Campagnolo Cassette/Rear Derailleur compatibility

[Merida man]

Are there any problems with reducing the size of the from chainring from 39 to 34

 

[Smokin Joe]

Are there any problems with reducing the size of the from chainring from 39 to 34

You can't do it, 39t rings need a Bolt Circle Diameter (BCD) of 130mm and will only take a ring down to 38t. You'll need a compact chainset.

 

[Ajax Bay]

I have a 53/39 14/27 on my Campag 2000 Bianchi Road Bike.
. . . .
Are there any problems with reducing the size of the from chainring from 39 to 34

You have not shared what crankset you have. Need to confirm this (?Veloce) before answering the question authoritatively. Campagnolo standard BCD is 135mm and smallest chainring is a 39t.
Compact (ie with a 34t): https://www.campagnolo.com/UK/en/Components/veloce_crankset
Probably better off (vfm) with a non-Campagnolo compact chainset: the chain, derailleurs won't notice: get one which can use the current BB or buy a new one: they are inexpensive.

 

[2old2care]

No. It isn't.

How much difference would 0.21 of a mm make?

 

[2old2care]

Campag don't really do low bottom gear cassettes. Too cissy for those macho Italian men .
Your best option might be to find a triple front chainset but might be pricey, plus you'll need new FD and shifter. No, forget it, cheaper to lace a new Shimano hub and use their cassette. You can keep the RD.

Isn’t that what I said ? Sort of.

 

[winjim]

How much difference would 0.21 of a mm make?

The question is how much difference would 0.84mm make, since if you align it on the centre sprocket you've got four sprocket's worth of distance to travel in either direction.

If you really want to use a Shimano cassette you can take it apart and swap the spacers for Campagnolo ones since the sprockets themselves are the same width. Might require some force and a punch if the sprockets are pinned together.

 

[Yellow Saddle]

How much difference would 0.21 of a mm make?

The difference between index shifting and friction shifting, because if you align the chain with the smallest sprocket during set-up, as is custom, you'll increase the error for each subsequent sprocket by 0.21
2nd gear, 0.21mm out, 3rd gear, 0.42m out, 4th gear, 0.63mm out and so on.
In real terms this means only the default gear and the one next to it may give you any sort of gear, thereafter it is clatter and jumping and swearing.

Just accept it, it doesn't work.

 

[Ajax Bay]

lace a new Shimano hub and use their cassette. You can keep the RD.

@2old2care : "Get a Shimano wheel and a Shimano cassette. The nine speeds are the same spacing for Campag and Shimano, so should work."

Isn’t that what I said ? Sort of.

Yes, you reiterated what @Cycleops had already suggested (and which had been already contested as 'not compatible'). His advice was as useful as yours, in this instance.

 

[TheDoctor]

[Mod hat]
I've fixed the typo on the thread title
[/Mod hat]

 

[slowmotion]

If you want to search for some smaller chainrings, Spa Cycles is a good place to look. Just be sure to check that the bolt circle diameter will match.

https://www.spacycles.co.uk/

 

[Ajax Bay]

If you want to search for some smaller chainrings, Spa Cycles is a good place to look.

Agreed, and a TMN award to @boydj
Point (of the thread) is that one can 'look' but the OP's crankset can't take a chainring any smaller than their 39t.