Gauging interest: Bottom bracket article at The Headbadge
 

http://www.jaysmarine.com/bb_and_spindles.jpg

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

If my Paramount doesn't qualify for the registry, am I allowed to say how cool and useful I'd find this?

Interest from me...although I suspect I've osmosed a lot of this already. But, by all means Kurt, I'd love to have such an article as a reference.

Of course.

Is yours a post-1984 Waterford, or did I forget to add you to the registry?

-Kurt

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

Just as long as you add a sub section devoted to converting Schwinn one piece cranks :rolleyes: to three piece with the FMF or Truvativ conversion adapters. ;)

:roflmao2:

I'd definitely read it Kurt.

Likewise here. I've always managed to learn something, no matter how small, from yet another article on a subject.

That should help when I get down to the oddball crank tapers.

It isn't particularly part of the article, but I recently aquired about 25 of those square taper spindles made to be installed directly into an Ashtabula BB (and use the Ashtabula bearing races).

-Kurt

I think that would be a great and useful article Kurt.

Dew eet!

I'd read it, although this may disuade you from wanting to write it.

Well, I've never quite digested all of those differences (thin vs. thick, etc.) when you've described them previously, but that's likely just me. Sutherlands is very useful for me, however.

Neal

+1

I find drawings, renderings such as your example pricelessly helpful.

wow, what a resource that would be .. it would be very appreciated .... Thanks Kurt.

Scott

Do it !

Another on the "I would read it" train. It would be great to have an article that puts all of that info into one place for me to try to finally make some sense of all of this BB stuff.

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.

Looks great!
Be sure to add cautions about fixed cups & casual attempts at removal.

+1

I've been working on a 10 speed conversion FAQ over on FGSS and this would be extremely useful.

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.

I'd read it with great interest, albiet I'm not anticipating needing to apply the information anytime soon; you never know.

It's settled then - I'll write the article. Give me a week or two; this one will take some time.

-Kurt

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 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:

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:

http://www.jaysmarine.com/thincup_thickcup_1.jpg

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.


http://www.jaysmarine.com/TH_BB_2.jpg

Not shown is a diagram indicating the B and D measurements, which I'll add later.

-Kurt

Very interested!

I like your drawings very much, Kurt.

Because of this thread, I re-read the stuff in Sutherland's 6th last night. There's a lot of dimensional info there, for replacing either whole BBs, or cups or spindle only; but it's difficult to sort through! For instance, I've been thinking of making a singlespeed out of a French-threaded frame, and I discovered that the "standard" Stronglight BB is one where the cups are pretty "out-there" compared to other makes, and the spindle is long in the waist. So in order to replace with a shorter track-length spindle (Stronglight or TA being seemingly ultra-rare in shorter lengths), I'd have to actually use an Italian spindle from Campagnolo, say -- not much more available, and expensive, too.

Their approach, categorically measuring spindles and cups, makes it much easier to find similarly-sized products. The concept of "shell (face) to end, right" or left is very useful, whether they invented that or not. What would be a useful next step is a cross-reference (re-sortable table) that would allow finding "roughly compatible" replacements. And vetting their information with measurements from other actual examples that people have.

With my head sort of numb from this, it occurs to me that V-O's JIS cartridge set with French cups might be well worth the $50!

I'd definitely read it, too. What I think would be useful is a simplified or more friendly presentation of all of the spindle length and assymmetry issues, in addition to a good presentation on taper and spindle/cup matching. Another open area is the assymmetries of cartridge BBs, and which ones are assymmetrical. Barnett's has a great procedure for determinimg the optimum JIS or other spindle to choose as a replacement, either as a wearout replacement, problem-solver, or a bike reconfiguration. If you can make all that stuff easier (and I don't think vids would help) without leaving out important stuff, that would be a great resource.

Charles, I dredged through all this in Suth and Barnett's a few months ago, to find a decent setup for a low-Q triple on a Trek 620. I went to a local LBS that had an old "box o' spindles," and bought a small handful to work with. I can confirm that the lengths (overall, center width, and right-end) quoted in both publications matched the spindles I had on the bench, to within about a half-millimeter. They are GOOD references. The procedures are complex and exacting (needs a good night's sleep fer sure), but I ended up with a Sugino/Suntour HS+G triple on the bike, 2 mm of minimum chainring-chainstay clearance, less than 2 mm of front chainline error, and a Q of about 155 mm. Many triples end up around 165 or worse. Now I need to optimize the rear hub positioning to get the rear chainline in-line.