Try Your Hand At Black Math!
#28
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When I was faced with this, I bought three cheapo shimano cartridge BBs- one like 103mm, one 110 mm long and one 117mm. For the $12 a pop, they've been nice to have in the partsbin anyway.
My plan was that once I settled on a size, I'd order something a little more upmarket than a shimano cartridge, but I forgot about it, and more exciting [and visible!] things came up to purchase, so it's still in there.
Uh, how do you adjust the length of a BB spindle?
Ok, I'm kidding, I know what you mean, but I've always been one to aim for the shortest BB axle I could get to work. I don't really know why, I guess I'm weirdly OCD like that and think that somehow 2mm over almost 3' is going to make a difference as to how my knees age.
My plan was that once I settled on a size, I'd order something a little more upmarket than a shimano cartridge, but I forgot about it, and more exciting [and visible!] things came up to purchase, so it's still in there.
Uh, how do you adjust the length of a BB spindle?
Ok, I'm kidding, I know what you mean, but I've always been one to aim for the shortest BB axle I could get to work. I don't really know why, I guess I'm weirdly OCD like that and think that somehow 2mm over almost 3' is going to make a difference as to how my knees age.
#30
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I ran a 111 JIS with a TA Pro-Vis. It was pretty near perfect. YMMV.
#31
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When I was faced with this, I bought three cheapo shimano cartridge BBs- one like 103mm, one 110 mm long and one 117mm. For the $12 a pop, they've been nice to have in the partsbin anyway.... ...Uh, how do you adjust the length of a BB spindle?
Ok, I'm kidding, I know what you mean, but I've always been one to aim for the shortest BB axle I could get to work. I don't really know why, I guess I'm weirdly OCD like that and think that somehow 2mm over almost 3' is going to make a difference as to how my knees age.
Ok, I'm kidding, I know what you mean, but I've always been one to aim for the shortest BB axle I could get to work. I don't really know why, I guess I'm weirdly OCD like that and think that somehow 2mm over almost 3' is going to make a difference as to how my knees age.
It's almost painful having to home-in on the optimum bb length/offset without having a few cartridge bb's at hand.
Even discarded, crunchy bb cartridges can suffice for figuring out the best fit with a safe minimum of chainring/chainstay clearance.
The shorter ones, less than 116mm (but also some longer than that) are symmetrical, simplifying the calculations.
I prefer using the shortest bb possible so that the pedal is harder to "dig" on the pavement in corners, and I prefer shorter crankarms, for this and other reasons.
Last edited by dddd; 04-12-13 at 12:16 AM.
#32
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I don't think finding the shortest workable axle is the exercise here, it's more like finding the clean chainline since this is a SS conversion. You may catch a pedal once in a blue moon but a sucky chainline with with you always.
#33
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Having several cheap cartridge BBs would be nice for these kinds of things. That said, I don't like the idea of repeatedly installing and removing nice, vintage, aluminum cranks.
Eventually I'd like to develop some sort of sixth sense regarding spindle selection. Kind of like putting a steak on the grill, grabbing a beer and then mid-conversation with someone just pushing them out of the way and pulling that steak off the grill because some bell inside me just rang and said "mid-rare. . . GO!". I think I'm a ways off from that, though.
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#34
incazzare.
Take video.
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#35
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A Miche Primato track bottom bracket worked for me. It has the same adjustability as Phil, but for a small fraction of the cost. The taper is ISO. My crank is a T.A., but I think the spindle length requirement is the same.
#36
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#37
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What gives? No Lagers, Triples or Scotch? Just sayin...make sure you have the proper tools on hand before you begin
#38
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#39
elcraft
I've got a similar problem. I want to set up a Stronglight 93 with a single front chain ring, but with the polished front trouser guard/chain guard, as well. In other words, the 45 tooth chain ring would be in the inner chain ring position. The rear hub, a Sturmey Archer Sprinter Elite 5 Speed, requires a 47 mm chain line (from the center of the seat tube). This was based on measuring from the dropout inner surface to the optimal cog position. I don't have the $$ to be buying multiple spindles to try out! If I were to use a JIS taper BB, what would the correct spindle length be? Black Math hurts my head!
#41
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It's a heap of a mess is what it is
#42
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I've got a similar problem. I want to set up a Stronglight 93 with a single front chain ring, but with the polished front trouser guard/chain guard, as well. In other words, the 45 tooth chain ring would be in the inner chain ring position. The rear hub, a Sturmey Archer Sprinter Elite 5 Speed, requires a 47 mm chain line (from the center of the seat tube). This was based on measuring from the dropout inner surface to the optimal cog position. I don't have the $$ to be buying multiple spindles to try out! If I were to use a JIS taper BB, what would the correct spindle length be? Black Math hurts my head!
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#43
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Here's what I'm working with.
I'm going to buy a JIS taper, symmetrical cartridge BB. Now, class, what length spindle would you choose?
- 120mm spaced frame
- Stronglight 49d crank arms with single 48t 3/32" ring
- Fixed/fixed hub with 1/8" cogs
- 68mm English BB shell
- 1/8" chain
I'm going to buy a JIS taper, symmetrical cartridge BB. Now, class, what length spindle would you choose?
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#44
Senior Member
OK then buy an adjustable BB with an offset spindle then you have about 10mm to play with
I've got a similar problem. I want to set up a Stronglight 93 with a single front chain ring, but with the polished front trouser guard/chain guard, as well. In other words, the 45 tooth chain ring would be in the inner chain ring position. The rear hub, a Sturmey Archer Sprinter Elite 5 Speed, requires a 47 mm chain line (from the center of the seat tube). This was based on measuring from the dropout inner surface to the optimal cog position. I don't have the $$ to be buying multiple spindles to try out! If I were to use a JIS taper BB, what would the correct spindle length be? Black Math hurts my head!
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