Bottom bracket help needed!

Right, I've got some NJS Dura Ace FC-7600 cranks off Ebay and a 41mm (I think) chain line rear Atom hub, but it seems to be a bone of contention as to which BB spindle length is best!

From what I can find out from Mr. Sheldon, it seems the original BB was 109mm, but its virtually impossibly to find and not all BBs have the same taper.

The Shimano UN55 comes in 107mm or 110mm lengths, but have heard of others using 111mm Campagnolo BBs as well.

Would like a sealed, relatively inexpensive (£50 or less) BB to get my project going and will probably upgrade at a later point as needs be.

By the way, before everyone starts going mad, I have already checked the transmission database!

Well is it square taper?
I got told that you needed the miche BB for their crankset, which was a lie, so unless Shimano say you need a specific BB, just get a standard square taper from your LBS...

It is a square taper, but what length is the issue, as if its the wrong length, can put your chainring too far in or out and totally muck up your chain line, which could cause the chain to skip or even come off totally, which is not good!

Are the employees in your LBS not sound enough to let you try out a couple to see which fits best? Ask nicely

Tbh, the mechanic in my lbs is a bit shite and its run by an elderly couple who aren't very helpful, so I doubt it.

Plus, I'd rather order something a bit better, get it cheap online, and fit it myself.

Not having a car is a pain in the arse sometimes!

Have you got one to spare to slip into a frame? Try that and see the outcome

Nah, but as the UN55 BBs are only £15 a pop, if I grease up the spindle before fitting so it don't mark, I might be able to exchange it if its not the right size.

Yeah give that ago....

come on you two! or three! come on, guys, this is LFGSS.COM! i learnt everything i know form here! i am such a disappoint!

anyway. anything that bears NJS stamp on it is of a one unified standard. in case of cranks tapers / bb tapers, this standard is ISO (Campagnolo taper basically). so all NJS BBs will (should) have ISO taper. Shimano cheap shite don't have ISO tapers, they have JIS tapers. ISO tapers come from either NJS stamped BBs / Campagnolo BBs / Phil wood BBs / Miche BBs. Or this for instance.

on the axle length. yes, NJS drivetrains would run anything between 107 and 109.5mm, however you always have to bear in mind the way cranks sit on the spindle, the way you use chainring bolts, the way your frame chainstays are made, how worn the taper is on cranks etc. what i'm trying to say is, i'd rather go with longer spindle, than shorter one. in essence 111mm and 107mm axles have 2mm (two fucking millimiters!) of difference on each side of the cranks, given that track chain width is 3mm on the inside, you will barely notice that difference, and will have some extra space for future wear etc

/endrant

Thank you very much Scorch, it's people like you that make this site so invaluable for serious riders and builders!

Hadn't checked this in a few days, but fucking glad I did now.

One of my pet peeves is loose cranks as I've gone through about four sets due to this alone (I know, my fault for not tightening, it was a long time ago and I was young and riding a DH rig!) and generally avoid square taper like the plague, but I don't have the £300 odd for the Dura Ace 7700 cranks!

The Shimano cheap crap BB could have screwed up my cranks, so will go for something a bit more expensive like Campagnolo Centaur for now, and will think of you every time I don't have to replace em!

anytime

and use that ebay link above! that stuff is cheap and cheerful
also i think velosolo has those too

anyway. anything that bears NJS stamp on it is of a one unified standard. in case of cranks tapers / bb tapers, this standard is ISO (Campagnolo taper basically). so all NJS BBs will (should) have ISO taper.

Not necessarily. The 7710 Dura-Ace cranks use a splined octalink BB spindle.

thanks for the fill-in, very useful

=))

This is LFGSS.COM my friend.

pre 78 shimano cranks also use iso taper. with jis bb the crank will sit like 3mm more on the outside?? just buy a 111mm campa centaur or something. (cost me 20 euro)
it will fit somehow. if that doesnt work, use a miche pista bb. but be shure to use loctite for the cups.