I need to replace (at least) the spindle on a Dura Ace 7402 8-speed bottom bracket; the current one has crunchy pits where the bearings ride. The cups look OK, it's only the spindle that's graunchy.
I've scoured Sheldon Brown, used the search engine here, read and read, and become thoroughly confused. It seems this era Dura Ace is the odd "low profile JIS" spindle, and assymetrical to boot. On measuring, the drive side spindle is longer than the NDS. If I may ask the collective:

1. Can a standard JIS bottom bracket replace the entire unit? If yes, do I need to get something different from the 68 112 spindle length?
2. Are there current replacement "low profile JIS" bottom brackets out there?
3. Can a 70mm spindle be used in place of the 68 if I shim the cups?
4. Does anyone have a NOS Dura Ace 68 W spindle they'd like to part with?

P.S., admin, if this belongs in the "Classic and Vintage" section instead of "Bicycle Mechanics", please move the thread.

there are currently multiple used DA7400 BBs on Ebay, in various threading options. $35 to 60, used...

Thanks for the quick reply! I've seen those; f I'm tearing everything down, I'd like to put in something fresh, hence my queries for current/ new old stock alternatives.

So you would rather cobble together something screwed up just to have new parts rather than get lightly used correct parts????

If you want new, buy a Phil Wood. Otherwise, wait for a NOS English 7400 BB. Or buy something cheap with about the right spindle length and it will probably work fine once you put a 1mm spacer under the right cup.

I would buy used in an instant.

1- Most likely. The taper angles have remained fairly standard 2* for decades but the "thickness" of the taper has seen some variation. This is why if not replacing with an exact duplicate one really needs to test fit. How deep into the crank arm's taper does the different axle reach and where the rings end up are the two biggies that can be hard to completely predict.

2- "Low profile" refers to the crank arm, not any specific aspect of the BB spindle, excepting the difference in overall length spindle length. Low profile just means the crank arm has a "s" curve to locate the tapered hole closer to the frame, thus a shorter spindle is needed. By how much...

3- Yes

4- Not me. back then I was a Campy guy.

Sheldon Brown's website has had a very good description of all this and how to measure the spindle (not how far into the arm that spindle will fit, though). I strongly suggest doing a little bit of reading before you spend any $. Especially if you go used, where returns likely don't happen. Andy

Low profile JIS is indeed a spindle taper, not a crank description:




https://philwood.com/collections/squ...ottom-brackets

OK... so I did a cursory check of Fleaby and the results were somewhere between comical and tragic. There were several units with spindles so pitted to represent outright fraud. There were some mis-allocated track spindles. And finally, BBs that were a mis-mash of incompatible parts, particularly Italian and English. And of course the pricing was delusional as is the case on most vintage bike parts on Fleabay.

You want the English (68mm) spindles only. If your cups are fine, there is no reason to replace them; spindles always wear out first. Automatically refresh the 1/4" balls for the cost of like $5.

Recommendation: track down a Sugino MW-68 spindle. The same high quality as Dura-Ace, identical dimensionally, and a much better price. I am looking right now at Sugino and Dura-Ace spindles, and they are the same.

Look for a 3-? number/code.
Select a symmetrical equivalent if you're happy just to get a cartridge type and ride.

https://sheldonbrown.com/bbsize.html

I got a different impression (and thus more confused) by looking at the photos on the Sheldon Brown site. In these photos (from https://www.sheldonbrown.com/bbtaper.html)

it sure looks like the Low Profile JIS spindle has a shorter taper overall. https://www.sheldonbrown.com/bbtaper.html

Since I'm an old dog on a retirement budget, I've bought lots of used parts - that's not a concern. My only issue with buying used is that there's no guarantee the spindle races won't pit quickly again since I'm not aware of a simple way to measure wear of the hardened surface.

I've not used cartridge types in the past - can a symmetrical spindle of the correct length be adjusted for offset and chainline when using a cartridge bottom bracket? That might be the simplest course if I want something new.

You either put a spacer under the right cup to shift it in the direction that is longer, which is the drive side. Or you get a symmetrical spindel that is longer on the non-drive side so your drive side length is correct for chainline. Either is legit, but the first one only works reliably with cartridge BBs because there is no NDS lockring.

Well I guess I learned today. Serves me right for thinking like Sugino Mity Comp and Campy.

I do have a stash of mostly Campy and Sugino spindles from that era on my shelves. If I had the spindle's measurements (as Bill's chart shows) I would take a look for a possible close match. However how the taper would fit the arm and the resulting chainline (and frame clearance) can't be fully known long distance. Andy

The symmetrical equivalent is simply-
B+2C.
Since "C" is the part that determines crank placement, your work is done.

I'm still struggling to figure out how to use a symmetrical spindle to replace an asymmetrical one. Here's a photo of the existing spindle. Overall length is 112mm. A=29 B=52 C=31, so it doesn't match anything in the sheldon brown chart or the linked PDF from India.

I guess I'd look for a 112mm symmetrical spindle and offset it 1mm on the drive side, correct?

1mm of offset is a tiny amount, so little that as the crankarm settles onto the taper and is retorqued after initial use that 1mm offset might well "go away". Additionally as one increases the off set by shimming under the fixed cup the adjustable cup will be moving further into the lock ring by an equal amount. How much cup/lockring thread engagement is there now? How much can you loose as the cups travel to the bike's right and still have a secure lock ring tightening? This is where going to a 70mm spindle can be an asset. Those extra 3mm of bearing spread means you have 3mm of worry free shimming.

I'll look in my stash for any possibilities. Andy

why muck around?

Ebay Search: "Shimano Dura Ace BB-7400 Road Bottom Bracket JIS 112mm Spindle ISO Preowned
US $37.49"

or just the spindle, NOS. "Nos Shimano Dura Ace 70mm Bottom Bracket Spindle Bb7400 110mm
US $25.00/ea"

or a nice used one in 112... "EXCELLENT CONDITION Dura-Ace 7400 Bottom Bracket Spindle 68 x 112
US $32.97"

etc.

I have, on multiple occasions, used a standard symmetrical Shimano 112-113 sized bottom bracket for this typeof install.
Either sealed bearing or loose ball, both work just fine.

That ebay listing prompted of my initial questions: can I use a 70mm spindle in a 68mm BB and if yes, how?

Assuming the bearing surfaces are the same angles between English and Italian (no reason they wouldn't be), a 1mm spacer under your fixed cup should suffice. The lockring on the NDS can just screw in a little more, if necessary. They are only 1mm or so different in length, and that length is added between the 'cones' of the spindle.

Or it might be fine with no spacers at all. 1mm of variation in chainline is not important, and the NDS cup is threaded its entire width.

IF you can get the cups screwed on enough, is the "C" dimension the same?
Too far off and your FDER may not have the correct range??

You can buy a couple NEW, cheap cartridge units for what you want to pay for a USED spindle that nobody else will see.
Find out what size you actually need and when it dies, buy a "better quality" unit.
Somebody suggest a 112mm?

https://www.performancebike.com/shim...id=21892301670

Be Bold.. Man up and BUY SOMETHING.
you've been on Ebay.. and there are other sources of these BBs..
they even come up on FB marketplace and my local CL bike parts page at times.
they last indefinitely, if they are cleaned/greased occasionally, and don't get neglected....
yours looks like it was neglected in the rain, or ran at WAY too tight of an adjustment, prompting meltdown.

The previous owner replaced the DA BB with a generic Shimano. Yes, I think DA BB failed due to neglect; the bike sat for several years, the seatpost was difficult to extract and the quill stem is 100% seized in the fork, so the BB is only one of many small to-dos. The existing BB works OK. I'm asking all these questions because I'm trying to put the bike back to the original DA group, so I'm exploring options. Thanks, everyone, for the assistance!

So I located a spindle, ran the cups through the ultrasonic cleaner and discovered... Pitted cup races.

I appreciate the pointer to the Sugino spindle. Any words of wisdom on D-A cups?

I checked my stash and the onle close BB axle I have is a Campy NR 68-SS-120. It's aprox measurements are overall 112+mm, 30x50x33. How it might fit your DA arms I'll leave to an actual trial to see. But the tapers share the same angle and generally only how "thick/wide" and how long the tapers are is where the slight differences are. Hoe deep into the arm's taper will axle end up is also somewhat dependent of the wear/stretching of the arm holes.







PM me if you are interested in this axle. Sorry I have no available cups, the last of mine were made into frame painting handles. Andy

These are the cups I have on hand. There's a pretty clear wear track and some pitting. I'm just wondering if this is what I'll find in anything I can source.
Should I just reassemble with a newer axle and loose balls and hope for the best?