Another Campy BB question - specialist knowledge required

so i;ve read the wise words of sheldon on bottom brackets and chainlines but have a query i;m hoping someone can solve.

Right, so i have a vintage campagnola strada chainset. The non branded tapered 120mm axle on the bb that's already on my frame has the chainline out (on the outer ring) by 8mm from the ideal 42mm! (it;s not too bad for the inner chain but i want a flushed finish on the chainset) so my thinking went... 8mm x 2 = 16mm... so i need to take that away from 120... so that leaves me with a desired 104mm axle length. is this correct?

I;ve looked about and it looks like i can get a 102mm campagolo chorus (i figured 1mm either side is acceptable) BUT I'm now holding off buying the bb because i read in another thread (http://www.londonfgss.com/discussion/2116/campagnolo-bottom-bracket-which-bloomin-one/#Item_32) that old campy stuff took 109mm axles.

Bearing in mind that the strada is a double chainring (and the thread referred to above was on about pista stuff) have i made the right calculation?

the other thing that crossed my mind (and forgive me if this sounds stupid) is whether all tapered axles have the same shape? I'm very much of the thinking that they do but as the paranoia has kicked in, now i;m concerned that if the campy spindle is different from the non branded one already on the bike then this would effect the position of the crank and render my calculation useless.

Not an expert, but I can offer this much from my own recent experiences.

Taper: Campag is ISO, ShimaNO etc is JIS. Check Sheldon for the implications of this.

The thread you refer to is for the Pista cranks, not the Strada so not necessarily relevant to you.

How old is the Strada crank? Older Campag cranks use asymmetric spindles.

The Miche BB is 107mm with ISO taper and has adjustable cups. You can find it online for a dozen sheets or so, and this might be the easiest way of getting set up.

My personal feeling is that you have to try and identify the Taper of the mystery BB first. If its JIS, the crank is going to be sitting much further out than with the equivalent ISO BB and secondly the cranks may be a deformed so you may have to a JIS BB. The best bet it is to pull the BB and look for manufacturers marks/stamps etc.

Also going to a really small 102 BB is probably the wrong thing to do, as you will probably move the crank way to inboard and most likely you'll have problems with the chainstays etc.

I ran a converted Strada crankset on a bike for a long time, and I think I had just the standard 109mm Campy BB down there (you could use a more modern 111mm as it only effects chainline by 1mm). As long as its the older fluted kind, I don't think theres a huge difference between the Pista, Strada and BMX fluted Campy cranks in terms of BB needed for a good chainline.

Oh and you may need to mill the chainring lips on the inside of the cranks off so they don't interfere with your chainstays. It really depends on the bike. Aside from that the Stradas are really nice cranks.

The taper on an ISO and JIS axles are different. Basically a Campag chainset will go on less on a Shimano BB and a Shimano chainset will go on further on a Campag BB. Many will say this makes them incompatible but as with many bike parts in practise they can work fine together. The only way I can get the chainline and clearance on my Chameleon SS spot on is by using a Shimano BB. The Centaur cranks take a little bedding in but it all works perfectly with no creaking or loosening.

Just to be clear I wasn't saying that you can't use ISO cranks on JIS BB:
http://www.sheldonbrown.com/bbtaper.html

Its just that it will deform the Campy crank, so if you use a Campy Crank on a JIS taper, you probably shouldn't then try and run the crank on an ISO taper. You may be able to get away with it, but its likely the fit will be poor, leading to creaking and other issues.

My advice still is for Protoype to identify the taper of the spindle his cranks are sitting on and use that for the basis for working out which BB he needs. It sounds like its probably ISO, otherwise the cranks would be really really far out - in which case any symmetric 109/111 bb ISO BB should do the job.

it's a lot of fuss to me getting a new BB if you can just use the inside of the double?! causing more headaches than are required, my 2p

I would guess that the BB you have is JIS. I think that the Campy Strada cranks take pretty much the same BB length as the Pista cranks since the front of them (and so chainline for outer ring position) is almost identical. That would mean a BB around 109mm, so if your 120mm BB was ISO then chainline should only be off by about 5mm, not 8mm.

I am pretty sure that a 102mm BB would be way too short for those cranks and I don't think they'd clear the chainstays.

I couldn;t get the bb off myself as the outer section was made of some sort of plastic and I fugures a metal lockring tool was not the best course of action for it. The frame is in for a respray and they're taking it off for me so i can;t check myself BUT i do remember thinking the cranks sat out a bit more than i expected on the axle. i;m thinking that would make it JIS. won;t get the frame back for two weeks so i guess it's a waiting game till them...

but this has been amazing advice guys. it's a solid amount of info for me to work on. thanks

http://en.wikipedia.org/wiki/Image:Campagnolo_Super_Record_chainset.jpg

Is this the chainset you've got? "Strada" just means "road" ie a double chainset, it's actually a Super Record, Nuovo Record had the same cranks but had different rings (to make even more confusing, earlier they were just called "Record"). The BB for it is 114mm, the track version of the Super Record/Nuovo Record BB was 109mm. If you fit the road cranks onto the track BB, the inner shoulder where the inner ring sits on will hit the chainstay, if you're only ever going to use it as a single ring chainset, you can file them off.
You can check if the tapers match by putting the crank onto the axle by hand and see how much the crank taper goes onto the axle. If it goes on about halfway or less, it's prob a JIS BB.

shit i forgot. on my polo bike i've got a campag triomphe crankset which i run on a 107 shimano BB (albeit with the drive side not fully inserted) and get perfect chainline, on inner ring (rear width 120mm and ambrosia hubs)

NOTE: i run my 42 ring instead of 52 in pic ;)

man it looks crap without the centre cap, got one now :)