Bicycle Mechanics - 1984 Nishiki BB size?

I must know what size BB to order for this bike. It is a 1984 nishiki international. The BB shell is 70mm wide. I measured with the cups and everything removed and I am positive this is the measurement. The right side (fixed cup) unscrewed clockwise, and the left side unscrewed normal (counter clockwise). It seems that every 70mm BB is itailian thread, but all the local bike shops tell me that I am crazy and that it has to be either 68 or 73mm. I want to order one soon as I prefer commuting on my bike, but it is out of commission right now.

thanks,
Jeff

you might want to bring the bike to your local bike shop and order the part from them. get the wrong part via the internet and your paying for return shipping, restocking and waiting.

English thread 68mm, spindle length to be determined by your crankset.

I must know what size BB to order for this bike. It is a 1984 nishiki international. The BB shell is 70mm wide. I measured with the cups and everything removed and I am positive this is the measurement. The right side (fixed cup) unscrewed clockwise, and the left side unscrewed normal (counter clockwise). It seems that every 70mm BB is itailian thread, but all the local bike shops tell me that I am crazy and that it has to be either 68 or 73mm. I want to order one soon as I prefer commuting on my bike, but it is out of commission right now.

thanks,
Jeff

It ain't italian if it unscrewed clockwise. The appropriate length bb depends on what crank you're using. Or if you're simply replacing the old one then measure it.

Sorry for the hijack , but I am getting ready to order a left crank for about the same vintage Nishiki bike. Is it a standard JIS taper??? (its for a Xmas present for a bike my Brother has, that his keeps getting loose on,,, tnks for any info...
Bud

English thread 68mm, spindle length to be determined by your crankset.


so is it some sort of "rule of thumb" to subtract 2mm from the measured width on BB's? It is 70mm on the caliper without a doubt.

That's bizarre! I've seen this a couple of times, English threading on a 70mm wide BB. Definitely takes English threaded cups. I ended up mixing and matching two different ball & cup BBs. Use an English one for the cups and take the "5" spindle from an Italian BB.

If you are looking to order a cartridge BB, an English BB may work on 70mm shell. There's typically about 2mm of gap & exposed threads on the left-side plastic cup anyway. So you'll just screw it in a little further. And most bikes of that vintage have asymmetrical spindle with a longer right-side anyway. So this 70mm with 2mm right-side offset may end up matching the original more closely than if you had a 68mm BB shell.

That's bizarre! I've seen this a couple of times, English threading on a 70mm wide BB. Definitely takes English threaded cups. I ended up mixing and matching two different ball & cup BBs. Use an English one for the cups and take the "5" spindle from an Italian BB.

If you are looking to order a cartridge BB, an English BB may work on 70mm shell. There's typically about 2mm of gap & exposed threads on the left-side plastic cup anyway. So you'll just screw it in a little further. And most bikes of that vintage have asymmetrical spindle with a longer right-side anyway. So this 70mm with 2mm right-side offset may end up matching the original more closely than if you had a 68mm BB shell.

so I should get a 73mm or a 68mm for the 70mm shell. I would think that 68 would be too small because the left side cup would have to be screwed in 2mm more than usual. So a 73mm would have about 3mm exposed on the left. Or I could put a BB cup spacer on the right fixed side to even it out a bit. right????

I'm pretty sure this thread should have stopped with Bob Barker's comment and/or a trip to the bike store, as we're just adding to the confusion. Buy a 68 mm bottom bracket with the appropriate spindle length and you should be fine.

"so is it some sort of "rule of thumb" to subtract 2mm from the measured width on BB's? It is 70mm on the caliper without a doubt."

No, it's just that unless your bike is Italian, or a higher end French bike (70mm), or the oversized MTB standard (73mm), 68mm is more or less THE STANDARD bottom bracket size, whether the frame manufacturers always adhere to the exact measurements or not.

http://www.sheldonbrown.com/bbsize.html#threading

so I should get a 73mm or a 68mm for the 70mm shell. I would think that 68 would be too small because the left side cup would have to be screwed in 2mm more than usual. So a 73mm would have about 3mm exposed on the left. Or I could put a BB cup spacer on the right fixed side to even it out a bit. right????

You're thinking much too hard.

If you're going to be using a 68 shimano square taper cart, this is a non-issue. The left cup either has a flange (metal) or it doesn't (plastic). If it doesn't have a flange tighten it in and it's fine, if it does and the flange bottoms out on the shell face before securing the bb then you can either

a) grind it off
b) find a metal lipless cup
c) insert 2mm spacer for the driveside

I had a 70mm japanese bianchi with english threads. I found a lipless cup and used it. The last option is to

a) face off 1mm from both sides of the shell

Most bb's hav a +/- 1mm shell width variation tolerance anyways.

THANKS. that explains it perfectly.

-Jeff