[Closed] Square taper campagnolo bb advice

No, the Shimano ones are JIS (Japanese Industrial Standard) which is a different taper.

I myself would use an ISO taper BB (which is what Campag are), but [url= https://www.sheldonbrown.com/bbtaper.html ]Sheldon Brown[/url] is less dogmatic.

If you have to buy a B.B. anyway just get the right taper to match but Shelton’s site does explain what happens if you mix iso and jis and it’s not death in a big fire ball

Well it's the difference between blagging one and buying one. For the turbo frankenbike...

What does happen if you mix them?

What does happen if you mix them?

All explained in the link slowster posted earlier.

(but for the lazy, the chainset will sit about 4.5mm further out than it would with a campag bb)

Yup, taper angle is the same but Shimano starts-out fatter - main problem would be that your double front mech cage might not swing wide enough (triple might work tho')

Needs to be an ISO BB. Also check axel length and buy the same.

There are several problems, which may and may not matter to you too much if the intended use is on a turbo-trainer.

Chainline will probably be wrong, as others have noted, the cranks sits further "out" if it's Campagnolo on Shimano (ISO on JIS), unless the tapers inside the crank are very worn - in which case you may get away with it (but I doubt it). This will have effects on shifting at the front & possibly give you problems on the big-big combination at the rear - the chain might tend to fall off inwards in this gear and maybe the next one, too - depends how worn other bits in the transmission are.

FD might and might not shift - but probably will. Bear in mind the same FDs are made to work with varying different diameters of seat tube so are not at a constant distance on every frame from the crankset anyway. The biggest problem would likely be on a 28.6 seat tube (trad steel) as the FD already has to throw further, without adding in the problem of an incorrect chainline / crankset 4 mm odd further out ...

Some possibility that in the long term the LH crank will split because there is not enough load-bearing surface engaged inside.

Thanks for all the info everyone.

Few things... yes it's on the turbo, I don't use the inner ring on the turbo as I use trainer road and the power is set according to the plan, I can spin a big gear and the turbo will adjust resistance to make sure wattage is correct.

So I'm thinking given the info from you helpful bunch of people..

I could go for a Shimano one with say a 113mm axle so that when it sits slightly wide it's not too bad.

Im going to fit an mtb mech and set the stop screws just so it's a chain guide for the top ring (prevent chain falling off under heavy loads or bounce).

Any thoughts on this as a plan?

Oh, and do you know if the frame is Italian or BS threaded ! Differing TPI's on the threads.

Bloomin' 'eck Graham you get everywhere!

My frame is English thread. It's a mash up bike to sit on the turbo trainer full time.

The used grouoset came with a campag bb but its italian thread and 68mm so no use