# What is going on here?



## ballooney (Dec 17, 2017)

Bike: '49 B6 

Problem:  crank arm will not clear the chain guard. 

Outer Measurements between chain stays taken at the drop out (5") and just after the kickstand housing (4 1/4") are the same as another B6. So there doesn't appear to be a bend in the frame after the bottom bracket. 

Crank that came on the bike appeared bent so I replaced it with the crank that works fine on another B6.  Here is the crank that came on the bike...looks to be a 1" flare when using two straight edges:





Here is a crank that is straight for comparison. Looks to have a 3/4" flare:




With a straight crank on the bike in question, here are my clearances:







Compared to a B6 with no issues:







The B6 with the clearance issue seems shifted in that there is plenty of clearance on the non-drive side but almost no clearance in the drive side. Just the opposite of the good B6. 

What got me here?  The bike rode oddly under feet like a bent shaft on a pedal. So I started pulling it apart...pedal shaft was straight. Pulled the crank and noticed it was bent...ah ha!  Picked up a straight crank and boom, clearance issues. Must be a bent frame in which the original crank was bent out to accommodate the clearance issue but the measurements on the chain stats match a good bike. So what gives?


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## rollfaster (Dec 17, 2017)

maybe the triangle is out of alignment? Had the same issue with a 48 DX.


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## rollfaster (Dec 17, 2017)

https://thecabe.com/forum/threads/schwinn-crank-issue-for-dx.80643/


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## ballooney (Dec 17, 2017)

rollfaster said:


> https://thecabe.com/forum/threads/schwinn-crank-issue-for-dx.80643/




What did you end up doing to resolve your issue?


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## Two Wheeler (Dec 17, 2017)

Install your peddles. If the crank arm/arms are bent you should be able to tell by the angle of the peddles. Is it the original chain guard? Maybe the chain guard is tweaked? Try moving the guard as far forward as possible. If that doesn't work, try going aft. Position it where the interference is the least. Then gently persuade the guard away from the arm.


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## rollfaster (Dec 17, 2017)

ballooney said:


> What did you end up doing to resolve your issue?
> 
> 
> Sent from my iPhone using Tapatalk



Sure did. I was able to correct it by doing the 2x4 trick. Somewhere there’s a thread on re-aligning the rear triangle. Mine was out of alignment on the drive side causing the crank arm to hit the frame. I’ll see if I can find the thread.


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## ballooney (Dec 17, 2017)

String test shows rear triangle to be evenly spaced in relation to the seat tube...if I did this correctly?














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## Two Wheeler (Dec 17, 2017)

Here are a few pictures of my 48 DX. As you can see there is not much clearance between the crank arm and the chainguard. How hard is your crank hitting your guard?


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## Two Wheeler (Dec 17, 2017)

One more picture.


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## ballooney (Dec 17, 2017)

Dan Shabel said:


> Here are a few pictures of my 48 DX. As you can see there is not much clearance between the crank arm and the chainguard. How hard is your crank hitting your guard?




The crank is completely blocked by the guard.


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## buickmike (Dec 17, 2017)

Id like to add .   The chainguard can be mounted in inside of frametab or outside. Depending on clearance requirements.. I thought I saw maybe fender didn't have relief for chainguard to tuck in. Been a long time since I built this 48. Barely clearing on non drive side. The bearing cone - all diff size so I had to choose a good 1 And cups were worn etc. I hope you have plenty of spare parts for this build.


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## GTs58 (Dec 17, 2017)

The 48 catalog shows the guard mounted on the inside of the mounting tab.


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## SJ_BIKER (Dec 17, 2017)

What hardware are you using....


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## SJ_BIKER (Dec 17, 2017)

Theres a jig to check the trueness of the frame


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## SJ_BIKER (Dec 17, 2017)

One photo shows the front tube angled at a odd angle....


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## ballooney (Dec 17, 2017)

Dan Shabel said:


> Install your peddles. If the crank arm/arms are bent you should be able to tell by the angle of the peddles. Is it the original chain guard? Maybe the chain guard is tweaked? Try moving the guard as far forward as possible. If that doesn't work, try going aft. Position it where the interference is the least. Then gently persuade the guard away from the arm.




Thanks for your input.  The chain guard is original.  I have mounted the guard on the inside of mounting tab and outside...no luck with clearance.


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## ballooney (Dec 17, 2017)

buickmike said:


> i.d. like to add .   The chainguard can be mounted in inside of frametab or outside. Depending on clearance requirements.. I thought I saw maybe fender didn't have relief for chainguard to tuck in. Been a long time since I built this 48. Barely clearing on non drive side. The bearing cone - all diff size so I had to choose a good 1 And cups were worn etc. I hope you have plenty of spare parts for this build.
> 
> View attachment 726079
> 
> ...




I have just the opposite for clearances...plenty of clearance on the non-drive side but barely clears on the drive side.  Yet, with the string test, the rear triangle appears true.  Strange.


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## ballooney (Dec 17, 2017)

SJ_BIKER said:


> Theres a jig to check the trueness of the frame



I used a string from rear-drop outs, around head tube and back around.  Measuring seat tube to string appears to be the same for both sides concluding the rear triangle is in alignment.  Could the bottom bracket be off?  Puzzling!


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## buickmike (Dec 17, 2017)

Just looked at pic showing "straight. crank in frame. .Definitely too many threads exposed on non sprocket side. So lets move it (crank)  over with intent of clearing frame. When I work on bikes lately I'm limited to parts that are usable. Schwinn stuff is common but older parts from 10 spd.   would work? What I would look for are adj. Cones of diff. Thicknesses. All I have left now are repro anniversary BB cups. threw all worn out cups+cones away. Looking at BB on mine you see thicker cups.


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## ballooney (Dec 17, 2017)

buickmike said:


> Just looked at pic showing "straight. crank in frame. .Definitely too many threads exposed on non sprocket side. So lets move it (crank)  over with intent of clearing frame. When I work on bikes lately I'm limited to parts that are usable. Schwinn stuff is common but older parts from 10 spd.   would work? What I would look for are adj. Cones of diff. Thicknesses. All I have left now are repro anniversary BB cups. threw all worn out cups+cones away. Looking at BB on mine you see thicker cups.




Great suggestions. I’ll check the cups and compare with another B6 and try to work the crank threads over giving more clearance on the drive side.  I will also expirement with mounting the guard on different sides of the mounting bracket one more time.


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## buickmike (Dec 17, 2017)

Goodnight then. I might get another 1/16 out of th.  Is     but     its OK and cran. k doesn't wobble this pic and other not only shows crank is square with frame but that rear fender is not fitting. Good luck


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## ballooney (Dec 20, 2017)

Problem solved but it wasn't quite what I thought it would be.  After the frame was proven to be in alignment, I ended up pulling the crank off another B6 and installed to see if there was more clearance...yes there was and it cleared the chain guard too!  Sweet. What was different about this crank?  I noticed the crank in question was missing this washer:




Problem solved right?  I found another washer, installed it and...crank still didn't clear the chain guard. What?  This is strange...I pulled the chainring off of both cranks to compare the good to the bad. Here is the good crank against a straight edge. I marked around the crank keg with pencil onto the bench top for reference. 




Next was the second crank that didn't clear the chain guard (zoom in and you will see the outline of the good crank



It turns out that this crank was bent too?  That seems improbable so I dig up a third crank and it doesn't match the good crank either:




I pull out a 4th crank and ding ding...I found a winner. It had the same profile as the good crank. 


 
And it clears the guard...yay!!!!




So what's the story? Did two bent cranks send me down a rabbit hole?  Seems like it. Are the cranks used on B6 different than other post war models? 


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## GTs58 (Dec 20, 2017)

Glad you got it all figured out. The crank that's bent looks like the bend starts at the beginning of drive side threading. How does someone bend a crank like that?
My middleweight cranks look to be identical to those other than the cast markings.


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## mongeese (Dec 20, 2017)

Would a washer before tightening lock nut to the sprocket shift the cranks just enough ?


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## Oilit (Dec 21, 2017)

ballooney said:


> Problem solved but it wasn't quite what I thought it would be.  After the frame was proven to be in alignment, I ended up pulling the crank off another B6 and installed to see if there was more clearance...yes there was and it cleared the chain guard too!  Sweet. What was different about this crank?  I noticed the crank in question was missing this washer:
> View attachment 727390
> 
> Problem solved right?  I found another washer, installed it and...crank still didn't clear the chain guard. What?  This is strange...I pulled the chainring off of both cranks to compare the good to the bad. Here is the good crank against a straight edge. I marked around the crank keg with pencil onto the bench top for reference.
> ...



Great information! Thanks for posting!


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