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Bottom Bracket Dilemma

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Old 11-04-12, 05:01 PM
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smontanaro 
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Bottom Bracket Dilemma

I have finally collected the various bits I need to build my late 70s Medici frame, but find myself with two Italian threaded bottom brackets, neither of which seem to fit properly. Hopefully, I'm just doing something wrong and someone here can steer me in the right direction.

I have an Ofmega bottom bracket I pulled from an early 80s Bianchi. I had my LBS swap it from one frame to the other. When I retrieved it, the mechanic showed me that on the left side, the bevels on the spindle didn't stick out very far from the cup, and to be careful when installing a crank arm that it didn't hit the cup. I left it as it sat because I had other parts to acquire.

While I was acquiring said parts, I came across a Sugino MT-70 bottom bracket and also purchased the necessary wrenches to service the bottom bracket. I tried installing the Sugino bb today, and find myself with the same dilemma. See the two attached pix (apologies for the crappy cell phone shots and the dirt):



These pictures are of the Sugino bb. The clearances with the Ofmega installed are essentially the same. Looks good on the right, not so much on the left. When I measured the two bottom bracket shells, the Bianchi's was about 69.25mm vs the Medici's about 70.25mm. I can't imagine that shaving a fraction of a millimeter from the shell to get it exactly to 70mm will improve matters significantly, and don't believe I should have to shave off a full millimeter. I believe I have the spindle installed correctly (long side to the right).

What are my options? Find a longer spindle? Find thinner cups?

Thx,

Skip
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Old 11-04-12, 05:14 PM
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How do the arms fit? Is there enough clearance that they don't hit the frame? If so, no worries.

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Old 11-04-12, 05:17 PM
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Skip- Shaving the BB face won't change the distance between the axle's bearing points, therefore any BB that has adjustable bearing design (like the Sugino) will have the same amount of cup to axle end length. Only the amount of cup engagement in the shell would change.

Next question is whether the axle is meant to be used with the crank arms. Some arms and axles (Campy) have a slightly less width to their tapering flats. The other kind (most every Asian brand) of cranks arms will pull further up on the smaller axle.

The next step is usually try to figure out how much more axle length will do the job and try to source said longer axle. Andy.
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Old 11-04-12, 06:29 PM
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Skip the Ofmega unless you are using the Ofmega cranks. The '80s Ofmegas had a unique taper so a shimano or Campi crank won't sit on it correctly.

What crank set are you using? Your kind of doing this backwards, as you need to have the bottom bracket (especially the spindle) that goes with your crank. Different cranks, and event he same crank of different years need a different spindle.

CampI Super/Nuovo Record cranks need a spindle about 118mm long that has a longer section on the drive side. A late '80s Chorus spindle is only about 112mm but symetrical. Same for shimano, SR, Sugino ect.
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Old 11-04-12, 06:45 PM
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Originally Posted by JohnDThompson View Post
How do the arms fit? Is there enough clearance that they don't hit the frame? If so, no worries.
The right side is fine. The left side doesn't hit the shell, but there is nowhere near the clearance shown in your picture.

Originally Posted by Andrew R Stewart View Post
Skip- Shaving the BB face won't change the distance between the axle's bearing points, therefore any BB that has adjustable bearing design (like the Sugino) will have the same amount of cup to axle end length. Only the amount of cup engagement in the shell would change.

Next question is whether the axle is meant to be used with the crank arms. Some arms and axles (Campy) have a slightly less width to their tapering flats. The other kind (most every Asian brand) of cranks arms will pull further up on the smaller axle.

The next step is usually try to figure out how much more axle length will do the job and try to source said longer axle. Andy.
I guess I should have thought about the bb shell width. Makes perfect sense.

The crank is a Campy NR crank from the donor Bianchi. I guess if it's this tight on the Medici it would have been just as tight on the Bianchi. I don't remember looking before tearing it down though.

Here's a picture of both spindles. The Sugino is 119mm, the Ofmega is 115mm.


I'll try assembling it completely (Sugino BB + Campy crank) tomorrow and see what that looks like.
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Old 11-04-12, 06:51 PM
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Originally Posted by Bianchigirll View Post
CampI Super/Nuovo Record cranks need a spindle about 118mm long that has a longer section on the drive side. A late '80s Chorus spindle is only about 112mm but symetrical. Same for shimano, SR, Sugino ect.
Hmmm... The Sugino I have is about 119mm and is asymmetrical.
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Old 11-04-12, 07:46 PM
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Okay, loose ball BB course. #1 bottom bracket spindle lengths are crank specific; A Campy Victory uses a 109mm axle and an almost identical Triomphe uses a 112 bb. #2 spindles can also be cup specific. The thickness of end of Bottom Bracket cups and the size of the ball bearings can also vary, so the distance between the spindle races can be different. Below are 2 pages of five from Sutherland's Handbook for Bicycle Mechanics 7th Edition; these are just for Campagnolo spindles so it should give you an idea what you are facing just hoping you can find something that fits.

Oops these
Sutherland's Handbook pages were deleted because they are copyrighted material. I see however smontanaro saw the pages, and was educated..

So the reason the races are different with the spindles you have is because they are designed for different cups and possiblly different size ball bearings.

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Old 11-05-12, 05:50 AM
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*argh*. Thanks for the education. It looks like I may never find a suitable bb/crank combination.
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Old 11-05-12, 09:41 PM
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Thank you for all the help with my bottom bracket/crank woes. As some of you know, I also asked on the Classic Rendezvous list (thinking I was more-or-less asking if someone had suitable parts to help resolve the dilemma, but not really coming out and asking for it, dumb, I know). At any rate, John Thompson's question about "how does it fit?", coupled with a Flickr album sent to me by Chas. Colerich on CR, pointed me in the right direction. See the attached image (Campy crank press fit on the Sugino spindle - no bolts). The fundamental problem I have is actually going to be on the drive side, since the drive side arm bottoms out without a bolt. (Maybe a pre-CPSC crank would work here - no bulge? My crank appears to be a 1985 SR.)

I've learned a lot in the past two days about crank/bb combinations and problems. The possibilities seem endless, and I'm pretty much only interested in cranks from a single manufacturer. I hope people didn't feel like I was wasting their time. I do appreciate the help. (The Sutherland's 6th edition on CD looks like it might find its way onto my Christmas wish list...)

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Old 11-06-12, 05:57 AM
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Originally Posted by smontanaro View Post
Thank you for all the help with my bottom bracket/crank woes. As some of you know, I also asked on the Classic Rendezvous list (thinking I was more-or-less asking if someone had suitable parts to help resolve the dilemma, but not really coming out and asking for it, dumb, I know). At any rate, John Thompson's question about "how does it fit?", coupled with a Flickr album sent to me by Chas. Colerich on CR, pointed me in the right direction. See the attached image (Campy crank press fit on the Sugino spindle - no bolts). The fundamental problem I have is actually going to be on the drive side, since the drive side arm bottoms out without a bolt. (Maybe a pre-CPSC crank would work here - no bulge? My crank appears to be a 1985 SR.)

I've learned a lot in the past two days about crank/bb combinations and problems. The possibilities seem endless, and I'm pretty much only interested in cranks from a single manufacturer. I hope people didn't feel like I was wasting their time. I do appreciate the help. (The Sutherland's 6th edition on CD looks like it might find its way onto my Christmas wish list...)

Skip


Skip, I saw your thread on CR and came here. There's an excellent directory of Campy crank/spindle/cup compatibility on the Bicycle Classics website, www.bicycleclassics.com. This still-active on-line store (with an ancient commercial web host) specializes in selling NOS vintage Campy, and Greg the proprietor has done a ton of research to construct the directory. To find what your crankset needs you start with the date codes on the back of the arms (site tells you how), and go from there.

Does your Medici have a 68 mm BB shell? The Ofmega spindle you have is for Italian, 70 mm wide. I don't know if you can re-assemble it onto the Bianchi, but it would be interesting to see if the Ofmega BB nailed the chainline on the Bianchi. If so, and if the Medici has the same BB dimensions, then whatever cups that came with the Ofmega spindle on the Bianchi should work correctly on the Medici. If you do re-assemble the Bianchi, take a ruler and see what the smallest clearance is, crankarm to chainstay and chainring or bolt to chainstay. Crank installation is essentially ruled by chainline (how the chainrings symmetrically align with the rear cogset whatever the type) and clearance to the frame (whether the crank or chainring are going to batter a hole in the chainstay as you ride). Spindle taper is ruled by whether the crank pulls on too far when torqued.

As far as whether an Avocet or Ofmega taper will effectively work with a Campy or other type of crankset, you could just try it and see what happens. If the crank starts to cover the base of the taper, that's too far. And if the end of the spindle is too close to the end of the taper hole when torqued, the taper on the spindle is too skinny. In both cases, the crank arm can be over stretched of the square hole distorted. In both cases, dead crank. Chainline has a spec, but it's not clear it needs to be met precisely.

Theoretically, at least, but I have made some Bride of Frankensteins work..
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