Bottom bracket size

[Dupont]

As long (no pun intended) as the cranks fit on ok and clear everything (frame and front changer) there's unlikely to be a major problem. Just a couple of minor adjustments to both mechs and cables will sort it out. Some folk here get really intense about 'correct chainline' but the odd couple of mm won't generally be a problem with a derailleur 'cos the chain is rarely running exactly in line. (I await a pelting with rotten veg!)

Well that has put my mind at ease. I guess technically we are looking at .75 mm difference either which when said like that doesn't sound too bad.

[geomannie]

I agree with fastpeddler, you should be fine with perhaps a few tweaks to the mech. One of my bikes (for reasons) I am running 1.5 mm off the optimal chain line with no issues.

[Dupont]

I agree with fastpeddler, you should be fine with perhaps a few tweaks to the mech. One of my bikes (for reasons) I am running 1.5 mm off the optimal chain line with no issues.

I imagine the front mech may need to be adjusted away from the frame just a fraction.

[Dupont]

Do I need to put any grease on the square taper part that accept the cranks when I put my new BB in?

There seems to be a differing of opinions from web searches I have done.

[fastpedaller]

I always put a smear of grease on the taper - but as you say opinions differ. I've never had a problem, but do ensure you tighten the bolts that hold the cranks to the axle to the correct torque (IIRC correctly 30-40nM). It's hand-hurtingly tight, but if a crank goes loose and is ridden any distance it will be ruined. No doom and gloom though, it seems you're coping well with the task.

[531colin]

No grease on the tapers. Crank and taper should be dry and seize together.
Seize is the wrong word, hopefully Brucey will be along

[Dupont]

I always put a smear of grease on the taper - but as you say opinions differ. I've never had a problem, but do ensure you tighten the bolts that hold the cranks to the axle to the correct torque (IIRC correctly 30-40nM). It's hand-hurtingly tight, but if a crank goes loose and is ridden any distance it will be ruined. No doom and gloom though, it seems you're coping well with the task.

Thanks. I am getting there. I have a torque wrench so will gets those bolts tightened up correctly.

[Brucey]

Do I need to put any grease on the square taper part that accept the cranks when I put my new BB in?

There seems to be a differing of opinions from web searches I have done.

the square taper joint is widely misunderstood. Roughly there are two schools of thought; those who follow shimano's stipulation to use grease and high torque,and those who follow campag's mantra of no grease and a lower torque value. So who is right? Well, I think they both might be.
You see it is easy to assume that because shimano's design looks superficially the same as campag's it is same. I don't think it really is. I think shimano's design intentionally allows some yield in the crank so that it resizes and it really fits the spindle. By contrast campag's parts are, I think, manufactured to better tolerances so fit one another better from the start, so no resizing is required. If I am correct, this explains the apparent mystery.
If as I suspect the tolerances are different in each case then probably it is best if you follow campag's advice when refitting the same crank on the same spindle and shimano's when fitting anything to any JIS spindle for the first time. What shimano don't tell you if that their procedure probably shouldn't be repeated incessantly, that the grease should under no circumstances be full of solid lubricants or extreme pressure additives, or that (if you push hard on the pedals) the cranks will probably cold-weld themselves onto the spindle in the longer term anyway.
So you may be thinking that shimano don't tell you much; well neither do campag really, it is 'omerta' all the way. What I do know is that regardless of the method used, it is not a bad idea to check the bolts within the first 100miles or so, retorquing to campags recommended torque if necessary. My suspicion is that this whole thing could be very greatly improved by the simple use of a drop of threadlock compound and a well-chosen belleville washer.

[Dupont]

I think as my BB is Shimano then I will apply a little copper grease to each taper and locking bolt.

[Brucey]

I think as my BB is Shimano then I will apply a little copper grease to each taper and locking bolt.

I believe that is absolutely the worst possible thing you could do. 'Copper grease' can contain all manner of things, but it always contains solid lubricants ie it is specifically intended to inhibit those processes which might allow your cranks to be retained if you pedal hard.

[rogerzilla]

The only difference between Shimano and Campag square taper (both considered obsolete by their makers) is that the Campag one starts narrower. They're both 2 degree tapers.

Grease on the tapers certainly affects the chainline - which is hit or miss for ST anyway, given manufacturing tolerances - but once you've had to remove seized cranks where the extractor has torn out of its threads, you use grease.

[Dupont]

The only difference between Shimano and Campag square taper (both considered obsolete by their makers) is that the Campag one starts narrower. They're both 2 degree tapers.

Grease on the tapers certainly affects the chainline - which is hit or miss for ST anyway, given manufacturing tolerances - but once you've had to remove seized cranks where the extractor has torn out of its threads, you use grease.

How does grease affect the chain line?

[Brucey]

what I suggest you do is first assess the fit quality between the cranks and the new BB. Typically this can be done by using a marker pen on the flats inside the crank, then trial assembling the parts, torquing the bolts to about half the usual torque before disassembly. The marker pen marks will show where there has been intimate contact or not. If the fit quality is good (all faces showing equal signs of uniform contact) then follow Mr Campagnolo. If however, the fit quality is less than perfect, use Mr Shimano's procedure, but be aware that you only have a few goes at this (resizing) before the cranks might fail.

[Dupont]

what I suggest you do is first assess the fit quality between the cranks and the new BB. Typically this can be done by using a marker pen on the flats inside the crank, then trial assembling the parts, torquing the bolts to about half the usual torque before disassembly. The marker pen marks will show where there has been intimate contact or not. If the fit quality is good (all faces showing equal signs of uniform contact) then follow Mr Campagnolo. If however, the fit quality is less than perfect, use Mr Shimano's procedure, but be aware that you only have a few goes at this (resizing) before the cranks might fail.

If all isn't right I will replace the cranks. They are S-ram hollow techs and they were very close to stripping threads on both sides when extracting them. I am not sure they would take another extraction.

[Brucey]

there is always a way of removing cranks, especially if you don't mind wrecking them because they are going to be replaced anyway. This means that you shouldn't let the possibility of damaged extractor threads put you off using a set of cranks.