Gauging interest: Bottom bracket article at The Headbadge
07-15-11 | 12:49 AM
#1
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Gauging interest: Bottom bracket article at The Headbadge
The rendering rather suggests what I'm getting at - I'm considering adding a new page to The Headbadge explaining all the common bottom bracket oddities, including:
Thin cup vs. thick cup: How cups affect your spindles, and how to tell the difference
Offset spindles vs. symmetrical: Why the published width of your BB spindle won't tell you all you need to know
Crank offsets: Why two cranksets will give the same chainline with vastly different length BB spindles needs a much shorter BB spindle to give the same chainline
Cobbledegook: How to build a bottom bracket by matching a set of cups to an unrelated spindle.
Chainstay crimping: Compromising when your frame and choice of chainrings force you to move your cranks farther outboard than optimum chainline would suggest
Tapers: A database of what works, what doesn't, what works as a kludge, and figuring taper wear into your spindle choice
Installation depth: A subcategory of tapers - essentially, how to tell when your ISO crank has bottomed out (or when you've been torquing cranks way too much).
Any interest? If so, I'll proceed. If not, I won't bother.
-Kurt
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Last edited by cudak888; 07-15-11 at 08:31 AM.
07-15-11 | 12:56 AM
#4
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07-15-11 | 02:05 AM
#5
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From: Hurricane Alley , Florida
Bikes: Treks (USA), Schwinn Paramount, Schwinn letour,Raleigh Team Professional, Gazelle GoldLine Racing, 2 Super Mondias, Carlton Professional.
You can borrow my Sutherlands Book, the section on BB's has all the weird combos that work or won't work and why.
Mike
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07-15-11 | 06:11 AM
#6
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Just as long as you add a sub section devoted to converting Schwinn one piece cranks 
to three piece with the FMF or Truvativ conversion adapters. 
to three piece with the FMF or Truvativ conversion adapters.
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Bob
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Enjoying the GA coast all year long!
Thanks for visiting my website: www.freewheelspa.com
07-15-11 | 07:30 AM
#8
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Bikes: The keepers: 1969 Magneet Sprint, 1971 Gitane Tour de France, 1973 Raleigh Twenty, 3 - 1986 Rossins.
Likewise here. I've always managed to learn something, no matter how small, from yet another article on a subject.
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“No one in this world, so far as I know — and I have searched the records for years, and employed agents to help me — has ever lost money by underestimating the intelligence of the great masses of the plain people. Nor has anyone ever lost public office thereby.”
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Syke
“No one in this world, so far as I know — and I have searched the records for years, and employed agents to help me — has ever lost money by underestimating the intelligence of the great masses of the plain people. Nor has anyone ever lost public office thereby.”
H.L. Mencken, (1926)
07-15-11 | 08:04 AM
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-Kurt
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07-15-11 | 09:16 AM
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wow, what a resource that would be .. it would be very appreciated .... Thanks Kurt.
Scott
Scott
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07-15-11 | 11:11 AM
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I am a new member (been lurking for a while though), and relatively new to working on bikes. An article like this would be *very* helpful! I'm also interested in coverage of all of the options for converting the Schwinn Ashtabula one piece cranks to 3-piece. Thanks in advance.
07-15-11 | 01:24 PM
#20
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From: Dothan, AL
Bikes: 1971 Raleigh International; 1972 Raleigh International; 1971 Schwinn Sports Tourer
Please do it, I wouldn't have a situation I do now if this information had been available a few weeks ago. I just finished a complete restoration on a 1971 Raleigh International 23.5 inch frame (one obviously stripped for the components) and the bottom bracket was the greatest challenge. Had I not opted for a smaller inside chainring (42 tooth rather than the original 45 tooth) the inside chainring would be rubbing the rapid taper chainstay. I have precious little clearance, and could have used another millimeter of spindle length, but happily, everything works beautifully.
07-15-11 | 08:33 PM
#23
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From: Work in Asia, now based in Vienna, VA
Wonderful!
I remain quite mystified as to why a Stronglight 93 came with a 118mm Stronglight spindle, but fits easily onto a standard (pre-'77) Campy 114mm BB, and exactly which Phil Wood BB can be used?
Same with the mystery of the Avocet/Ofmega crankset that Sheldon says cannot be used with anything other than a special proprietary BB, but I ran for years on either a standard (again older) Campy BB or even longer on an OMAS (also standard ISO taper) BB?
Please, do write it.
Many thanks, in advance.
I remain quite mystified as to why a Stronglight 93 came with a 118mm Stronglight spindle, but fits easily onto a standard (pre-'77) Campy 114mm BB, and exactly which Phil Wood BB can be used?
Same with the mystery of the Avocet/Ofmega crankset that Sheldon says cannot be used with anything other than a special proprietary BB, but I ran for years on either a standard (again older) Campy BB or even longer on an OMAS (also standard ISO taper) BB?
Please, do write it.
Many thanks, in advance.
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1963 Hetchins Mountain King
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* 1971 Gitane Super Corsa (crashed)
* rebuilt as upright cruiser
1971 Gitane Super Corsa #2 (sweet replacement)
1980 Ritchey Road Touring (The Grail Bike)
1982 Tom Ritchey Everest
(replacing stolen 1981 TR Everest custom)
1982 Tom Ritchey McKinley (touring pickup truck)
1985 ALAN Record (Glued & Screwed. A gift.)
1959 Hilton Wrigley Connoisseur (my favorite!)
1963 Hetchins Mountain King
1971 Gitane Tour de France (original owner)
* 1971 Gitane Super Corsa (crashed)
* rebuilt as upright cruiser
1971 Gitane Super Corsa #2 (sweet replacement)
1980 Ritchey Road Touring (The Grail Bike)
1982 Tom Ritchey Everest
(replacing stolen 1981 TR Everest custom)
1982 Tom Ritchey McKinley (touring pickup truck)
1985 ALAN Record (Glued & Screwed. A gift.)
07-16-11 | 01:15 AM
#24
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I can't say that I'll be able to answer why you experienced some specific oddity, but perhaps phrase it in a way that will better explain the nuances.
That said, I was typing a bit regarding the thick/thin cup issue - I'm running this draft by you fellows for proofreading:
Not shown is a diagram indicating the B and D measurements, which I'll add later.
-Kurt
That said, I was typing a bit regarding the thick/thin cup issue - I'm running this draft by you fellows for proofreading:
Thin cup vs. thick cup:
Traditional bottom brackets of all threadings (or at least those in popular use) can be found in two different variants - thick-cup and thin-cup:
Components from each type should not be mix and matched with each other, as explained below:
Thick cups are usually 4.0mm in thickness from the outside face of the cup to the edge of the cup's bearing raceway (F); thin cups are generally 2.0mm, with some exceptions.
This means that a bottom bracket spindle made for thick cups will have raceways (B) spaced 4mm narrower than a spindle made for use with thin cups*. Even though bottom bracket sets of each type can be used to achieve the exact same overall spindle width (D) and offset, it is impossible to mix and match cups and spindles from each type. The differing cup and spindle thicknesses will result in the adjustable cup threading too far into the bottom bracket shell (thin cups + thick cup spindle) or sit too far outboard (thick cups + thin cup spindle). In theory, the latter combo can be used as a last resort, but there is a possibility that the left crankarm will bottom out on the cup.
Traditional bottom brackets of all threadings (or at least those in popular use) can be found in two different variants - thick-cup and thin-cup:
Components from each type should not be mix and matched with each other, as explained below:
Thick cups are usually 4.0mm in thickness from the outside face of the cup to the edge of the cup's bearing raceway (F); thin cups are generally 2.0mm, with some exceptions.
This means that a bottom bracket spindle made for thick cups will have raceways (B) spaced 4mm narrower than a spindle made for use with thin cups*. Even though bottom bracket sets of each type can be used to achieve the exact same overall spindle width (D) and offset, it is impossible to mix and match cups and spindles from each type. The differing cup and spindle thicknesses will result in the adjustable cup threading too far into the bottom bracket shell (thin cups + thick cup spindle) or sit too far outboard (thick cups + thin cup spindle). In theory, the latter combo can be used as a last resort, but there is a possibility that the left crankarm will bottom out on the cup.
Not shown is a diagram indicating the B and D measurements, which I'll add later.
-Kurt
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