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Can all crank arms be used with both bolt-type and nut-type bottom bracket spindles?

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Can all crank arms be used with both bolt-type and nut-type bottom bracket spindles?

Old 08-13-08, 01:48 PM
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dslfoolish
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Can all crank arms be used with both bolt-type and nut-type bottom bracket spindles?

I have an old Sugino GS crank on an old bike I'd like to put on a new build. Unfortunately, the BB appears to be dead and I'd like to replace it with a new cartridge bearing square taper BB. The thing is, the existing BB is of the solid spindle, nut-type as opposed to the bolt type I'm used to seeing.


According to the catalog http://equusbicycle.com/bike/sugino/index.html it suggests my crank (Sugino model DGS) can be used with the maxy spindles-- which I think are all JIS taper. I have seen the maxy spindles in both the nut-type and bolt-type styles, which leads me to believe crank arms don't care what kind of spindle it is, so as long as its square taper with the same standard.

Do the crank arms care what type is used? Is it design-specific? Or can I go ahead and get a new bolt-type BB with some generic crank bolts? I also read somewhere that occasionally the Type II (nut-type) spindles had a 3 degree (instead of 2) taper on the drive side. Is this true?
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Old 08-13-08, 05:13 PM
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DannoXYZ 
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You can see the difference in the taper-angle easily if you were to ever come across that super-rare 3-degree model. So I wouldn't worry about that.

Only compatibility question is between ISO vs. JIS. If you put the JIS Sugino crank onto an ISO BB, it may slide on too far and either touch the BB cups or the bottom out the tip and not be able to tighten the bolt. But both cases are extremely rare and you can pretty much install any crank on any BB.

If you were to get a new BB, the cheap Shimano cartridge ones are JIS and the Sugino crank will fit just fine. Only catch is those old BB-spindles aren't always symmetrical and you may need to install a spacer to move the new BB off to the right slightly.

http://www.sheldonbrown.com/bbtaper.html
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Old 08-13-08, 06:21 PM
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dslfoolish
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Thanks! Just out of curiosity, why did the old spindles used to be asymmetrical and not any longer? I know that making the drive side longer would allow room for the chainrings to clear the chainstays, but why isn't that done any more in modern BBs? After all, we still have the same chainring clearance issues with modern frames.

It seems making the BB spindles symmetrical now will simply require the non drive side crank arms to sit further out, increasing the Q factor...

Of course, there is a 99% chance that my reasoning is erroneous. I'm at work, anyhow.
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Old 08-13-08, 07:17 PM
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I have no idea but, assymetrical doesn't mean that the overall spindle length needs to be larger, most chainstays have a dimple in them to accomdate chainring sizes.

What chainring clearnace issue are you talking about?
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Old 08-13-08, 07:50 PM
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Originally Posted by dslfoolish View Post
Thanks! Just out of curiosity, why did the old spindles used to be asymmetrical and not any longer? I know that making the drive side longer would allow room for the chainrings to clear the chainstays, but why isn't that done any more in modern BBs? After all, we still have the same chainring clearance issues with modern frames.

It seems making the BB spindles symmetrical now will simply require the non drive side crank arms to sit further out, increasing the Q factor...

Of course, there is a 99% chance that my reasoning is erroneous. I'm at work, anyhow.
I think it is the result of better engineering. If you look at older square taper cranks, they look like cottered cranks without the cotter holes. The crankarms pretty much are straight beams from the center out. When cotters where used, there needed to be enough material outboard of the gear spider for the cotter holes and clearance to remove the cotters. Eventually that area of the cranks were moved inboard (with the benefit of increasing ankle clearance). The crankarms curve outward from the centers allowing them to use bottom bracket axle with less overhang (and potentially reducing the stress on the bearings). They have moved the axle/crank interface inward

As you tighten a tapered square crank it moves inboard and changes the "q-factor" and chain line. The amount of chainline clearance depends on the position of the chainstays and size of inner cog and how worn the tapers of the axles and cranks are. So axles of various lengths are available to crate the proper chainline. An advantage of newer systems is that the chain line is fixed relative to the bottom bracket so they can reduce the "q-factor" by putting the chain rings very close to the chainstays. The latest models have move the bearings outside of the bottom bracket shell allowing the use of larger axles and bearing in the same standard shell. The gear spider overlaps the bearings in order to produce low "q-factors"
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