need advice: Dura Ace 7400 NJS bottom bracket

Hi,

Can someone advise me on NJS Dura Ace 7400 bb. I found out that NJS is a standard for track frames and which means that bb is BSA shell 68 and ISO square taper (not JIS which is a major square taper standard for Dura Ace 7400 bb). On ebay I found two types of NJS bb:

1) 68-112 which has NJS on both cups and NO NJS writing on the spindle
2) 68-109 which has NJS on both cups and also NJS writing on the spindle

Could someone knowledgeable advise me on this subject? Why the bb 68-112 has no NJS on the spindle? Why 68-109 has NJS on the spindle? Does it mean something for the user?

thanks a lot!

Tom

7400 is a road groupset, not track.

1) 112mm is the correct length for 7400 cranks fitted to British shells (113mm for Italian). But if the cups are stamped NJS, they aren't 7400 (which isn't to say they won't work with the spindle).

2) This is a track BB, but isn't 7400.

What I found about 68-112 spindle (without NJS writing on the spindle) is that it is not symmetrical. The difference is 3mm so my best quess is the one signed 68-109 (with NJS writing on the spindle) is symmetrical version?

But what is the difference in using of both spindles with such a small spindle lenght difference? Does someone know?

But what is the difference in using of both spindles with such a small spindle lenght difference? Does someone know?

Different cranks need different length spindles: if you use the wrong one, the chainline will be wrong.

You can use that to your advantage though. I'm using 7400 cranks with a 103mm BB on a fixed gear bike.

Please see this bb from ebay, the cups say BB-7400 NJS:

http://www.ebay.fr/itm/NOS-NIB-Shimano-Dura-Ace-7400-Bottom-Bracket-English-THREAD-68x112mm-NJS-PISTA-/261672454312?hash=item3cece4c8a8:g:DCgAAOSwnDxUcR2T

NJS = BSA cup threads & ISO square taper ( which is standard for track) & 68 shell

The question is why the lenght of spindle varies 112 vs 109mm?

Indeed they do! Which is confusing...

I can't find a 7600 BB: perhaps Shimano reused the 7400 BB cups for the 7600 cranks (which use 109mm BB), hence the need for an NJS mark?

Perhaps all 7400 cups were then marked NJS, so both the track (109mm) and later road (112mm) versions of the BB had NJS cups?

You have made a good point! Another puzzzle, here you have bb with 7400 NJS cups and 7600 NJS spindle... I wonder if this set is exactly how it was packed in the factory or it was the seller who mixed 7400 cups with 7600 spindle.

http://www.ebay.fr/itm/Dura-Ace-BB7400-Track-English-Threads-68mm-109mm-Square-Taper-Bottom-Bracket-JIS-/282092266567?hash=item41ae026447:g:9JwAAOSwQjNW95sJ

I think this bears out my theory that Shimano used 7400 cups to create a BB for the 7600 cranks.

If you search for "Shimano BB-7600", you won't find one (the later cartridge version is BB-7610).

I can't find a 7600 BB: perhaps Shimano reused the 7400 BB cups for the 7600 cranks (which use 109mm BB), hence the need for an NJS mark?>
Bingo, no such thing as 7600 cups, only 7600 spindle. 7400 cups come in British threading always marked NJS, also French and Italian - both non NJS.

A 7600 ensemble would probably cone without seals in the cups, a road set would though.

Hooray!

Someone who knows what they're talking about, rather me stumbling around the internet...

Thanks a lot both of you for involvement!

Well, I've learned something too!

Speaking of Shimano BB-7400, anyone has any tool or hints & tips on how to screw in the right side cup ? I.e. the one with 6 holes in it.
I think the ParkTool SPA-4 or HWC-18 are the correct tools, but would like to get a hand on one tomorrow and thus was looking for alternatives?

I need to install it on my Alan, but it doesn't screw in by hand (it stops mid way, may be because of dirt, tried to clean, but don't have proper cleaning tool either), so was thinking of a little help from such a tool.

Anyone?

HWC-18

You want the HCW-4 not the 18. An SPA-2 would also work as would any adjustable pin spanner with pins of the correct dimensions but the HCW-4 is the tool of choice really, anything adjustable will slip a lot more easily.

If t's dirt stopping the cup screwing in though, you really ought to give it a proper clean. A toothbrush and some degreaser/gt85/disc cleaner should be all you need really.

yeah, I think will do a proper clean before re-attempting it.

Thanks!

I have the HCW-4 if you need? I normally need it for the last few turns, but find that it's more useful for keeping the cup in the right place while tightening the lock ring.

Also have the HCW-5 (for the lock ring) if you need?

Cheers!

sent you a pm.

Much appreciated!

Hi there,
I know that is an old thread, but could somebody help me?Are the Shimano 7400 JD 1.37x24 BB cups BSA threaded?The axle is 112mm lenght.So is english threaded.
Thank you.