70mm bottom bracket on a Japanese bike?
 

I picked up a Nishiki Sport (low-end) yesterday, and it had cottered cranks. I took them off, as I'm going to replace them with cotterless, and unpacked the BB. The cups were in perfect shape, so I just grabbed a different spindle and stuck it in there. When I put the adjustable cup back in, it screwed all the way in before elimating play in the spindle, leaving no room to screw on the lockring. I measured the shell, and it's 70mm. What the heck?

If I install the cups that belong with that spindle should it work?...I've always assumed you can mismatch spindles + cups, as long as the size is right. Maybe I could get an Italian 5-series spindle...

Do they even make 70mm english threaded BBs?

I'd bet it will........If the bb shell is 70mm, it's because of a slight flaw in the frame manufacture-

You haven't tried it with the right cups yet, so ?. If still short, replace with an Italian spindle or the whole thing with a cartridge BB where there's no lockring.

I had the same problem with a Fuji "special road racer". The shell was 70mm and there were only a few threads for the lockring. It held for quite a while, then suddenly came loose at the furthest point from home on a loop ride. Anyway, I had a LBS face the bottom bracket shell ($30), which got it down to 69mm. If you have access to an Italian spindle of the proper length, that would probably be a better/easier/cheaper solution.

maybe not. my entry level Fuji Sports 10 1978 bb is 70 mm too. And it has one of those 96mm front forks. Grrrh when it comes to upgrades.

My early 80s Fuji Sports 10 also had a 70mm, english threaded BB. I upgraded to a 68mm cartridge BB. The BB sunk in a bit past the shell when tightened, obviously, but I've never had any issues with it...

Important afterthought: when I did this upgrade I made the bike a single speed. Now that I think about it, doing this on a geared bike will probably present some problems...

Should not be a problem, as the side that threads in too deep is the non-drive side, so no effect on chainline, shifting, etc.

My friend recently got a job at our LBS, so I can probably get it faced for free. If I do that, the 1mm on the drive side shouldn't affect the chainline enough to matter, right? I don't want to have to buy a cartridge BB.

1mm or a little more won't kill you. Your FD should be able to handle that small difference. It would make more difference on a SS/FG, I'm assuming this is a geared bike.

It's not a manufacturing flaw, certainly. I've got an old Miyata frame, Japanese-produced, early-80's frame that has a 70mm, English-threaded bottom bracket. It came with cups that set the bearing surface 1mm inboard, and as such these cups stick out some extra distance when used on a 68mm shell (see attached picture).

If you want to use a modern BB with this, I'd say just get ti faced. Honestly, you can probably grind it down with a file - I'm going to do that with mine, only on the drive-side (as the stabilizing cup can thread in to where it's past-flush with the outer edge on the non-drive-side).

Actually, just filing it sounds like the easiest thing to do.

BB shells being not right on the 68mm spec is extremely common on older bikes. It's usually not a big deal. If you're using a cup-and-cone BB and there's no room for a locking, yeah, that's bad. In practice, it's usually just not a problem.

I just went down to the basement and checked some of my old road bikes' bottom bracket shell widths (I checked three '80's Schwinns, an '80's Centurion, and a '72 Raleigh). The only one that wasn't exactly 68mm was the one I consider my "highest end" bike, a 1972 Raleigh International. The bike came equipped with Campagnolo Nuovo Record cranks and bottom bracket, and the shell width is 66.5mm. Maybe it was originally 68mm and it's been faced, or maybe not, who knows. When I said in my earlier post the 70mm bottom bracket was a "slight flaw," clearly I should have said on older bikes these variations are a "characteristic" instead. And actually, with several reporting 70mm bb's on old Japanese bikes, it sounds like that particular width wasn't at all uncommon on those bikes-

So should I file just the non-drive side, or a little off of each? The "fixed" cup doesn't have a lip, so it's just like the other cup, and doesn't seat on the surface that would be filed.

I think you need to file just enough on the non-drive side so that the lockring can be screwed on, and that's it-

Well, it's worth measuring to see if the 70mm BB shell is symmetrical with the frame (if it isn't, then it's possible that the 70mm is a manufacturing defect, although I don't think that's the case).
I've never seen a fixed (drive-side) BB cup, on either a cup-and-cone system or with a sealed-cartridge BB, that doesn't have a lip. Are you sure you're talking about the drive-side cup?

Yup. I've never seen one like this either. The two cups are identical, except for the threading. I've seen a cup and cone BB with 2 adjustable cups for chainline issues, but both of the cups on that had lockrings, while this only had the one.

Then you might want to consider grinding 1mm off on the drive-side and updating to a modern BB?

Yeah, but that's not free:D I've got a few fixed cups sitting around, but if I'm going to use one then I don't want to file the drive side...I know I'm not going to get it perfect, and I feel like it would mess things up if the lip wasn't seated properly.

The reason I suggested filing only the non-drive side cup is that with your fixed cup without a lip, it doesn't sound like it would do any good to file the drive side, at least I think it would be more difficult to gauge how much to file off..........That does sound like an unusual fixed cup, in fact I don't see how it would really be a "fixed" cup without a lip to bottom against. You might try a different fixed cup, one with a lip, you might not need to file anything. If you do have to file it and you want to stay symmetrical, you could of course file equal amounts on both sides, but with just a couple mm I don't think it would make a noticeable difference-

That's what I was thinking. There wasn't a lockring on that cup, or room for one, so it seems like it would come loose pretty easily.