Tradarcher

I am putting a Sugino Super Mighty crankset on my univega and to get the right chainline I need a 113~114mm spindle in an ISO taper. From what I have read on Sheldon Brown's site I should be able to use a JIS spindle that's 4mm shorter or 109 correct? To simplify the process can I just get a 68x109 cartridge BB?

Ghrumpy

Just curious, how did you calculate your required spindle length? Is that the factory spec?

Hacking in a marginal solution isn't simpler or better than the correct one. Or maybe I just don't understand what's simpler about getting a 109 JIS than a 113 ISO (unless you have one sitting around.)
Taper is pretty important, length is pretty important. Even though the Super Mighty predates the ISO taper, it's essentially the same profile, so why wouldn't you just get the correct length ISO taper (or an original Mighty or Super Mighty BB) in the first place?

Tradarcher

Well i already have a 68x109 but if you can point me in the direction of a 68x113 or 114 iso cartridge bottom bracket that would be great

kc0yef 

oops I agree not ISO

Narhay

Try looking for a Sugino MW-68 spindle

JohnDThompson 

Factory spec for a Sugino Mighty double on a 68mm wide shell is an MW-68 spindle, which measures 114mm end-to-end.

SquidPuppet

I'm pretty sure that listing is wrong. I don't think Shimano makes ISO tapers.



Here is a 115 with ISO.

https://www.niagaracycle.com/categor...acket-68-x-115

Ghrumpy

Wish I could help with that.

If you want to go the easy route, that's none of my business. I'll just remind you to do your due diligence with dry fitting and making sure it's safe, so you don't regret it later. If you don't understand what that means, please don't be afraid to ask.

Narhay

Aren't modern ISO tapers not quite the same as Nuovo Record/Super Mighty tapers? That seemed to be the case when I was looking for a new cartridge bottom bracket and ended up going cup and cone.

Ghrumpy

Correct. ISO is a compromise taper. Close to Sugino Mighty, close to Campy, close to TA, close to Nervar, etc. Not exactly the same as any one of them. The end is a little smaller than most, so occasionally you have to grind the end to make it work with Stronglight. But it's also got a longer RH taper to accommodate TA, and also Stronglight, whose crank tapers are not symmetrical R-L.

JIS, on the other hand, is not a compromise taper. It's pretty much the Sugino Maxy taper, which was already the de facto Japanese spindle taper on all but the highest quality BBs and cranks. Sugino 75 still uses the Mighty taper, for example. The Maxy/JIS taper is actually pretty close to TA and Stronglight. Probably a copy of it, I'd guess.

SkyDog75

If I'm not mistaken, the MW-68 is 4 mm longer on the drive side. @Tradarcher may want to account for that asymmetry when selecting a replacement spindle. One way to do so would be to use a cartridge bottom bracket with the desired overall spindle length, along with a 2 mm spacer on the drive side. A spacer would effectively lengthen the drive side by 2 mm and reduce the non-drive side by 2 mm, matching the MW-68's 4 mm difference.

Tradarcher

So I should look for something like this?

https://rover.ebay.com/rover/0/0/0?m...2F173156929674

Narhay

Yes, but there are other options out there that don't cost $50. I got an NOS MW-68 spindle for ~$15 last year.

kc0yef 

PHIL

https://www.ebay.com/itm/Phil-Wood-6...sAAOSwjZ5andOy

Andy_K 

I think previous commenters have you on the right track, but I wanted to address this directly. What I have in bold here is not quite correct. What Sheldon says is that the crank will sit ~4.5 mm further out on a JIS spindle. You can't correct for that by simply getting a 4 mm shorter spindle.

Others have touched on the asymmetry of the original spindle, which complicates things significantly and is the reason that your best bet is probably to find an MW 68, since they are available.

Putting asymmetry aside for the sake of discussion, if both the original ISO and the replacement JIS spindles were symmetrical and you wanted to bring the drive-side crank arm in by 4.5 mm you'd need a 9 mm shorter JIS replacement because the change in length happens at both ends.

Now, if the previously quoted offset of 4 mm longer on the drive side is accurate (I don't know one way or the other), then a symmetric spindle of the same length would bring the cranks in 2 mm, leaving you another 2 mm to go, which you could achieve with a 4 mm shorter JIS spindle. That would theoretically put the NDS crank arm in a different place than the MW 68 would have it, but that may be acceptable (your knees will tell you if not).

So, if that offset is accurate, then your original proposal of a 4 mm shorter JIS bottom bracket might be just about right, though it got there by an indirect route. If you have a symmetric 109 mm JIS bottom bracket, I'd suggest giving it a try. It might just do the job.

Incidentally, this is mostly about getting the desired chainline and I would say that doesn't have to be spot on. As long as the derailleurs and your knees are all happy, it's close enough.

dddd

SkyDog75 is correct about the asymmetry.

The industry term for an amount of "offset" usually refers to the right end of the spindle protruding that amount (perhaps stamped as +1.5) further from the bb centerline than the left end of the spindle.This is quite different however than offsetting a symmetric spindle by that same 1.5mm, which results in the right end of the spindle then protruding 3mm further than the left end.

So we can use a symmetric cartridge bb an put a spacer under the fixed cup in some cases (as when the adjustable cup has no mini-flange interfering with it's further insertion into the bb shell), but must be aware of what (as in how much) we are trying to accomplish in terms of how far that both crankarms are positioned out from the bb shell faces.

The previously quoted figure of "4.5mm added to each end" of a JIS spindle's actual length to reflect it's effective length is incorrect.
The actual difference in overall effective length between same-length JIS and ISO spindles is very close to 4.5mm, so only one-half that amount is actually added to each end.
I believe that the error that I cited was due to someone using an assumed 2-degree included angle for the taper instead of the actual 2-degree angle off of the spindle's centerline (or 4-degree included angle), which would cause an error equal to 2x.

As for the tapers themselves, ISO is the taper used on all square-taper Campagnolo cartridge-style bottom brackets, of which many examples can be commonly found for use as a dimensional reference.
Oddly enough, the Sugino Mighty spindle taper is identical to this ISO standard.
And even more oddly, the Mighty bottom brackets were often a very good substitute for earlier Campagnolo bottom brackets, even though those pre-cartridge Campagnolo bottom brackets had a slightly wider-thicker spindle taper than the later ISO cartridge units.

I adopted a reference-point measurement method for locating a taper thickness measurement at a fixed and uniform distance from the end of the spindle, equal to the thickness of a caliper's jaws (typically 1/8"), since a caliper and spindle end can be easily pressed against any flat horizontal surface for easy field comparisons between any two or more spindle tapers. One would not want to be trying to measure the taper's thicknees at the very end of the spindle since many spindles have these corners rounded off. Note here that the actual thickness of one's caliper is not what is important if the same caliper is used for collecting all measurements, since we are only comparing thickness of the spindles (and then perhaps using a little trigonometry to equate these measurements to a spindle's effective length).

Pictured below is the practical field measurement method for comparing spindle tapers, where the thickness of the caliper's jaws defines the distance that each spindle taper is measured from it's end of the spindle.
The difference in thickness can then be equated to the difference in the effective length of each end of the spindle, i.e. how far that the crankarms are positioned out from the bb shell.

The formula to use when equating X (spindle end length difference) to 2Y (difference in overall thickness of the spindle ends) is: X = Y / Tan 2 Degrees. Note that is Y is only one half of the 2Y thickness difference since there are two tapers contributing to the thickness of the spindle end. Each flat is 2 degrees away from the centerline. 2Y is thus the thickness difference one measures directly.

Each .1mm of thickness increase thus adds 1.43mm of effective length to each end of the spindle.

A JIS spindle measures roughly .2mm thicker than an ISO spindle which adds about 2.85mm to the effective length of each end of the spindle, or 5.7mm to it's overall effective length.
I encourage anyone who is messing around with different tapers to do some of their own comparative measurements using a cheap digital caliper as shown.

dddd

Note that there is no real need to match the original crankset's asymmetry, since many of today's cranksets are symmetrically disposed in terms of each pedal's offset from the bb shell.

What is most important is the chainring's positioning.

A JIS taper will by itself compensate for the original spindle's offset on the drive side, so a same-length symmetric JIS bottom bracket should put the chainrings in nearly the same place, and with the pedals now symmetric about the bottom bracket shell. I dislike the old days setup of having the right pedal further out than the left pedal just to make room for the chainrings. Modern pedals have far more cornering clearance which reduces the advantage of moving the left pedal inward compared to the right pedal.

If the original bottom bracket gives ample clearance between the chainrings and the chainstay, I would consider using a slightly narrower JIS symmetric bottom bracket, which usually slightly improves the chainline and which can then be fine-tuned outward if needed with a fixed-cup spacer. The best of all worlds in other words, and what I have done myself many times.

CycleryNorth81

The original iso spindle is a campy copy, 115mm.
Sheldon Brown said an iso crank will go in further by 4.5 mm on a jis spindle per side, thus 9 mm per spindle.

New jis length= 115mm-(2x4.5mm)= 106mm

I would use a shimano UN55 (a sealed cartridge) with a spindle length of 107mm.

JohnDThompson 

Here's what I measure on an MW-68 spindle in my Pile 'o' Parts:





A = 30.0mm
B = 50.0mm
C = 34.0mm
D = 114mm

wrk101

See John's post above. This is why I usually keep a stack of spacers on hand, and sometimes put a 2mm spacer on the drive side to shift a symmetrical cartridge BB towards the drive side. Sometimes I need it, sometimes not.

dddd

Note what has been said about whether 9mm is accurate (it's not).
Better not to further advance false data unless you have done some measurements of your own which support it.
This topic has been coming and going for years here.

CycleryNorth81

I went through what the OP was trying to accomplish. I was assisted by a well known Chicago frame builder who has LBS and we came to the same conclusion. I resent that this is call false data.

Ghrumpy

You have that backwards. What Sheldon said was "If you install an ISO crank on a J.I.S. spindle, it will sit about 4.5 mm farther out than it would on an ISO spindle of the same length." [emphasis mine]
An ISO spindle taper starts smaller than a JIS, so a crankarm made to ISO spec won't press as far onto a JIS spindle.

(Let's also acknowledge that the Super Mighty isn't actually an ISO taper spec crankarm. It is close enough to fit well, but that fact may change the calculations a tiny bit.)

Even if your math works out, the problem is still the taper size, not the spindle length. On a crankarm taper as short as the Super Mighty, I'd rather have a well-fitted spindle and less unsupported crankarm, which will put more stress on a the unsupported bolt length as well. But that's just me.

I don't go along with Sheldon's reasoning behind why mixing tapers isn't a bad idea. Maybe it worked for him, but it's risky. And I would not take his recommendations on blind faith. He doesn't address the unsupported bolt issue that I mentioned. I've seen broken crank bolts caused by that.
The other, perhaps greater problem is that he divides the BB taper world into ISO and JIS, which might work for BBs and cranks made since about 1990, but ignores the reality previous to that. I'd advise everyone to be aware that that is an oversimplified view. You need not know every possible other taper dimension, but if you're working on C&V bikes, you should be aware they exist. Also be aware that those standards are voluntary, and not every crankarm or BB needs to be made to them.

This Super Mighty is from that previous non-standardized reality. Is that a problem? I can't say. Though useful, these generalizations are guidelines, but any specific implementation has to stand on its own merits of fit, especially when mixing brands or mixing pre- and post-ISO/JIS fitments.

When dry-fitted as tightly as you can get with your hand, and not tightened on, the spindle end should be about 3mm from end of the crank taper. Much more or less than that, and you might have problems. There should also be at least 2mm clearance between the back of the crank and the shoulder of the spindle (or the face of the BB cup) to allow it to tighten on. A little more is better.

CycleryNorth81

The math is correct. You would need to compensate for both side, not just the drive. Since I have not broken any crank bolts, cranks nor spindle, it works for me.

dddd

The problem is not the math in this case, which is simple. The problem is that you and Ghrumpy are both still going by a mis-stated figure of there being a 4.5mm difference in spindle insertion between JIS and ISO spindle tapers, which is demonstrably not the case.
I've provided the math equation and measurement method which anyone can use at home to make the comparison, so you don't have to rely on what anyone says. But I can tell that neither of you guys have measured the spindles we are talking about, but still going on what what was mis-stated in one single article ever, until that one article was quoted so many times because it has never been corrected by those who have control of the one web site. But maybe they leave it alone to test our abiity to agree to disagree, I don't know. It likely increases bottom bracket sales slightly, as a second purchase of a longer bb may be needed to keep one's chainrings from rubbing against the chainstay in some cases. Not what Sheldon intended, I'm sure.

And as for the Sugino Mighty spindle taper, I can't say what standard was used at the time these were manufactured, but they do in fact more closely match the ISO standard than any other spindles produced at that time. Measure for yourself and see, it's as if Sugino actually created the ISO standard which was later copied by Campagnolo when they started producing their ISO-standard cartridge bottom brackets. But the ISO standard has it's own history that we really can't know quite everything about.

When using an older Campagnolo or Stronglight crankset on a JIS spindle taper when the taper has obviously become enlarged, there will not even be 2mm of unused overlap of the square hole to supposedly cause broken bolts. Again, this can be proven when and if the OP selects a JIS spindle and fully tightens the old crank onto it, removes the bolt, and checks the space under the bolt head.

I'll make this my last foray into any taper discussions here on bikeforums. Either what I have patiently posted (repeatedly) gets traction, or it doesn't. Nobody seems to own and know how to use a caliper in these discussions. It's a boost to the forum anyway if these discussions and resulting "hits" traffic goes on ad-nauseum, and it won't be the end of the world if people resume going about finding these things the old-fashioned ways, before the internet. People here tend not to search out previous discussions before posting new question threads anyway, so I consider it wasted time. Long live the "extra 4.5mm" that a JIS spindle taper imposes on an ISO crankset's chainline then, just don't quote ME on it.