep 11, 2018)

This:






https://www.parktool.com/blog/repair-help/head-tube-reaming-and-facing

this:





then this:


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## kreika (Sep 11, 2018)

@FSH


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## FSH (Sep 11, 2018)

kreika said:


> @FSH



The only thing I would replace is the solid shimstock.  This should be laminated so that you can peel away the material until you get a good fit.  I believe I can make some with a flange.  Anyway my 2¢


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## WetDogGraphix (Sep 11, 2018)

When I hear layers, this is what I think..these came out of the head tube......




I have several thicknesses of brass and ended up using .016". It now has a 1/32" lip.




The fit was perfect, didn't slip right in, but also didn't have to pound it in. This worked for me.



Whatever you decide to do, good luck.  I'm more than happy to send you some strips to test......I bought a lot for my 2 shims.....


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## FSH (Sep 11, 2018)

This is what I mean...


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## WetDogGraphix (Sep 11, 2018)

FSH said:


> This is what I mean...View attachment 867492



Not sure what that is, or how thick that is, but some other info is needed as to what you are showing. In other words, the thickness, the flexibility of it, etc. Interesting concept.......


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## FSH (Jul 14, 2020)

I make these shims for South Bend lathes.  I think that I can *roll* a shim with a flange that is made out of the same material.  The full thickness of the material is .032 with laminations that are .002 thick.  Essentially the shims are glued together and peelable.  The Idea is that you would get a one-size fits all shim.


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## mrg (Sep 28, 2020)

I don't know the thickness's, that's why I'd like to just find the OG ones.


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## zedsn (Oct 21, 2020)

I have a bunch of bearing cups. Can you digitally measure the thickness that you need and I will see if I have one that would work for you.


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## mrg (Oct 21, 2020)

Thanks anyway, I have the OG bearing cups but some Monark's needed a shim to fit some frames especially the 5 bar & twin bar/speedster. 2 yrs and haven't found og shims, anyone parting out a old girls 4 bar with shims?


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## Superman1984 (Oct 27, 2020)

mrg said:


> Thanks anyway, I have the OG bearing cups but some Monark's needed a shim to fit some frames especially the 5 bar & twin bar/speedster. 2 yrs and haven't found og shims, anyone parting out a old girls 4 bar with shims?



Why not put a piece of pipe that fits snug around the cups that fits the frame tube tight & forget the shims? I mean ultimately you can grind & file it to fit tight. Using worn shims from another bike of the same design will ultimately yield the same problem if your actual head tube & frame are worn that badly


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## mrg (Oct 27, 2020)

I have made shims and they work fine for now. most of the time it's not that they are worn out it's people ( kids ) just didn't bother to put them back in and that's where the excess wear on the frame comes in, from no shims so would still would like to find a OG set to put in and never have to worry about it again, I will never put enough miles or abuse on them to where them out.


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