Campag triple BCD

[mattsccm]

whats the BCD on the inner ring of a Campag triple c/s?

[Brucey]

74mm IIRC

cheers

[mattsccm]

Ta. just came back to say I had found it. 74mm

[fredN4]

74mm IIRC

cheers

please tell me what IIRC means.
Tks

[Brucey]

If I Recall Correctly

cheers

[ChrisButch]

What tends to catch you out is not so much the inner ring BCD (which it shares with others), but the middle, which limits you to a minimum middle ring size of 39 teeth. I assume this will continue to be the case with the newly-relaunched Campag triples, but I'm not sure. That limitation does quite severely restrict the versatility of the system: especially if you prefer the centre of gravity on your middle ring to be below rather than above the median point of your overall gear spread.

[Brucey]

the 'new triples' are listed with 39T middle rings and appear to have the same 135mm BCD as before. What isn't clear (to me, anyway, is how the new inner ring is attached. It might be that campagnolo have done it in a 'tripleizer stylee'; I have not seen any images of the inside of the new triples yet. Lots of pics of the outside on Campag's website etc.

http://www.campagnolo.com/jsp/en/newsdetail/newsid_282_newscatid_3.jsp

Also Athena EPS; I hope Campag do well with it; I don't think they can afford it to fail. Not that I'll be buying one anytime soon, mind.

cheers

[cycleruk]

the 'new triples' are listed with 39T middle rings and appear to have the same 135mm BCD as before. What isn't clear (to me, anyway, is how the new inner ring is attached. It might be that campagnolo have done it in a 'tripleizer stylee'; I have not seen any images of the inside of the new triples yet. Lots of pics of the outside on Campag's website etc.

http://www.campagnolo.com/jsp/en/newsdetail/newsid_282_newscatid_3.jsp

You might be right there Brucey? The shape of the middle ring gives concern as the section of the ring by the bolt hole looks to taper towards the hub center. Which either means the middle ring has a smaller BCD or as you suggest the small ring is mounted on it.

[Brucey]

if so, bring it on; I have an old Mirage UT double I want to convert; this way I can do it with genuine bits. I presume I shall have to knock the inner (new middle) ring tabs off the spider but there is no problem with that....

[edit, you can see the funny-looking middle ring here;

]

cheers

[RickH]

The diagram on p6 of this PDF suggests to me that the inner & middle share the same bolts on the new triple and also suggest that it may be harder to shrink the size of the inner (but not the middle).

Rick.

[Brucey]

good find, but I disagree with your interpretation. The spider for the big ring is a 135BCD and must lie between the middle ring and the big ring; (this is shown in some of the other illustrations). This will limit the middle ring to 39 min. , even if the middle ring isn't bolted to it (which I think it is in fact). The inner ring looks to be hung off the middle ring. This whole set up essentially looks like a tripleizer to me, but I guess we'll find out in the fullness of time.

cheers

[531colin]

I'm with Brucey, I reckon they are doing an "adapter ring" like this......(also available in 135mm, BTW)



Much cheaper than re-tooling for the crank, and there is no other reason for the middle ring to extend inwards past the 135mm bolt holes.

[Brucey]

this;

http://www.campagnolo.com/repository/documenti/en/GUARNITURA_TRIPLA_UK_06_12.pdf

has some more dwgs and tech specs of the Campagnolo 2013 Triple cranksets. It confirms 10s and 11s versions, with only two ratio choices, 50-39-30 or 52-39-30. As ever the outer chainrings are 135mm BCD in the specs, but it doesn't list the inner ring BCD.

However the dwgs show the inner ring bolts as being very close to the edge of the 30T chainring. This makes me think that BCD of the inner ring on the new triple is not 74mm. After a good deal of measurement I can exclusively reveal that (if their dwgs are properly to scale, which they should be these days) the 2013 Campagnolo triple inner chainring BCD is 94mm. 30T is the smallest ring that will fit this BCD.

'Bang,' then, I say. This is the sound of Campagnolo shooting themselves in the foot; having ostensibly offered something that might be useful to the randonneur or tourist, they have limited it to 30T on the inner ring, just eleven and a bit percent smaller than you can squeeze onto a 110 BCD compact double/triple anyway....

More bad news is that the middle ring is the same as the 'new style' inner ring on doubles, with the threads tapped into the chainring, which means it ideally needs different bolts etc. and maybe won't work with a conventional outer.

Chainline-wise we have 45.2 or 45.7mm; they have left the inner ring so that it is clear of the plane of the BB shell end. Obviously you won't necessarily be able to adjust it and maintain the cranks equally spaced from each side of the bike. On a steel frame the the chainline can usually be brought in another couple of mm which doesn't sound like much until you realise that this potentially translates to a 4mm reduction in the Q and U values.

So overall, nice try, but no cigar; if you want a Campag triple with a small inner ring (and without this choice, what is the point exactly???) it has to be an old ST one with a non-campag inner ring, or a 'new' triple with someone else's tripleizer chainrings.

Bang.

D'oh!

cheers

[cycleruk]

94mm ? That's the same as Shimano's new Ultegra triple inner BCD.

[531colin]

When were Campag. ever interested in touring cyclists?
I'm still using a pair of screw on hubs that refuse to show any signs of wear, let alone wear out.....but they started life hooked up to a SunTour rear mech. and Stronglight 100 chainset....we forget they only went down to 28 teeth, even TA Cyclotourist was 26 teeth, wasn't it?
22 and 24 tooth inners, which I use and applaud, were only made commercially available with mountainn bikes, I think? Before then, I saw the odd fixed cog grafted onto a chainset.....